Parasitology Midterm Review

Lecture 2 - Nematodes (Part 1)

Learning Outcomes

Explain the mode of infection of nematodes in dogs and cats.
Describe the location within the host and life cycle of common nematodes of dogs and cats.
Explain diagnostic techniques for the identification of nematodes in dogs and cats.
Identify treatment and control measures for endoparasitism caused by nematodes.
Explain the zoonotic potential of certain nematodes.

Nematodes Morphological Characteristics

Unsegmented and circular in cross-section.
Bilaterally symmetrical.
Vary greatly in length.

Nematodes Reproductive Characteristics

Dioecious: separate sexes.

Nematodes Digestive System

Simple digestive system.

Nematodes Protective Layer

Acellular protective layer known as the cuticle.

Nematode Life Cycle

General Life Cycle Pathway

Eggs → Larvae (4 stages) → Adults.

Nematode Reproductive Strategies

Oviparous: Eggs contain single cells or morula.
Larviparous: Eggs hatch in utero, live larvae are borne.
Ovoviviparous: Eggs contain a larva.

Significant Orders/Superfamilies of Nematodes in Veterinary Medicine

Ascaroidea
Strongyloidea
Trichostrongyloidea
Rhabditoidea
Metastrongyloidea
Trichuroidea
Oxyuroidea
Spiruroidea
Dracunculoidea
Dioctophymoidea
Filarioidea

Ascarids (Roundworms)

Toxocara canis

Definitive Host: Dog
Common Name: Dog roundworm or ascarid
PPP (Prepatent Period): 2-4 weeks
Egg Larvation: Egg larvates (L3) in 3-4 weeks, temperature dependent.
Egg Size: 75 µm to 90 µm in diameter.

Mode of Infection for Toxocara canis

Ingestion of infective eggs.
Ingestion of a paratenic host (e.g., rodent).
Transmammary (encysted larvae from dam).
Transplacentally (encysted larvae from dam).

Life Cycle (Toxocara canis)

Parasite enters the body and migrates through various organs to the lungs, and into the trachea.
From the trachea, the larvae are coughed up and swallowed, then travel to the small intestines where they mature into adults.
Eggs are shed in the feces, and the cycle begins anew.

Toxocara cati

Definitive Host: Cat
Common Name: Cat roundworm or ascarid
PPP: 2-4 weeks
Egg Size: 65 µm to 75 µm.

Mode of Infection for Toxocara cati

Ingestion of infective eggs.
Ingestion of paratenic hosts (e.g., rodent).
Transmammary (encysted larvae from queen).

Life Cycle (Toxocara cati)

Parasite enters the body and migrates through various organs to the lungs and into the trachea.
From the trachea, larvae are coughed up, swallowed, and travel to the small intestine to mature into adults.
Eggs are shed in the feces, and the cycle begins anew.

Clinical Signs (Toxocara canis and Toxocara cati)

Pot-belly appearance.
Dry, lack-luster hair coat.
Underweight condition.
Vomiting.
Diarrhea.
Coughing (due to larvae migrating through lungs).

Diagnosis (Toxocara canis and Toxocara cati)

Fecal Floatation:
- T. canis – 75 µm by 90 µm.
- T. cati – 65 µm by 75 µm.
Eggs: Sub-spherical shape with thick, rough shell, each egg contains one or two cells when freshly passed.

Treatment and Control (Toxocara canis and Toxocara cati)

Treatment Options

Pyrantel pamoate
Fenbendazole
Milbemycin oxime
Moxidectin
Nitroscanate

Control Measures

Remove feces from the environment!

Zoonotic Concerns (Toxocara spp.)

Infection Route: Fecal-oral route.
Human Impact: Infect humans but do not mature.
Most susceptible population: children.
Conditions:
- Visceral Larval Migrans: larvae migrate through the liver, lungs, and central nervous system.
- Ocular Larval Migrans: impact on eyes.

Toxascaris leonina

Definitive Hosts: Dogs and Cats.
Common Name: Dog and cat roundworm or ascarid.
PPP: 8 to 10 weeks.
Egg Size: 75 µm to 85 µm in diameter.

Mode of Infection (Toxascaris leonina)

Ingestion of infective eggs.
Ingestion of a paratenic host (e.g., rodents).

Diagnosis

Fecal Floatation: Egg Size: 75 to 85 µm.
Eggs: Smooth, thick-walled colorless shell; zygote does not completely fill the eggshell; shell has a wavy internal membrane.

Treatment and Control (Toxascaris leonina)

Treatment Options

Pyrantel pamoate
Fenbendazole
Milbemycin oxime
Moxidectin
Nitroscanate

Control Measures

Remove feces from the environment.

Zoonotic Potential

Less likely compared to Toxocara spp.

Baylisascaris procyonis

Definitive Hosts: Raccoon and dog (rare).
Common Name: Raccoon roundworm or ascarid.
PPP: 7-10 weeks.
Zoonotic Potential: Yes.

Mode of Infection (Baylisascaris procyonis)

Dogs become infected via:
- Ingestion of larvated eggs.
- Ingestion of paratenic hosts that have consumed larvated eggs.

Conditions

Visceral and ocular larva migrans as well as CNS migration.

Control and Prevention Measures for Baylisascaris procyonis

Keep dogs on a leash.
Prevent predation and scavenging activities.
Limit ingestion of paratenic hosts or contaminated environments from raccoon feces.
Prompt removal of feces to help prevent ascarid eggs from remaining as fecal material decomposes/disperses.

Roundworms (Ascarids)

In North America, most cases of disease in humans are caused by Toxocara canis and Toxocara cati.
Some cases are due to Baylisascaris procyonis.
Most ascarid ova require 2 to 4 weeks in the environment to become infective, with the exception of T. leonina (1 week).
Ascarid ova are hardy and can survive and remain infective in the environment for years.

Hookworm (Strongyloidea)

Ancylostoma caninum

Definitive Host: Dog.
Common Name: Canine Hookworm.
PPP: About 2 weeks (depends on temperature and humidity).
Egg Size: 56 µm-75 µm by 34 µm to 47 µm.

Mode of Infection (Ancylostoma caninum)

Ingestion of infective larvae (L3).
Ingestion of a paratenic host (e.g., vertebrates and cockroaches).
Transmammary and transplacental (encysted larvae from damʼs tissues).
Skin penetration (larvae migrate through lungs afterward).

Ancylostoma tubaeformae

Definitive Host: Cat.
Common Name: Feline hookworm.
PPP: 2-4 weeks.
Egg Size: Slightly longer than A. caninum.

Mode of Transmission (Ancylostoma tubaeformae)

Ingestion of infective larvae (L3).
Ingestion of a paratenic host.
Skin penetration.

Clinical Signs (Ancylostoma spp.)

Anemia.
Diarrhea.
Weakness.
Melena.
Dermatitis (especially on feet).
Respiratory disease (from larvae migration).

Diagnosis (Ancylostoma spp.)

Fecal Floatation: Requires fresh feces due to ova larvating quickly.
Skin Biopsy (for dermatitis).

Treatment Options (Ancylostoma spp.)

Pyrantel pamoate
Fenbendazole
Moxidectin

Control Measures for Hookworms (Ancylostoma)

Clean up the environment; larvae do not live in the environment for more than several months and are killed by freezing temperatures.

Zoonotic Potential (Ancylostoma spp.)

Oral route of infection.
Skin penetration can lead to cutaneous larva migrans, a common travel-related skin infection in tourists to tropical areas.

Whipworm (Trichurida)

Trichuris vulpis

Definitive Hosts: Dog, fox, coyote (rarely cats).
Common Name: Canine whipworm.
PPP: 3 months.
Egg Size: 70 to 90 µm by 30 to 40 µm.
Adult Size: Approximately 75 mm.
Location: Adults live in the large intestine, burying whip-like anterior in the intestinal lining (consume blood).

Zoonotic Potential of Trichuris vulpis

Very low.

Mode of Infection (Trichuris vulpis)

Ingestion of infective ova.
Larvate in the environment for 10 days.
Larvated eggs hatch in the intestinal lumen, releasing larvae.

Diagnosis (Trichuris vulpis)

Fecal Floatation:
- Eggs: Thick, yellow-brown, with a symmetric shell and polar plugs (operculum) at both ends, unembryonated when laid.

Clinical Signs in Dogs (Trichuris vulpis)

Severe watery diarrhea and anemia in heavy infections; sometimes with hematochezia.

Treatment (Trichuris vulpis)

Treatment Options

Febantel
Moxidectin
Fenbendazole
Milbemycin oxime

Control Measures

Anti-parasitic treatment is essential, as they are extremely resistant to adverse environmental conditions and cleaning agents.

Similar Species

Trichuris felis: Feline whipworm.
Trichuris campanula: Other species with similar life cycles and clinical signs.

Stomach Worm (Physaloptera spp.)

Definitive Hosts

Dogs and cats, wild canids and felids (coyotes, foxes), raccoons, etc.
Intermediate Host: Insect.
Common Name: Stomach worm.
PPP: 58-83 days.
Egg Size: 42-58 µm by 30-42 µm.
Adult Size: 2-6 cm.

Mode of Infection (Physaloptera spp.)

Intermediate host (crickets, cockroaches, beetles) ingests the parasiteʼs eggs from the feces of the definitive host.
Eggs hatch in the gut of the intermediate host and develop into the third-stage infective larva.
Infection of the canine or feline definitive host follows ingestion of an infected intermediate host.

Location (Physaloptera spp.)

Found in the stomach or small intestine.
Firmly attached to the stomach; they suck blood and consume tissue from the hostʼs gastric mucosa, which can cause continued bleeding after detachment.

Clinical Signs (Physaloptera spp.)

Vomiting.
Anorexia.
Dark, tarry stools (melena).

Diagnosis (Physaloptera spp.)

Recommendation:
- Direct fecal smear or fecal sediment, as fecal floatation is unreliable due to the eggs not floating well.
- Look for larvae in vomitus or perform endoscopy (for adults).
Ova: Thick-walled, smooth, larvated eggs.

Treatment (Physaloptera spp.)

Treatment Options

Fenbendazole
Ivermectin

Veterinary Lab Techniques - Nematodes pt 2

Nematodes Overview

Nematodes are a diverse group of roundworms known for their segmented bodies.
They can inhabit various environments including soil, marine, and freshwater ecosystems.
Common species include Ascaris (intestinal roundworm), Ancylostoma (hookworm), and Dirofilaria (heartworm).
Diagnosis typically involves fecal flotation, where nematode eggs are isolated from feces for microscopic examination.
Other methods such as direct smear and Baermann technique may also be employed to identify the presence of adult worms or larvae in samples.
Additionally, serological tests can assist in detecting antibodies or antigens associated with nematode infections, providing a more comprehensive diagnosis.
Treatment options for nematode infections often include anthelmintic medications, which are designed to target specific life stages of the worms, disrupting their metabolic processes.
It is crucial to follow up with preventive measures, including regular deworming protocols and maintaining proper sanitation to reduce the risk of future infections.
Furthermore, educating pet owners about the signs of nematode infestations, such as weight loss, diarrhea, and lethargy, is essential for early detection and intervention.
A multi-faceted approach combining accurate diagnostic techniques, effective treatment, and preventive strategies can significantly improve outcomes for pets affected by nematodes.

Threadworm (Strongyloides stercoralis)

Definitive Hosts: Dogs, cats, and humans.
Common Name: Intestinal threadworm.
Adults: Found primarily in the small intestine, transparent and relatively small, typically measuring around 2 mm in length.
PPP: Approximately 8-14 days.

Mode of Infection (Strongyloides stercoralis)

Infection with Strongyloides stercoralis can occur through several routes:
- Skin penetration: The infective third-stage (L3) filariform larvae in contaminated soil can actively penetrate the skin of susceptible hosts.
- Ingestion of infective larvae: L3 larvae can also be ingested from the environment.
- Direct Transmission via Larvated Egg: In some cases, infective larvae can develop within the egg rapidly, leading to direct transmission if ingested.
- Transmission via milk from an infected dam to offspring is also possible.

Life Cycle (Strongyloides stercoralis)

Ova hatch in the intestine: The eggs are usually larvated and hatch rapidly within the host's intestine.
L1 larvae are then passed in the feces.
Once L3 larvae infect a host (via skin penetration or ingestion), they migrate through the body, often involving a tracheal migration route:
- Larvae enter the bloodstream, travel to the lungs.
- From the lungs, they move up the airway, are coughed up and then swallowed.
- They finally reach the gastrointestinal (GI) tract where they mature into adult worms.
Autoinfection: L1 larvae within the host can develop into L3 larvae, penetrate the intestinal wall or perianal skin, and re-enter the bloodstream without exiting the host.
This mechanism can lead to chronic infections and, in immunocompromised individuals, potentially fatal hyperinfection syndrome.

Clinical Signs (Strongyloides stercoralis)

Gastrointestinal signs: Severe diarrhea, often chronic, leading to weight loss and malabsorption.
Vomiting and anorexia may also occur.
Respiratory signs: During larval migration through the lungs, animals and humans may exhibit coughing, wheezing, and other respiratory distress.
Dermatitis: Skin irritation or dermatitis can occur at the site of larval penetration.

Zoonotic Potential (Strongyloides stercoralis)

Highly zoonotic, being a major causative agent of strongyloidiasis in humans worldwide.
Human infections can persist for decades due to its autoinfection capability, and hyperinfection syndrome can be life-threatening.

Diagnosis (Strongyloides stercoralis)

Identifying L1 larvae in fresh fecal samples is typical, as eggs hatch rapidly and are rarely seen.
Baermann technique: Effective for concentrating and detecting motile L1 larvae due to their active migration out of the fecal material.
Direct fecal smear: Can be used with lower sensitivity.
Fecal culture: Can be performed to allow L1 larvae to develop into L3 larvae for identification.

Treatment (Strongyloides stercoralis)

Treatment usually involves anthelmintic medications such as ivermectin, fenbendazole, or moxidectin, depending on the host species and severity of the infection.
Follow-up testing and environmental sanitation are crucial due to zoonotic and autoinfectious nature.

Heartworm (Dirofilaria immitis)

Overview

Order: Rhabditida
Definitive Host: Primarily dogs, occasionally cats and ferrets
Intermediate Host: Mosquito
Common Name: Heartworm
PPP: 6-8 months
Adults: Size: 15-25 cm long, found within the right ventricle and pulmonary artery.
Lifespan: 5-7 years in dogs; 2-3 years in cats.
Infections: New infections can occur during the patent period of existing infections.

Mode of Infection of Dirofilaria immitis

Infective Stage: L3 larvae transmitted by mosquitoes that have fed on infected dogs.

Clinical Signs in Dogs

Related to heart conditions, including:
- Syncope (fainting)
- Sudden death
- Coughing
- Vomiting
- Weight loss
- Dyspnea (difficulty breathing)
- Lethargy
- Anorexia (loss of appetite)

Life Cycle of Dirofilaria immitis

Mosquito ingests microfilaria: When a mosquito feeds on an infected dog, it ingests microfilariae (L1 stage larvae) circulating in the dog's bloodstream.
Development in mosquito: Within the mosquito's Malpighian tubules, the microfilariae (L1) develop into L2 larvae and then into infective L3 larvae over approximately 10-14 days. Ideal conditions are around 27°C (80°F), with development slowed at lower temperatures.
Transmission: When the infected mosquito subsequently feeds on another dog, the infective L3 larvae are injected into the subcutaneous tissues of the new host through the mosquito's proboscis.
Molting to L4: Within 1-2 days (approximately 48 hours) post-infection, the L3 larvae molt to the L4 stage within the subcutaneous tissues of the dog.
Development into young adults: The L4 larvae continue to develop and migrate through the subcutaneous and muscle tissues, maturing into young adults over a period of 50-70 days.
Migration to heart and pulmonary arteries: These young adults then migrate via the venous circulation to the right ventricle of the heart and the pulmonary arteries, arriving approximately 70-120 days post-infection.
Maturation and growth: Upon arrival in the heart and pulmonary arteries, the young adults typically measure about 2-4 cm long and rapidly grow to their adult size of 15-25 cm.
Reproduction and microfilariae release: Mature female worms in the pulmonary arteries begin to release new microfilariae (L1) directly into the bloodstream of the dog, marking the beginning of the prepatent period (PPP), which commonly lasts 6-8 months.

Diagnosis in Dogs for Dirofilaria immitis

ELISA Test: Enzyme-linked immunosorbent assay (Snap test) detects Dirofilaria antigen (from female worms over 6 months old). - High accuracy unless:
- Only immature female worms are present
- Very few adult parasites are present
- Only males are present
- Will not detect infections during the PPP.
Microfilariae Detection:
- Direct examination of fresh blood or blood treated with anticoagulant.
- Examination of liquid-cell interface (buffy coat) in a microhematocrit tube.
- Concentration via stained/unstained Millipore filter.
- Centrifugation modified Knott test (MKT).

Dirofilaria immitis in Cats

Infection Resistance: Cats show more resistance compared to dogs (considered atypical hosts).
Adult Worms: Generally, fewer than six adults present are typically of the same sex.
Diagnosis Challenges: Often goes undiagnosed due to circulating microfilariae not typically found in cats (occult infections). Even immature worms can cause lung damage.

Aberrant Migration and Clinical Signs in Cats

Aberrant migration of heartworms is more common in cats compared to dogs, potentially occurring in:
- Body cavities
- Systemic arteries
- Central Nervous System (CNS)
Clinical Signs: Usually associated with the arrival of worms in pulmonary vasculature or the death of adult worms leading to sudden death.

Diagnosis in Cats

Difficulties: Due to typically non-patent infections (very few or no adult worms).
Testing Preference:
- Antigen and antibody tests to detect exposure to heartworm larvae.
- Chest radiographs to identify changes in vascular structures or parenchymal inflammation.
- Ultrasound/Echocardiography to reveal the presence of heartworms.

Treatment

In Dogs: Melarsomine dihydrochloride (Adulticide).
In Cats: Treatment methods used for dogs cannot be utilized due to safety concerns. Prevention is the primary means of protecting cats.
- Goal: Stabilization through proper veterinary care.
- Preventive Medications include Ivermectin, moxidectin, selamectin, and milbemycin oxime.

Nematodes Targeting the Respiratory System in Dogs and Cats

Lungworm (Metastrongyloidea)

Aelurostrongylus abstrusus

Definitive host: Cats
Intermediate Host: Gastropods (slugs or snails)
Common Name: Feline lungworm
Adults: Size ranges from 4-9mm long (females are longer) and reside in the lungs.
PPP: 5-6 weeks.

Mode of Infection of Aelurostrongylus abstrusus

Infection Routes:
- Ingestion of intermediate hosts (snails, slugs).
- Ingestion of paratenic hosts (rodents, birds, frogs that have consumed intermediate hosts).

Life Cycle of Aelurostrongylus abstrusus

Adult Aelurostrongylus abstrusus female lays eggs in the alveolar ducts and terminal bronchioles.
Larvae are expelled: First-stage larvae (L1) emerge from the hatched eggs in the lungs.
L1 larvae are then coughed up, swallowed, and subsequently passed through the intestinal tract, exiting the cat's body with the feces.
Gastropods ingest the larvae: Terrestrial gastropods (snails or slugs) ingest the L1 larvae present in the cat's feces.
Development in the intermediate host: Inside the gastropod, the L1 larvae develop into second-stage (L2) larvae and then into infective third-stage (L3) larvae.
Cats acquire the infection by consuming either an infected intermediate host (snail or slug) directly, or by consuming paratenic hosts (such as rodents, birds, or frogs) that have ingested infected gastropods.
Once ingested by the cat, the L3 larvae penetrate the intestinal mucosa and migrate through the cat's body, primarily via the lymphatic and circulatory systems, aiming for the respiratory system.
The migrating larvae eventually reach the lungs, where they mature into adult worms.
- PPP: Approximately 5-6 weeks from ingestion of L3 larvae until L1 larvae appear in the feces.

Diagnosis of Aelurostrongylus abstrusus

Techniques:
- Baermann technique to locate first-stage larvae (L1).
- Analyze fresh fecal samples (noting sporadic shedding).
- Use bronchoalveolar lavage to recover fluids and look for L1s, identifiable by a “kinked tail.”

Clinical Signs of Aelurostrongylus abstrusus

Present as chronic cough, dyspnea (difficulty breathing), and wheezes.
Prevention: Limit cats from hunting potentially infected rodents and gastropods (snails, slugs, etc.).
Zoonotic Potential: Not considered zoonotic.

Eucoleus (Capillaria) aerophila

Order: Enoplida
Habitat: Primarily found in the respiratory system of various mammals, including dogs and cats.
Symptoms: Infected animals may exhibit respiratory signs, including coughing, wheezing, and difficulty breathing. Severe conditions may include pneumonia or bronchitis.
Transmission: Ingestion of eggs from contaminated soil or through the fecal-oral route.
Definitive host: Dogs and cats.
Common name: Lungworm of dogs and cats, feline and canine bronchial capillarid.
Adult worms: Range in size from 24-30mm and reside in the trachea, bronchi, and bronchioles.
PPP: 6-7 weeks.

Mode of Infection of Eucoleus (Capillaria) aerophila

Infection Routes:
- Ingestion of infective ova found in sputum or feces.
- Ingestion of paratenic hosts, such as infected earthworms.

Life Cycle of Eucoleus (Capillaria) aerophila

Eggs in sputum or feces are expelled (oral-fecal route).
Larvae from ingested eggs hatch in the small intestine and penetrate the mucosa, then migrate to the lungs via the bloodstream.

Clinical Signs (Eucoleus aerophila)

May be asymptomatic; however, heavy infestations lead to respiratory symptoms resulting from bronchiolitis and bronchitis (e.g., coughing, nasal discharge, dyspnea).

Diagnosis of Eucoleus (Capillaria) aerophila

Detection of Ova: Found in sputum or feces via:
- Fecal flotation techniques.
- Tracheal wash to extract samples.
Egg Morphology Distinction: Eggs often confused with Trichuris (whipworm) eggs; notable differences include:
- Size (smaller than T. vulpis)
- Color (lighter)
- Shape (more broadly barrel-shaped with asymmetric bipolar plugs).

Nematodes Targeting Dogs and Cats' Urinary System

Bladder Worm

Order: Enoplida

Pearsonema plica & Pearsonema feliscati

Definitive host: Dogs (P. plica), Cats (P. feliscati)
Intermediate host: Annelids (Earthworms)
Common name: Bladder worm
PPP: Approximately 2 months
Adult Size: Ranging from 13-60mm, residing in the mucosa of the urinary bladder.
Egg Description: Barrel-shaped, colorless, with thick striated shell and bipolar plugs.

Mode of Infection of Pearsonema plica & Pearsonema feliscati

Ingestion of infected earthworms or paratenic hosts believed to lead to infection through soil containing macerated earthworms.

Life Cycle of Pearsonema plica & Pearsonema feliscati

Eggs are shed in the urine of the definitive host: The adult male and female worms reside in the urinary bladder mucosa of the definitive host (dogs or cats), mate, and lay eggs that are passed in the host's urine into the external environment.
Development and ingestion by intermediate host: Outside, under suitable conditions, eggs embryonate and first-stage larvae (L1) develop within them over approximately 30 days.
Embryonated eggs are ingested by an obligate intermediate host (an annelid).
Within the earthworm's alimentary canal, L1 larvae hatch from the eggs, penetrate the intestinal wall, and migrate to the coelomic cavity of the earthworm.
They develop into infective third-stage (L3) larvae, typically over 2-3 weeks.
The definitive host (dog or cat) becomes infected by ingesting an earthworm containing these infective L3 larvae or via small rodents, birds, or frogs that have previously ingested infected earthworms.
Once ingested by the definitive host, the L3 larvae penetrate the intestinal wall and migrate via the lymphatic and circulatory systems to the urinary bladder.
Upon reaching the urinary bladder, the L3 larvae mature into adult male and female worms, embedding themselves in the urinary bladder mucosa, mating, and laying eggs. This completes the life cycle, with a PPP of roughly 2 months.

Diagnosis of Pearsonema plica & Pearsonema feliscati

Urine Sedimentation: Looking for amber, barrel-shaped, asymmetric bipolar plugged eggs (65 x 25 µm).

Clinical Signs

May be asymptomatic; potential signs of cystitis, dysuria, hematuria, and polyuria.

Treatment Options

Include Ivermectin and fenbendazole.

Giant Kidney Worm

Order: Ascaridida
Dioctophyme renale
Definitive hosts: Dogs, ferrets, otters, occasionally cats, horses, and cattle.
Intermediate hosts: Annelids.
Common name: Giant kidney worm.
Adult Location: Typically found in the right kidney; may also be free in the peritoneal cavity.
Adults can be bright red and over a meter long.
PPP: 5 months.

Clinical Signs

Ranging from asymptomatic to hematuria and/or signs of renal dysfunction.
Zoonotic Potential: Yes, it can be transmitted to humans.

Mode of Infection of Dioctophyme renale

Infection Routes:
- Ingestion of intermediate hosts (e.g., earthworms) or paratenic hosts (frogs, fish, crayfish) that have themselves consumed intermediate hosts.

Life Cycle of Dioctophyme renale

Infected definitive hosts produce eggs that are passed in urine.
Eggs are ingested by an annelid (intermediate host) and develop from L1 to L3.
Definitive hosts get infected by consuming L3 within the annelid or paratenic hosts.
L3-stage larvae penetrate the stomach, migrate to the abdominal cavity, and settle in the right kidney.

Diagnosis of Dioctophyme renale

Testing Methods:
- Urine sediment tests for eggs which are dark brown and barrel-shaped, measuring 65 x 42 µm, with opercula at both ends.
- The eggs have thicker, pitted shells compared to Pearsonema spp.

Clinical Manifestations

Can destroy kidney parenchyma, potentially leaving only the capsule intact.
Generally asymptomatic; may find eggs incidentally during spaying.
Possible signs include dysuria, hematuria, or lumbar pain.
Other tests may include ultrasound and IV pyelography; treatment often necessitates surgical removal.

Eye Worm (Thelazia spp.)

Overview

Definitive hosts: Dogs, cats, and other mammals
Intermediate host: Drosophila flies (fruit flies)
Common Names: Eyeworm
Adult Size: Ranges from 7-20mm long, appear white and exhibit rapid movement across the eye.
Adult Residence: Found in the conjunctival sac, tear ducts, conjunctiva, and under the nictitating membrane and eyelids.
PPP: 16-21 days.

Life Cycle of Thelazia spp.

Adult worms reside in the conjunctival sac of the definitive host.
Ovoviviparous females release L1 larvae.
L1 larvae are ingested by the intermediate host (fly) during feeding on tear fluid and lacrimal secretions.
Larvae develop to L3 in the intermediate host and migrate to the fly's mouthparts.
Upon the fly feeding on a new definitive host, the larvae invade the conjunctival sac and develop into adults.

Clinical Signs of Thelazia spp.

Symptoms include:
- Lacrimation
- Conjunctivitis
- Photophobia (sensitivity to light)
- Corneal opacity and ulceration.

Diagnosis of Thelazia spp.

Ova and Larvae Examination: Detection of ova and larvae through tears.

Treatment for Thelazia spp.

Use of local anesthetics for parasite removal with forceps.
Dewormers may also be applied to eliminate the infection.

Veterinary Lab Techniques: Cestodes Study Notes

Learning Outcomes

Explain the mode of infection of cestodes in dogs and cats.
Describe the location within the host and life cycle of common cestodes of dogs and cats.
Explain diagnostic techniques for the identification of cestodes in dogs and cats.
Identify treatment and control measures for endoparasitism caused by cestodes.
Explain zoonotic potential of certain cestodes.

Taxonomic Classification of Cestodes

Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda (Flatworms)
Other Related Phyla:
- Nematoda (Roundworm)
- Acanthocephala
- Trematoda (Fluke)
- Anthropoda
- Arachnida
- Insecta
- Protozoa

General Characteristics of Cestodes

General Structure:
- Cestodes are usually flattened dorsoventrally and commonly known as flatworms due to their cross-sectional shape.
Three Main Regions of the Cestode Body:
- Scolex: The head, which bears two to four suckers and may have hooks.
- Rostellum: The snout, potentially armed with hooks.
- Strobila: The body made up of segments (proglottids) following the neck, extending caudally from the head.

Characteristics of Adults

Ribbon-shaped organisms composed of many repeating segments.
Lack a body cavity and digestive tract.
Found exclusively within the host's digestive tract.

Classification of Cestodes

Subclasses of Cestodes:
- Eucestoda (True Tapeworms):
- Characterized by absorption of nutrients through their tegument and having at least one intermediate host.
- Cotyloda (Pseudotapeworms):
- Similar in nutrient absorption through tegument and also requiring at least one intermediate host.
- Differences in attachment methods: Eucestoda use suckers, while Cotyloda utilize bothria (slit-like organelles).

Life Cycle of Eucestoda

The eggs of Eucestoda contain a fully developed hexacanth embryo, also known as an oncosphere (so named because it contains three pairs of hooks).
Gravid proglottids filled with eggs are released into the feces.
These proglottids may rupture, releasing eggs into the environment, or be ingested whole by an intermediate host.
Intermediate hosts ingest the eggs.
Inside the intermediate host, the hexacanth embryo hatches, penetrates the intestinal wall, and develops into the metacestode stage (larval stage), such as cysticercus, cysticercoid, or strobilocercus, in various tissues.
The definitive host becomes infected after consuming the intermediate host, which contains the metacestode stage.
Once ingested, the metacestode's protoscolex evaginates, attaches to the small intestinal lining, and develops into adult tapeworms, producing strobili (chains of proglottids).

Life Cycle of Cotyloda

More complex due to having two or more obligate intermediate hosts in an aquatic environment.
Key Stages in Life Cycle:
- Adult worm produces operculated eggs (eggs with a lid) that are passed unembryonated in feces.
- Eggs must embryonate in water before hatching.
- A ciliated, free-swimming larva called a coracidium is released into the water.
- The first intermediate host, often a copepod (aquatic crustacean), ingests this coracidium.
- Inside the copepod, it develops into the first-stage larva, called a procercoid.
- The second intermediate host (often fish, reptiles, or amphibians) ingests the infected copepod.
- In this host, the procercoid develops into the second larval stage, the plerocercoid (or sparganum), typically found in the muscle or viscera.
- The definitive host then becomes infected after ingesting the second intermediate host containing the plerocercoid larva, which develops into an adult tapeworm in the definitive host's intestine.

Common Cestodes

True Tapeworms (Eucestoda)

Dipylidium caninum
- Definitive Host: Dogs, cats
- Intermediate Host: Flea, louse
- Common Names: Flea tapeworm, cucumber-seed tapeworm
- PPP: 1 month
- Characteristics: Most common tapeworm in dogs and cats, typically found in the small intestine.

Clinical signs of Dipylidium caninum

Symptoms include scooting, anal irritation, altered appetite, and visible proglottids on perineum.

Life Cycle of Dipylidium caninum

Flea larvae ingest eggs from proglottids.
Eggs develop into immature larvae (metacestode) in the flea.
Dog or cat ingests flea containing the immature larva.
Immature larva releases protoscolex upon ingestion, attaches to the small intestine, and develops into an adult with proglottids.
Gravid proglottids detach and are passed within feces.

Diagnosis of Dipylidium caninum

Finding proglottids on the pet, feces, or environment (appear as grains of rice when dry).
Squash prep of proglottid for microscopic examination.
Fecal examination using PCR or centrifugal flotation techniques; egg packets seen are 35-60 µm in size containing up to 30 eggs.
Note: Fecal flotation is less common due to the uneven distribution of proglottids in feces and large size of egg packets which have lower floating likelihood.

Treatment of Dipylidium caninum

Common treatments include Nitroscanate, Praziquantel, and Epsiprantel.

Taenia pisiformis

Definitive Host: Dog
Intermediate Host: Rabbit, hare
Common Name: Canine taeniids, rabbit tapeworm.
Characteristics: Adult can reach up to 200 cm in length and typically resides in the small intestine.
PPP: 2 months.
Clinical Signs: Potential intestinal blockage due to heavy burdens.

Life Cycle of Taenia pisiformis

Rabbit ingests tapeworm eggs.
Embryo develops into an immature larva (metacestode) in the rabbit.
Dog eats the rabbit which contains the immature larva.
Larva releases protoscolex that attaches to the small intestine lining and grows into an adult, producing proglottids.
Gravid proglottids detach and are passed in feces.

Diagnosis of Taenia pisiformis

Proglottids may be found in feces or on the pet, resembling rice grains when dried.
Examination includes squash prep of proglottids.
Fecal flotation to identify eggs specifically, which are round to oval approximately 38 x 32 µm with a hexacanth embryo.

Treatment of Taenia pisiformis

Treatment options include Praziquantel, Epsiprantel, Fenbendazole, and Nitroscanate.

Taenia taeniaeformis

Definitive Host: Cats
Intermediate Host: Rodents
Common Name: Feline taeniids, feline tapeworm.
Characteristics: Can reach lengths of up to 60 cm and resides in the small intestine.
PPP: 5-6 weeks.
Clinical Signs: May include irritation, changes in appetite, or mild diarrhea.

Diagnosis of Taenia taeniaeformis

Similar to other Taenia species: Finding proglottids in feces or on the pet.
Crush proglottids between slides to release eggs, measuring 30-40 µm in size.

Treatment of Taenia taeniaeformis

Recommended treatments: Praziquantel and Fenbendazole.

Echinococcus granulosus

Definitive Host: Dogs and other canids
Intermediate Host: Large herbivores including sheep, cattle, horses, moose; can also infect humans.
Common Name: Hydatid tapeworm.
Characteristics: Adults are small (2-9 mm) consisting of three proglottids (one immature, one mature, one gravid).
PPP: 50 days with adults residing in the small intestine.
Clinical signs: May include irritations around the anus, changes in appetite, and lethargy, often going unnoticed.

Life Cycle of Echinococcus granulosus

Eggs are shed in the feces of the definitive host (dog).
Intermediate host (e.g. sheep) ingests the eggs while grazing.
The embryos hatch and involve larval travel to various tissues (liver, lungs, brain).
Dogs ingest cysts from intermediate hosts.
Cysts develop into adult tapeworms in canids.

Diagnosis of Echinococcus granulosus

Eggs in fecal flotation are indistinguishable from those of Taenia species; thus, PCR or ELISA techniques are necessary.
Treatment in Dogs: Praziquantel and Nitroscanate.

Control Measures for Echinococcus granulosus

Prevent feeding of infected sheep or wild ruminant viscera to dogs.

Zoonotic Concerns of Echinococcus granulosus

Humans can act as intermediate hosts by ingesting eggs from contaminated produce or water, leading to Hydatid Disease.
Hydatid cysts can form in vital organs, potentially impairing function and causing severe complications requiring surgical intervention.

Echinococcus multilocularis

Definitive Host: Dogs and wild canids; cats less commonly involved.
Intermediate Host: Small rodents like shrews, voles, and field mice.
Common Name: Hydatid tapeworm.
Characteristics: Adult size ranges from 1-5 mm, residing in the small intestine, typically containing 4-5 segments.
PPP: 40 days.

Life Cycle of Echinococcus multilocularis in Intermediate Hosts

Post-ingestion of thick-shelled, embryonated eggs by a small rodent, the hexacanth embryo hatches in the small intestine.
The larval tapeworm then penetrates the intestinal wall, gaining access to the bloodstream.
The larva travels via the bloodstream, primarily to the liver, initiating development, and can disseminate to other vital organs.

Life Cycle of Echinococcus multilocularis in Definitive Hosts

A dog or other wild canid ingests the small rodent intermediate host infected with alveolar hydatid cysts.
Once ingested, protoscolices present within the hydatid cysts are released in the definitive host's small intestine.
Protoscolices evaginate, firmly attach to the intestinal lining, and rapidly develop into adult tapeworms, forming new proglottids.
Less than two months post-infection, gravid proglottids containing many infective eggs detach from the strobila and are shed in feces.

Diagnosis of Echinococcus multilocularis

Proglottids are too small to be observable.
Eggs measuring approximately 38-32 µm can be detected in fecal flotation or PCR techniques.

Treatment of Echinococcus multilocularis

Recommended treatments include Praziquantel and Nitroscanate.
Control Measures: Prevent dogs from accessing intermediate hosts.

Zoonotic Concerns of Echinococcus multilocularis

Conditions associated with the invasive growth of hydatid cysts leading to alveolar echinococcosis can cause significant liver damage and abdominal pain.
Advanced cases can lead to multi-organ failure.
The disease mimics malignant neoplasms such as liver cancer in infected host tissues.

Prevalence

Very common in Canada - 25% of the wild canid population in southern Ontario is infected.

Pseudotapeworms

Diphyllobothrium latum

Definitive Hosts: Dogs, cats, humans, and other fish-eating mammals.
Intermediate Hosts: 1st: Copepod (aquatic crustaceans); 2nd: Fish.
Common Name: Broad fish tapeworm.
Characteristics: Adults may grow between 3-25 meters and reside in the small intestine.
PPP: 4-6 weeks.

Life Cycle of Diphyllobothrium latum

Eggs are shed in feces.
Eggs must embryonate in water before being ingested by a copepod.
Developed larvae are later ingested by fish (the second intermediate host).
Definitive host consumes the fish, maturing the larva into a tapeworm which attaches within the intestines to develop proglottids.
Eggs are released from the proglottid and expelled in feces.

Clinical Signs of Diphyllobothrium latum

Common GI signs include vomiting, diarrhea, and weight loss.

Diagnosis of Diphyllobothrium latum

Detection of chains of segments in vomit or feces.
Fecal float or sedimentation techniques to identify operculated, light brown eggs.

Treatment of Diphyllobothrium latum

Primary treatment involves Praziquantel.

Zoonotic Concerns

Associated with Diphyllobothriasis in humans, a significant fish-borne zoonotic disease caused by the tapeworm.
Approximately 20 million people worldwide are estimated to be infected.
Clinical manifestations in humans may include abdominal pain, vomiting, diarrhea, and significant weight loss.
Transmission does not occur directly from infected cats and dogs to humans but rather through mutual consumption of undercooked or raw fish.

Spirometra spp.

Definitive Hosts: Domestic and wild carnivores, including dogs and cats.
Intermediate Hosts: 1st: Copepod; 2nd: Various reptiles, mammals, birds, amphibians.
Common Name: Zipper tapeworm.
Characteristics: Adults range approximately 1.5 m in length and reside in the small intestine.
PPP: 10 to 30 days.

Life Cycle of Spirometra spp.

The lifecycle parallels that of Diphyllobothrium latum, with multiple non-fish vertebrates as potential intermediate hosts.
Can use humans as paratenic hosts.

Clinical Signs of Spirometra spp.

Common symptoms include vomiting, diarrhea, and weight loss.
Larvae may migrate to subcutaneous regions, affecting eyes or CNS.

Diagnosis of Spirometra spp.

Identifying chains of segments in feces or vomit from infected animals.
Eggs approximately 60 x 36 µm can be seen in fecal flotation or sedimentation.

Treatment of Spirometra spp.

Treatment involves Praziquantel.

Zoonotic Concerns of Spirometra spp.

Known to cause Sparganosis in humans.
Humans contract the infection through the ingestion of infected copepods or immature larvae present in the tissues of intermediate or paratenic hosts.

Clinical signs in humans include gastrointestinal symptoms, with potential for larvae migration to other tissues such as subcutaneous regions, eyes, inner ear, urinary tract, pleural cavity, lungs, abdominal cavity, and CNS.

Cestode Treatment Chart

Praziquantel:
- Dipylidium caninum
- Taenia pisiformis
- Taenia taeniaeformis
- Echinococcus granulosus
- Echinococcus multilocularis
- Diphyllobothrium latum
- Spirometra spp.
Epsiprantel:
- Dipylidium caninum
- Taenia pisiformis
Nitroscanate:
- Dipylidium caninum
- Taenia pisiformis
- Echinococcus granulosus
- Echinococcus multilocularis
Fenbendazole:
- Taenia pisiformis
- Taenia taeniaeformis

Trematodes and Protozoa of Dogs and Cats

Trematodes Overview

Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Characteristic Features:
- Adults: Flattened dorsoventrally and unsegmented with a leaf-like shape, commonly referred to as “Flukes”.

General Structure of Trematodes

Symmetry: Bilaterally symmetrical.
Tegument: Tough protective layer against digestive enzymes.
Suckers: Two suckers for attachment to the host.
Digestive System: No real digestive system.
Reproductive System: Hermaphroditic (both male and female reproductive organs).

Life Cycle of Trematodes

Progress through several larval stages:
- Miracidium
- Sporocyst
- Radia
- Cercaria
- Metacercaria

Intermediate Hosts

One or more required, typically including a mollusk (phylum) or gastropod (class) such as snails or slugs.

Trematodes – Life Cycle Stages

Egg Stage: Eggs are operculated, containing a ciliated embryo known as a miracidium. Miracidia are released when eggs contact water.
First Intermediate Host: Miracidia penetrate a mollusk (often a type of snail) and develop into cercaria.
Second Intermediate Host: Cercariae are released from the snail and swim to enter a second intermediate host (usually fish, crayfish, or tadpole) to develop into metacercaria.
Definitive Host: The definitive host (e.g., dog) consumes the raw fish, where the parasite develops into an adult fluke in the small intestine. Eggs are produced and excreted with feces.

Common Species of Trematodes

Nanophyetus salmincola
- Hosts: Dogs, cats, and other mammals.
- First Intermediate Host: Snail.
- Second Intermediate Host: Salmonid fish.
- Common Name: Salmon Poisoning Fluke.
- Adult Size: Very small, up to 3 mm in length with one or two deep brown eggs in the uterus.
- Location: In the small intestine.
- PPP: 1 week.

Life Cycle of Nanophyetus salmincola

Fecal Excretion: Definitive host (dog) excretes eggs in feces, which mature in water into miracidia.
Development in Snail: Miracidia penetrate the snail skin and develop into cercaria.
Development in Fish: Cercaria emerge from the snail and infect fish, mainly salmon, sturgeon, or trout, leading to the metacercaria stage in the skeletal muscles.
Infection of Definitive Host: When raw fish is consumed, the parasite matures into an adult in the small intestine, where eggs are laid and passed with feces.

Clinical Signs of Nanophyetus salmincola

Symptoms: Generally mild gastrointestinal signs such as vomiting, diarrhea, lethargy, and anorexia.
Severe Risk: Can transmit Neorickettsia helminthoeca causing Salmon Poisoning Disease (SPD) in dogs resulting in hemorrhagic gastroenteritis.

Diagnostic Techniques for Nanophyetus salmincola

Fecal Sedimentation: Identification of gold eggs with operculum. Eggs are 50 to 80 µm by 30 to 55 µm.

Treatment

Praziquantel and epsiprantel.
Control: Prevent pets from consuming raw salmonid fish.
Zoonotic Potential: Accidental hosts but no risk of salmon poisoning in humans.

Alaria spp

Hosts: Dogs, cats, and other mammals.
First Intermediate Host: Snail.
Second Intermediate Host: Tadpoles.
Common Name: Intestinal Fluke.
Paratenic Hosts: Frogs, snakes, and mice.
Adult Measures: 2-4 mm in length, fleshy, and possessing wing-like alae, residing in the small intestine.
PPP: 5-6 weeks.

Life Cycle of Alaria spp.

Egg Release: Eggs passed in feces develop into miracidia upon hatching and penetrating a snail.
Cercaria Development: Cercaria exit the snail, infect tadpoles and develop into mesocercariae.
Infectivity of Tadpoles: Mesocercariae adhere and persist through to adulthood in the frog.
Paratenic Hosts: Mesocercariae can infect paratenic hosts (e.g., frogs) that consume infected tadpoles.
Infection of Definitive Host: Dogs consume infected tadpoles/frogs, leading to maturation in the small intestine.
Mesocercariae may also migrate to mammary glands via lactating queens during transmission to puppies/kittens.

Clinical Signs and Diagnosis of Alaria spp.

Diagnosis: Fecal sedimentation or flotation (sugar flotation effective).
Eggs are oval, light brown, approximately 120 × 65 µm.

Treatment

Praziquantel.

Protozoa Overview

Definition: Single-celled organisms.
Classification: Three Primary Phyla: Sarcomastigophora, Apicomplexa, and Ciliophora.
Infection Sites: Can infect various tissues; commonly detected in blood samples (hemoprotozoa) or fecal samples (intestinal protozoa).

Classification of Protozoa Based on Motility Structures

Flagellates: Use long, whiplike flagella.
Ciliates: Use cilia.
Rhizopods (Pseudopodia): Form temporary extensions for movement.
Sporozoans: Move through gliding, twisting, and bending.

Life Cycles of Protozoa

Reproductive Stages: Useful for identification; can reproduce asexually (binary fission, budding) or sexually (syngamy, conjugation).
Definitions:
- Trophozoite: The active, motile stage of a protozoan parasite capable of feeding and reproduction, primarily in the small intestine.
- Cyst: Transmission stage; metabolic functions are suspended for survivability in the environment.

Phylum Sarcomastigophora: Giardia and Trichomonas

Giardia spp.:
- Hosts: Most mammals.
- Stages: Trophozoite: Flagellates (motile feeding stage), pear-shaped, dorsoventrally flattened containing four pairs of flagella.
- Cyst Stage: Oval, refractile wall with four nuclei, also includes immature cysts.
- PPP: Variable but usually 1 week for cysts.

Life Cycle of Giardia spp.

Cysts ingested through contaminated water or feces.
Cysts release trophozoites in the small intestine, which attach to the intestinal wall.
Trophozoites divide by binary fission while some encyst and are excreted in feces.
Cysts can persist in environments for extended periods.

Clinical Signs and Pathology of Giardia spp.

Pathological Agent: Trophozoite is responsible for pathology.
Primary Signs: Diarrhea, which may contain mucus or fat; ranges from acute profuse, watery stool to soft stools.
Zoonotic Risk: Potential for transmission in both directions.

Prevention Methods for Giardia spp.

Prevent dogs from drinking untreated water.
Avoid high-density environments with young dogs.
Implement good waste management practices.

Diagnostic Techniques for Giardia spp.

Detection Methods:
- Fresh fecal smear (preferably warm with saline).
- Centrifugal flotation using zinc sulfate or sugar solution (cysts may be difficult to identify in fecal floats).
- ELISA for fecal antigen (Snap test).
- PCR testing.

Treatment

Metronidazole and fenbendazole.

Trichomonas spp. (specifically Tritrichomonas blagburni)

Definitive Host: Primarily cats, occasionally dogs.
Trophozoite Characteristics: Flagellates; pear-shaped (10-25 µm long, 3-15 µm wide), resides in the colon and cecum with four flagella (three anterior, one posterior).
PPP: Approximately 15 days.
Common in: Cattery cats, age of onset averages 9 months.

Transmission Route of Tritrichomonas blagburni

Shed trophozoites: Shed in feces; ingestion occurs during grooming or through contaminated food or water.

Clinical Signs, Diagnosis, and Prevention for Tritrichomonas blagburni

Symptoms: Chronic diarrhea lasting weeks to years, potentially containing blood or mucus.
Diagnosis Methods:
- Direct fecal smear
- Fecal culture
- PCR testing
Preventive Measures: Regular cleaning of litter boxes and isolation of infected cats.

Phylum Apicomplexa (Coccidia Life Cycle)

Oocyst: Tough, protective stage of coccidia containing a zygote (sporoblast).
Oocysts can survive long in the environment; when conditions are right, undergo sporulation, becoming infective.

Development Steps for Coccidia

Oocyst (contains sporoblast)
Sporoblast divides into 2 sporocysts
Each sporocyst divides twice, forming 4 sporozoites
Sporozoites = infective stage that causes infection in the host
4 sporozoites inside = sporulated oocyst = infective!

Cystoisospora spp (formerly Isospora spp.)

Hosts: Dogs and cats.
Species vary by host (e.g., Cystoisospora canis for dogs).
Common Name: Coccidia, causing coccidiosis.
Prevalence: Most prevalent protozoal diseases in puppies and kittens, rarely affecting mature animals.

Infection Mechanism of Cystoisospora spp.

Ingestion of sporulated oocysts or infected prey; oocysts produce sporozoites which invade intestinal epithelium.
- “Oocyst protects, sporocyst divides, sporozoites infect.”

Life Cycle of Cystoisospora spp.

Transmission: Ingested sporulated oocysts contain two sporocysts, yielding eight sporozoites that infect the intestinal epithelium and undergo asexual and sexual reproduction.
Recovery of Oocysts: Oocysts sporulate in less than a day under ideal conditions (30 to 37 °C).
PPP: 1 week.

Clinical Signs of Cystoisospora spp.

Signs: Watery diarrhea, sometimes with blood; risk of dehydration and death in young animals.

Diagnostic Techniques for Cystoisospora spp.

Methods of Diagnosis: Standard vial or centrifugal fecal flotation to detect oocysts, commonly round to ellipsoid in shape.

Treatment

Treatments: Sulfadimethoxine, ponazuril (compounded).
Control Measures: Reduce shedding of oocysts and implement environmental decontamination through heat, desiccation, and disinfectants.
Zoonotic Potential: Not known to be zoonotic.

Toxoplasma gondii

Definitive Host: Cats
Intermediate Hosts: Many warm-blooded vertebrates, including mammals and birds.
PPP: 1-3 weeks

Stages of Toxoplasma gondii

Oocysts: Resistant stages shed in feces, produced only by the definitive host (cats).
Trophozoites: Rhizopods, responsible for causing Toxoplasmosis in various hosts, including humans.

Zoonotic Concerns

Congenital infections in fetuses may lead to abortion, stillbirth, and disease in newborns.

Life Cycle of Toxoplasma gondii

Oocyst Shedding: Cats shed unsporulated oocysts that sporulate in the environment.
Pathway 1 (Minority): Cats ingest sporulated oocysts, undergo reproduction in the intestines, and excrete oocysts again.
Pathway 2 (Majority): Intermediate Hosts ingest oocysts, leading to the development of trophozoites that multiply in tissues; can also infect through the ingestion of tissue cysts or spores.

Clinical Signs and Management of Toxoplasma gondii

Diagnosis: Standard vial or centrifugal flotation, PCR, or serological tests for antibodies along with post-mortem detection of tissue cysts.
Treatment: Clindamycin, pyrimethamine, trimethoprim, and sulfamethoxazole.
Clinical Signs in Cats: Typically mild; young animals may exhibit fever, anorexia, cough, dyspnea, diarrhea, jaundice, or CNS signs.
Control Measures: Keeping cats indoors, ensuring pets only receive commercial/cooked diets; if raw meat is given, freeze it for at least 3 days to kill any tissue cysts. Regular cleaning of litter boxes is crucial to prevent oocyst sporulation. Pregnant women are advised to avoid contact with litter boxes or gardens where exposure is possible.

Medicine	Parasite (Scientific Name)
Clindamycin	Toxoplasma gondii
Epsiprantel	Dipylidium caninum, Taenia pisiformis, Nanophyetus salmincola
Febantel	Trichuris vulpis
Fenbendazole	Toxocara canis, Toxocara cati, Toxascaris leonina, Trichuris vulpis, Physaloptera spp., Strongyloides stercoralis, Pearsonema plica & Pearsonema feliscati, Taenia pisiformis, Taenia taeniaeformis, Giardia spp.
Ivermectin	Physaloptera spp., Strongyloides stercoralis, Pearsonema plica & Pearsonema feliscati, Dirofilaria immitis (preventive)
Melarsomine dihydrochloride	Dirofilaria immitis (adulticide in dogs)
Metronidazole	Giardia spp.
Milbemycin oxime	Toxocara canis, Toxocara cati, Toxascaris leonina, Trichuris vulpis, Dirofilaria immitis (preventive)
Moxidectin	Toxocara canis, Toxocara cati, Toxascaris leonina, Ancylostoma spp., Trichuris vulpis, Strongyloides stercoralis, Dirofilaria immitis (preventive)
Nitroscanate	Toxocara canis, Toxocara cati, Toxascaris leonina, Dipylidium caninum, Taenia pisiformis, Echinococcus granulosus, Echinococcus multilocularis
Ponazuril	Cystoisospora spp.
Praziquantel	Dipylidium caninum, Taenia pisiformis, Taenia taeniaeformis, Echinococcus granulosus, Echinococcus multilocularis, Diphyllobothrium latum, Spirometra spp., Nanophyetus salmincola, Alaria spp.
Pyrimethamine	Toxoplasma gondii
Pyrantel pamoate	Toxocara canis, Toxocara cati, Toxascaris leonina, Ancylostoma spp.
Selamectin	Dirofilaria immitis (preventive)
Sulfadimethoxine	Cystoisospora spp.
Sulfamethoxazole	Toxoplasma gondii
Trimethoprim	Toxoplasma gondii

Parasite (Scientific Name)	Common Name	Definitive Hosts
Aelurostrongylus abstrusus	Feline lungworm	Cats
Alaria spp.	Intestinal Fluke	Dogs, cats, and other mammals
Ancylostoma caninum	Canine Hookworm	Dog
Ancylostoma tubaeformae	Feline hookworm	Cat
Baylisascaris procyonis	Raccoon roundworm	Raccoon and dog (rare)
Cystoisospora spp.	Coccidia	Dogs and cats
Dioctophyme renale	Giant kidney worm	Dogs, ferrets, otters, occasionally cats, horses, and cattle
Diphyllobothrium latum	Broad fish tapeworm	Dogs, cats, humans, and other fish-eating mammals
Dipylidium caninum	Flea tapeworm, cucumber-seed tapeworm	Dogs, cats
Dirofilaria immitis	Heartworm	Primarily dogs, occasionally cats and ferrets
Echinococcus granulosus	Hydatid tapeworm	Dogs and other canids
Echinococcus multilocularis	Hydatid tapeworm	Dogs and wild canids; cats less commonly involved
Eucoleus (Capillaria) aerophila	Lungworm of dogs and cats, feline and canine bronchial capillarid	Dogs and cats
Giardia spp.	Giardia	Most mammals
Nanophyetus salmincola	Salmon Poisoning Fluke	Dogs, cats, and other mammals
Pearsonema plica	Bladder worm	Dogs
Pearsonema feliscati	Bladder worm	Cats
Physaloptera spp.	Stomach worm	Dogs and cats, wild canids and felids (coyotes, foxes), raccoons, etc.
Spirometra spp.	Zipper tapeworm	Domestic and wild carnivores, including dogs and cats
Strongyloides stercoralis	Intestinal threadworm	Dogs, cats, and humans
Taenia pisiformis	Canine taeniids, rabbit tapeworm	Dog
Taenia taeniaeformis	Feline taeniids, feline tapeworm	Cats
Thelazia spp.	Eyeworm	Dogs, cats, and other mammals
Toxascaris leonina	Dog and cat roundworm or ascarid	Dogs and Cats
Toxocara canis	Dog roundworm or ascarid	Dog
Toxocara cati	Cat roundworm or ascarid	Cat
Toxoplasma gondii	Toxoplasma gondii	Cats
Trichomonas spp. (Tritrichomonas blagburni)	Trichomonas	Primarily cats, occasionally dogs
Trichuris vulpis	Canine whipworm	Dog, fox, coyote (rarely cats)

Parasite (Scientific Name)	Life Cycle Type	Hosts	Mode of Infection
Aelurostrongylus abstrusus	Indirect	Definitive: Cats; Intermediate: Gastropods (slugs, snails); Paratenic: Rodents, birds, frogs	Ingestion of intermediate hosts (snails, slugs) or paratenic hosts (rodents, birds, frogs that consumed intermediate hosts)
Alaria spp.	Indirect	Definitive: Dogs, cats, other mammals; 1st Intermediate: Snail; 2nd Intermediate: Tadpoles; Paratenic: Frogs, snakes, mice	Consumption of infected tadpoles/frogs or paratenic hosts; mesocercariae may also migrate to mammary glands via lactating queens
Ancylostoma caninum	Direct / Indirect	Definitive: Dog; Paratenic: Vertebrates, cockroaches	Ingestion of infective larvae (L3), ingestion of a paratenic host, transmammary, transplacental, skin penetration.
Ancylostoma tubaeformae	Direct / Indirect	Definitive: Cat; Paratenic: (similar to A. caninum)	Ingestion of infective larvae (L3), ingestion of a paratenic host, skin penetration.
Baylisascaris procyonis	Direct / Indirect	Definitive: Raccoon, dog (rare); Paratenic: (hosts that consumed larvated eggs)	Ingestion of larvated eggs; ingestion of paratenic hosts that have consumed larvated eggs.
Cystoisospora spp.	Direct / Indirect	Definitive: Dogs, cats; Paratenic/Intermediate: Infected prey (non-obligate)	Ingestion of sporulated oocysts or infected prey.
Dioctophyme renale	Indirect	Definitive: Dogs, ferrets, otters, occasionally cats, horses, cattle; Intermediate: Annelids (earthworms); Paratenic: Frogs, fish, crayfish	Ingestion of intermediate hosts (earthworms) or paratenic hosts (frogs, fish, crayfish) that consumed intermediate hosts.
Diphyllobothrium latum	Indirect	Definitive: Dogs, cats, humans, other fish-eating mammals; 1st Intermediate: Copepod (aquatic crustaceans); 2nd Intermediate: Fish	Consumption of raw fish (containing plerocercoid larva).
Dipylidium caninum	Indirect	Definitive: Dogs, cats; Intermediate: Flea, louse	Ingestion of infected flea or louse (containing metacestode).
Dirofilaria immitis	Indirect	Definitive: Primarily dogs, occasionally cats and ferrets; Intermediate: Mosquito	Transmission of infective L3 larvae by mosquitoes.
Echinococcus granulosus	Indirect	Definitive: Dogs, other canids; Intermediate: Large herbivores (sheep, cattle, horses, moose), humans	Dogs ingest cysts from intermediate hosts; humans ingest eggs from contaminated produce or water.
Echinococcus multilocularis	Indirect	Definitive: Dogs, wild canids; cats less commonly involved; Intermediate: Small rodents (shrews, voles, field mice), humans	Definitive host ingests infected small rodent (containing alveolar hydatid cysts); humans ingest thick-shelled, embryonated eggs.
Eucoleus (Capillaria) aerophila	Direct / Indirect	Definitive: Dogs, cats; Paratenic: Earthworms (optional)	Ingestion of infective ova (from sputum or feces) or ingestion of paratenic hosts (infected earthworms).
Giardia spp.	Direct	Definitive: Most mammals (including dogs, cats, humans)	Ingestion of cysts through contaminated water or feces.
Nanophyetus salmincola	Indirect	Definitive: Dogs, cats, other mammals; 1st Intermediate: Snail; 2nd Intermediate: Salmonid fish	Consumption of raw salmonid fish.
Pearsonema feliscati	Indirect	Definitive: Cats; Intermediate: Annelids (Earthworms); Paratenic: Small rodents, birds, frogs (implied)	Ingestion of infected earthworms or paratenic hosts.
Pearsonema plica	Indirect	Definitive: Dogs; Intermediate: Annelids (Earthworms); Paratenic: Small rodents, birds, frogs (implied)	Ingestion of infected earthworms or paratenic hosts.
Physaloptera spp.	Indirect	Definitive: Dogs, cats, wild canids and felids (coyotes, foxes), raccoons; Intermediate: Insect (crickets, cockroaches, beetles)	Ingestion of an infected intermediate host.
Spirometra spp.	Indirect	Definitive: Domestic and wild carnivores (dogs, cats); 1st Intermediate: Copepod; 2nd Intermediate: Various reptiles, mammals, birds, amphibians; Other: Humans (as paratenic hosts)	Ingestion of infected copepods or immature larvae present in the tissues of intermediate or paratenic hosts (e.g., in humans).
Strongyloides stercoralis	Direct	Definitive: Dogs, cats, humans	Skin penetration by infective L3 larvae, ingestion of infective L3 larvae, direct transmission via larvated egg, transmission via milk from infected dam.
Taenia pisiformis	Indirect	Definitive: Dog; Intermediate: Rabbit, hare	Dog eats infected rabbit (containing immature larva/metacestode).
Taenia taeniaeformis	Indirect	Definitive: Cats; Intermediate: Rodents	Cat eats infected rodent (containing immature larva/metacestode).
Thelazia spp.	Indirect	Definitive: Dogs, cats, other mammals; Intermediate: Drosophila flies (fruit flies)	Larvae (L3) invade the conjunctival sac from the fly's mouthparts when the fly feeds on tear fluid.
Toxascaris leonina	Direct / Indirect	Definitive: Dogs and Cats; Paratenic: Rodents	Ingestion of infective eggs; ingestion of a paratenic host.
Toxocara canis	Direct / Indirect	Definitive: Dog; Paratenic: Rodent	Ingestion of infective eggs, ingestion of a paratenic host, transmammary (encysted larvae from dam), transplacentally (encysted larvae from dam).
Toxocara cati	Direct / Indirect	Definitive: Cat; Paratenic: Rodent	Ingestion of infective eggs, ingestion of paratenic hosts, transmammary (encysted larvae from queen).
Toxoplasma gondii	Direct / Indirect	Definitive: Cats; Intermediate: Many warm-blooded vertebrates (mammals, birds), humans	Cats ingest sporulated oocysts or intermediate hosts (tissue cysts); Intermediate hosts ingest oocysts; humans can be infected by oocysts or tissue cysts.
Trichomonas spp. (Tritrichomonas blagburni)	Direct	Definitive: Primarily cats, occasionally dogs	Ingestion of trophozoites shed in feces (during grooming or through contaminated food or water).
Trichuris vulpis	Direct	Definitive: Dog, fox, coyote (rarely cats)	Ingestion of infective ova.

Parasite (Scientific Name)	Egg Description (resemblance)	Adult Description	PPP
Aelurostrongylus abstrusus	Eggs laid in alveolar ducts. L1 larvae (first-stage larvae) with a “kinked tail” are recovered from feces via Baermann, not the eggs themselves.	$4-9 \text{ mm}$ long (females longer) and reside in the lungs.	$5-6$ weeks
Alaria spp.	Oval, light brown, approximately $120 \times 65 \text{ µm}$ operculated eggs.	$2-4 \text{ mm}$ in length, fleshy, and possessing wing-like alae, residing in the small intestine.	$5-6$ weeks
Ancylostoma caninum	Ova are $56-75 \text{ µm by } 34-47 \text{ µm}$ . They larvate quickly, requiring fresh feces for detection.	(Not explicitly detailed in terms of adult morphology, but implicated in causing anemia in the small intestine)	Approx. $2$ weeks
Ancylostoma tubaeformae	Ova are slightly longer than A. caninum.	(Not explicitly detailed in terms of adult morphology)	$2-4$ weeks
Baylisascaris procyonis	Ascarid ova are hardy and become infective in $2-4$ weeks. (Specific dimensions not given, but generally thick-shelled and embryonated like other ascarids.)	(Not explicitly detailed in terms of adult morphology)	$7-10$ weeks
Cystoisospora spp.	Oocysts, commonly round to ellipsoid in shape. (Unsporulated oocysts contain sporoblast, which sporulates to $2$ sporocysts, each with $4$ sporozoites).	Not an adult worm; protozoan stages are trophozoite and oocyst.	$1$ week
Dioctophyme renale	Dark brown, barrel-shaped eggs, $65 \times 42 \text{ µm}$ , with opercula at both ends. They have thicker, pitted shells (distinguishes them from Pearsonema spp. eggs).	Can be bright red and over a meter long, typically found in the right kidney.	$5$ months
Diphyllobothrium latum	Operculated eggs (with a lid) that are passed unembryonated in feces; they must embryonate in water. Light brown. (Similar to Spirometra spp. eggs).	May grow between $3-25$ meters and reside in the small intestine.	$4-6$ weeks
Dipylidium caninum	Eggs are found in packets (up to $30$ eggs) and are $35-60 \text{ µm in size}$ . Gravid proglottids resemble rice grains when dried.	Most common tapeworm in dogs and cats, ribbon-shaped organisms composed of many repeating segments, typically found in the small intestine.	$1$ month
Diroflaria Immitus	No eggs shed; ovoviviparous females release microfilariae ( $L_1$ larvae) directly into the bloodstream.	Size: $15-25 \text{ cm}$ long, found within the right ventricle and pulmonary artery. Lifespan: $5-7$ years in dogs, $2-3$ years in cats.	$6-8$ months
Echinococcus granulosus	Eggs in fecal flotation are indistinguishable from those of Taenia species. They are thick-shelled, embryonated, with a hexacanth embryo.	Small ( $2-9 \text{ mm}$ ) and consist of three proglottids (one immature, one mature, one gravid). Reside in the small intestine.	$50$ days
Echinococcus multilocularis	Eggs measure approximately $38 \times 32 \text{ µm}$ , indistinguishable from Taenia species eggs.	Adult size ranges from $1-5 \text{ mm}$ , residing in the small intestine, typically containing $4-5$ segments.	$40$ days
Eucoleus (Capillaria) aerophila	Eggs are lighter, smaller than T. vulpis, and more broadly barrel-shaped with asymmetric bipolar plugs (often confused with Trichuris (whipworm) eggs).	Range in size from $24-30 \text{ mm}$ and reside in the trachea, bronchi, and bronchioles.	$6-7$ weeks
Giardia spp.	Cyst stage: oval, refractile wall with four nuclei (also includes immature cysts).	Trophozoite (motile feeding stage) is pear-shaped, dorsoventrally flattened, containing four pairs of flagella.	Variable, usually $1$ week for cysts
Nanophyetus salmincola	Gold eggs with operculum, $50-80 \text{ µm by } 30-55 \text{ µm}$ .	Very small, up to $3 \text{ mm}$ in length with one or two deep brown eggs in the uterus, located in the small intestine.	$1$ week
Pearsonema feliscati	Barrel-shaped, colorless, with thick striated shell and bipolar plugs, approx. $65 \times 25 \text{ µm}$ . (Resemble Dioctophyme renale eggs but differ in size and shell pitting).	Ranging from $13-60 \text{ mm}$ and residing in the mucosa of the urinary bladder.	Approx. $2$ months
Pearsonema plica	Barrel-shaped, colorless, with thick striated shell and bipolar plugs, approx. $65 \times 25 \text{ µm}$ . (Resemble Dioctophyme renale eggs but differ in size and shell pitting).	Ranging from $13-60 \text{ mm}$ and residing in the mucosa of the urinary bladder.	Approx. $2$ months
Physaloptera spp.	Thick-walled, smooth, larvated eggs, $42-58 \text{ µm by } 30-42 \text{ µm}$ . Eggs do not float well.	$2-6 \text{ cm}$ , found firmly attached to the stomach or small intestine; suck blood and consume tissue.	$58-83$ days
Spirometra spp.	Operculated, light brown eggs, approximately $60 \times 36 \text{ µm}$ . (Similar to Diphyllobothrium latum eggs).	Adults range approximately $1.5 \text{ m}$ in length and reside in the small intestine.	$10-30$ days
Strongyloides stercoralis	Eggs hatch rapidly (often in utero), so L1 larvae are typically passed in the feces, not eggs.	Adults are found primarily in the small intestine, transparent and relatively small, typically measuring around $2 \text{ mm}$ in length.	Approx. $8-14$ days
Taenia pisiformis	Round to oval eggs, approximately $38 \times 32 \text{ µm}$ with a hexacanth embryo. (Indistinguishable from Echinococcus species eggs and other Taenia species eggs).	Adult can reach up to $200 \text{ cm}$ in length and typically resides in the small intestine.	$2$ months
Taenia taeniaeformis	Eggs measuring $30-40 \text{ µm in size}$ . (Similar to Echinococcus species eggs and other Taenia species eggs).	Can reach lengths of up to $60 \text{ cm}$ and resides in the small intestine.	$5-6$ weeks
Thelazia spp.	No eggs are shed; ovoviviparous females release L1 larvae. These larvae are detected in tears.	Adults range from $7-20 \text{ mm long}$ , appear white and exhibit rapid movement across the eye. Reside in the conjunctival sac, tear ducts, conjunctiva, and under the nictitating membrane and eyelids.	$16-21$ days
Toxascaris leonina	Smooth, thick-walled colorless shell; zygote does not completely fill the eggshell; shell has a wavy internal membrane. Egg size: $75-85 \text{ µm in diameter}$ . (Differs from Toxocara spp. with its smooth shell).	(Not explicitly detailed in terms of adult morphology)	$8-10$ weeks
Toxocara canis	Sub-spherical shape with a thick, rough shell, $75-90 \text{ µm in diameter}$ . Each egg contains one or two cells when freshly passed. (Differs from Toxascaris leonina with its rough shell).	(Not explicitly detailed in terms of adult morphology, but implied to be found in the small intestine after tracheal migration).	$2-4$ weeks
Toxocara cati	Sub-spherical shape with a thick, rough shell, $65-75 \text{ µm}$ . Each egg contains one or two cells when freshly passed. (Differs from Toxascaris leonina with its rough shell).	(Not explicitly detailed in terms of adult morphology, but implied to be found in the small intestine after tracheal migration).	$2-4$ weeks
Toxoplasma gondii	Oocysts are resistant stages shed unsporulated in feces, which sporulate in the environment.	Not an adult worm; protozoan stages are trophozoites (responsible for pathology) and oocysts (transmission).	$1-3$ weeks
Trichomonas spp. (Tritrichomonas blagburni)	No egg stage; trophozoites are shed in feces.	Trophozoites are pear-shaped ( $10-25 \text{ µm long, } 3-15 \text{ µm wide}$ ) and reside in the colon and cecum with four flagella.	Approx. $15$ days
Trichuris vulpis	Thick, yellow-brown, with a symmetric shell and polar plugs (operculum) at both ends, unembryonated when laid. Egg size: $70-90 \text{ µm by } 30-40 \text{ µm}$ . (Resemble Eucoleus aerophila eggs but are larger, darker, and have symmetric polar plugs).	Approximately $75 \text{ mm}$ , lives in the large intestine, burying its whip-like anterior in the intestinal lining to consume blood.	$3$ months

Clinical Signs, Diagnosis, and Treatment Chart

Parasite (Scientific Name)	Clinical Signs	Diagnosis	Treatment
Aelurostrongylus abstrusus	Chronic cough, dyspnea, wheezes.	Baermann technique (L1 larvae with “kinked tail”), fresh fecal samples, bronchoalveolar lavage.	(Not explicitly mentioned in the note, but general anthelmintics would likely be used)
Alaria spp.	(Not explicitly mentioned if any)	Fecal sedimentation or flotation (sugar flotation effective), eggs are oval, light brown, approximately $120 \times 65 \text{ µm}$ .	Praziquantel
Ancylostoma caninum	Anemia, diarrhea, weakness, melena, dermatitis (especially on feet), respiratory disease.	Fecal Floatation (ova $56-75 \text{ µm by } 34-47 \text{ µm}$ , requires fresh feces), Skin Biopsy.	Pyrantel pamoate, Fenbendazole, Moxidectin
Ancylostoma tubaeformae	Anemia, diarrhea, weakness, melena, dermatitis, respiratory disease.	Fecal Floatation (ova slightly longer than A. caninum, requires fresh feces), Skin Biopsy.	Pyrantel pamoate, Fenbendazole, Moxidectin
Baylisascaris procyonis	(Not explicitly detailed for definitive hosts, but conditions include Visceral, Ocular, and CNS Larva Migrans in intermediate/paratenic hosts.)	(Not explicitly detailed for definitive hosts, diagnosis focuses on larvae migration in intermediate/paratenic hosts)	(Control/prevention focuses on environmental measures; treatment in dogs likely similar to other ascarids)
Cystoisospora spp.	Watery diarrhea (sometimes with blood), risk of dehydration and death in young animals.	Standard vial or centrifugal fecal flotation (detect oocysts, commonly round to ellipsoid).	Sulfadimethoxine, ponazuril (compounded)
Dioctophyme renale	Ranging from asymptomatic to hematuria and/or signs of renal dysfunction; dysuria, lumbar pain.	Urine sediment tests (dark brown, barrel-shaped eggs, $65 \times 42 \text{ µm}$ , with opercula and thicker, pitted shells), ultrasound, IV pyelography.	Surgical removal
Diphyllobothrium latum	Common GI signs: vomiting, diarrhea, weight loss.	Detection of chains of segments in vomit or feces; fecal float or sedimentation (operculated, light brown eggs).	Praziquantel
Dipylidium caninum	Scooting, anal irritation, altered appetite, visible proglottids on perineum.	Finding proglottids on pet/feces/environment (appear as rice grains when dry), squash prep of proglottid, PCR or centrifugal flotation (egg packets $35-60 \text{ µm}$ ).	Nitroscanate, Praziquantel, Epsiprantel
Dirofilaria immitis	Dogs: Syncope, sudden death, coughing, vomiting, weight loss, dyspnea, lethargy, anorexia. Cats: Usually associated with arrival of worms in pulmonary vasculature or death of adult worms, sudden death.	Dogs: ELISA test (antigen from female worms over 6 months), Microfilariae Detection (direct blood exam, Buffy coat, Millipore filter, modified Knott test). Cats: Antigen and antibody tests, Chest radiographs, Ultrasound/Echocardiography.	Dogs: Melarsomine dihydrochloride (Adulticide). Cats: Stabilization, prevention (Ivermectin, moxidectin, selamectin, milbemycin oxime).
Echinococcus granulosus	May include irritations around the anus, changes in appetite, and lethargy, often going unnoticed.	Eggs in fecal flotation are indistinguishable from Taenia species eggs; PCR or ELISA.	Praziquantel, Nitroscanate
Echinococcus multilocularis	(Clinical signs often refer to human/intermediate host infection or severe liver damage, not explicitly for definitive host adults).	Proglottids too small to observe; eggs ( $38-32 \text{ µm}$ ) in fecal flotation or PCR.	Praziquantel, Nitroscanate
Eucoleus (Capillaria) aerophila	May be asymptomatic; heavy infestations lead to respiratory symptoms (coughing, nasal discharge, dyspnea) from bronchiolitis and bronchitis.	Detection of ova in sputum or feces via fecal flotation or tracheal wash. Eggs are lighter, smaller than T. vulpis, more broadly barrel-shaped with asymmetric bipolar plugs.	(Not explicitly mentioned in the note, but general anthelmintics would likely be used based on other parasite treatments)
Giardia spp.	Diarrhea (may contain mucus or fat, ranges from acute profuse watery to soft stools).	Fresh fecal smear (warm with saline), centrifugal flotation (zinc sulfate or sugar, cysts difficult to identify), ELISA for fecal antigen (Snap test), PCR testing.	Metronidazole, Fenbendazole
Nanophyetus salmincola	Generally mild gastrointestinal signs: vomiting, diarrhea, lethargy, anorexia. Can transmit Neorickettsia helminthoeca causing Salmon Poisoning Disease (SPD) in dogs, leading to hemorrhagic gastroenteritis.	Fecal sedimentation (gold, operculated eggs $50-80 \text{ µm by } 30-55 \text{ µm}$ ).	Praziquantel, Epsiprantel
Pearsonema feliscati	May be asymptomatic; potential signs of cystitis, dysuria, hematuria, and polyuria.	Urine Sedimentation (amber, barrel-shaped, asymmetric bipolar plugged eggs ( $65 \times 25 \text{ µm}$ )).	Ivermectin, Fenbendazole
Pearsonema plica	May be asymptomatic; potential signs of cystitis, dysuria, hematuria, and polyuria.	Urine Sedimentation (amber, barrel-shaped, asymmetric bipolar plugged eggs ( $65 \times 25 \text{ µm}$ )).	Ivermectin, Fenbendazole
Physaloptera spp.	Vomiting, anorexia, dark, tarry stools (melena).	Direct fecal smear or fecal sediment (fecal float unreliable due to eggs not floating well), look for larvae in vomitus, endoscopy (for adults). Ova: thick-walled, smooth, larvated eggs.	Fenbendazole, Ivermectin
Spirometra spp.	Common symptoms: vomiting, diarrhea, weight loss. Larvae may migrate to subcutaneous regions, eyes, or CNS.	Identifying chains of segments in feces or vomit; eggs ( $60 \times 36 \text{ µm}$ ) in fecal flotation or sedimentation.	Praziquantel
Strongyloides stercoralis	Gastrointestinal signs (severe, often chronic diarrhea, weight loss, malabsorption, vomiting, anorexia), Respiratory signs (coughing, wheezing), Dermatitis (at larval penetration site).	Identifying L1 larvae in fresh fecal samples (eggs hatch rapidly, rarely seen). Baermann technique (effective for motile L1), direct fecal smear (lower sensitivity), fecal culture.	Ivermectin, Fenbendazole, Moxidectin
Taenia pisiformis	Potential intestinal blockage due to heavy burdens.	Proglottids in feces or on pet (resembling rice grains when dried), squash prep of proglottids. Fecal flotation (round to oval eggs $38 \times 32 \text{ µm}$ with hexacanth embryo).	Praziquantel, Epsiprantel, Fenbendazole, Nitroscanate
Taenia taeniaeformis	May include irritation, changes in appetite, or mild diarrhea.	Proglottids in feces or on pet. Crush proglottids between slides to release eggs ( $30-40 \text{ µm in size}$ ).	Praziquantel, Fenbendazole
Thelazia spp.	Lacrimation, conjunctivitis, photophobia, corneal opacity and ulceration.	Detection of ova and larvae through tears.	Local anesthetics for parasite removal with forceps; dewormers.
Toxascaris leonina	(Clinical signs generally similar to other ascarids, e.g., GI upset, poor coat, pot-belly, but not explicitly detailed for this species in the notes)	Fecal Floatation (Egg Size: $75-85 \text{ µm}$ ). Eggs: smooth, thick-walled colorless shell; zygote does not completely fill eggshell; shell has wavy internal membrane.	Pyrantel pamoate, Fenbendazole, Milbemycin oxime, Moxidectin, Nitroscanate
Toxocara canis	Pot-belly appearance, dry, lack-luster hair coat, underweight condition, vomiting, diarrhea, coughing.	Fecal Floatation (T. canis – $75 \text{ µm by } 90 \text{ µm}$ ). Eggs: Sub-spherical shape with thick, rough shell, each egg contains one or two cells when freshly passed.	Pyrantel pamoate, Fenbendazole, Milbemycin oxime, Moxidectin, Nitroscanate
Toxocara cati	Pot-belly appearance, dry, lack-luster hair coat, underweight condition, vomiting, diarrhea, coughing.	Fecal Floatation (T. cati – $65 \text{ µm by } 75 \text{ µm}$ ). Eggs: Sub-spherical shape with thick, rough shell, each egg contains one or two cells when freshly passed.	Pyrantel pamoate, Fenbendazole, Milbemycin oxime, Moxidectin, Nitroscanate
Toxoplasma gondii	Cats: Typically mild; young animals may exhibit fever, anorexia, cough, dyspnea, diarrhea, jaundice, or CNS signs.	Standard vial or centrifugal flotation, PCR, serological tests for antibodies, post-mortem detection of tissue cysts.	Clindamycin, pyrimethamine, trimethoprim, sulfamethoxazole
Trichomonas spp. (Tritrichomonas blagburni)	Chronic diarrhea lasting weeks to years, potentially containing blood or mucus.	Direct fecal smear, fecal culture, PCR testing.	(Not explicitly mentioned in the note, but treatment options exist outside the scope of this note)
Trichuris vulpis	Severe watery diarrhea and anemia in heavy infections; sometimes with hematochezia.	Fecal Floatation (Eggs: thick, yellow-brown, with symmetric shell and polar plugs at both ends, unembryonated when laid. Egg size: $70-90 \text{ µm by } 30-40 \text{ µm}$ ).	Febantel, Moxidectin, Fenbendazole, Milbemycin oxime

Zoonotic Potential Chart

Parasite (Scientific Name)	Zoonotic Potential
Aelurostrongylus abstrusus	No
Alaria spp.	(Not explicitly mentioned, but typically low for humans from domestic animals)
Ancylostoma caninum	Yes
Ancylostoma tubaeformae	Yes
Baylisascaris procyonis	Yes
Cystoisospora spp.	No
Dioctophyme renale	Yes
Diphyllobothrium latum	Yes
Dipylidium caninum	(Less commonly, but possible via flea ingestion)
Dirofilaria immitis	No (not typically for humans from pets)
Echinococcus granulosus	Yes
Echinococcus multilocularis	Yes
Eucoleus (Capillaria) aerophila	(Not explicitly mentioned, but generally considered low)
Giardia spp.	Yes
Nanophyetus salmincola	Accidental hosts (no salmon poisoning in humans)
Pearsonema feliscati	(Not explicitly mentioned, but generally considered low)
Pearsonema plica	(Not explicitly mentioned, but generally considered low)
Physaloptera spp.	(Not explicitly mentioned, but generally considered low)
Spirometra spp.	Yes
Strongyloides stercoralis	Yes

Aelurostrongylus abstrusus Life Cycle

Adult female Aelurostrongylus abstrusus lays eggs in the alveolar ducts and terminal bronchioles.
First-stage larvae (L1) emerge from the hatched eggs in the lungs, are coughed up, swallowed, and subsequently passed through the intestinal tract, exiting the cat's body with the feces.
Terrestrial gastropods (snails or slugs) ingest the L1 larvae present in the cat's feces.
Inside the gastropod, the L1 larvae develop into second-stage (L2) larvae and then into infective third-stage (L3) larvae.
Cats acquire the infection by consuming either an infected intermediate host (snail or slug) directly, or by consuming paratenic hosts (such as rodents, birds, or frogs) that have ingested infected gastropods.
Once ingested by the cat, the L3 larvae penetrate the intestinal mucosa and migrate through the cat's body, primarily via the lymphatic and circulatory systems, aiming for the respiratory system.
The migrating larvae eventually reach the lungs, where they mature into adult worms.

PPP: Approximately 5-6 weeks from ingestion of L3 larvae until L1 larvae appear in the feces.

Alaria spp. Life Cycle

Eggs passed in feces develop into miracidia upon hatching and penetrating a snail (first intermediate host).
Cercaria exit the snail, infect tadpoles (second intermediate host), and develop into mesocercariae.
Mesocercariae adhere and persist through to adulthood in the frog.
Paratenic hosts (e.g., frogs, snakes, and mice) can consume infected tadpoles.
Dogs consume infected tadpoles/frogs or paratenic hosts, leading to maturation in the small intestine.
Mesocercariae may also migrate to mammary glands via lactating queens during transmission to puppies/kittens.

PPP: 5-6 weeks.

Ancylostoma caninum Life Cycle

Infective larvae (L3) are ingested, penetrate the skin, or are transmitted transmammary/transplacentally.
If larvae penetrate the skin, they migrate through the lungs.
Larvae mature in the small intestine to adult worms.
Adult worms lay eggs, which are shed in the feces.
Eggs larvate quickly in the environment, becoming L3.
Ingestion of a paratenic host also leads to infection.

PPP: About 2 weeks.

Ancylostoma tubaeformae Life Cycle

Infection occurs via ingestion of infective larvae (L3), ingestion of a paratenic host, or skin penetration.
Larvae mature primarily in the small intestine to adult worms.
Adult worms lay eggs, which are shed in the feces.

PPP: 2-4 weeks.

Cystoisospora spp. Life Cycle

Ingested sporulated oocysts contain two sporocysts, yielding eight sporozoites.
Sporozoites infect the intestinal epithelium and undergo asexual and sexual reproduction.
Oocysts sporulate in less than a day under ideal conditions (30extto37ext°C30extto37ext°C), becoming infective.

PPP: 1 week.

Dioctophyme renale Life Cycle

Infected definitive hosts produce eggs that are passed in urine.
Eggs are ingested by an annelid (intermediate host) and develop from L1 to L3.
Definitive hosts get infected by consuming L3 within the annelid or paratenic hosts (frogs, fish, crayfish).
L3-stage larvae penetrate the stomach, migrate to the abdominal cavity, and settle in the right kidney.

PPP: 5 months.

Diphyllobothrium latum Life Cycle

Eggs are shed in feces.
Eggs must embryonate in water before being ingested by a copepod (first intermediate host).
Developed larvae are later ingested by fish (second intermediate host).
Definitive host consumes the fish, maturing the larva into a tapeworm which attaches within the intestines to develop proglottids.
Eggs are released from the proglottid and expelled in feces.

PPP: 4-6 weeks.

Dipylidium caninum Life Cycle

Flea larvae ingest eggs from proglottids.
Eggs develop into immature larvae (metacestode) in the flea.
Dog or cat ingests a flea containing the immature larva.
Immature larva releases protoscolex upon ingestion, attaches to the small intestine, and develops into an adult with proglottids.
Gravid proglottids detach and are passed within feces.

PPP: 1 month.

Dirofilaria immitis Life Cycle

Mosquito ingests microfilariae (L1 stage larvae) circulating in the dog's bloodstream when feeding on an infected dog.
Within the mosquito's Malpighian tubules, the microfilariae (L1) develop into L2 larvae and then into infective L3 larvae over approximately 10-14 days. Ideal conditions are around 27ext°C27ext°C (80ext°F80ext°F).
When the infected mosquito subsequently feeds on another dog, the infective L3 larvae are injected into the subcutaneous tissues of the new host.
Within 1-2 days (approximately 48 hours) post-infection, the L3 larvae molt to the L4 stage within the dog's subcutaneous tissues.
The L4 larvae continue to develop and migrate through the subcutaneous and muscle tissues, maturing into young adults over a period of 50-70 days.
These young adults then migrate via the venous circulation to the right ventricle of the heart and the pulmonary arteries, arriving approximately 70-120 days post-infection.
Upon arrival in the heart and pulmonary arteries, the young adults typically measure about 2-4 cm long and rapidly grow to their adult size of 15-25 cm.
Mature female worms in the pulmonary arteries begin to release new microfilariae (L1) directly into the bloodstream of the dog.

PPP: Commonly lasts 6-8 months.

Echinococcus granulosus Life Cycle

Eggs are shed in the feces of the definitive host (dog).
Intermediate host (e.g., sheep) ingests the eggs while grazing.
The embryos hatch and involve larval travel to various tissues (liver, lungs, brain) forming hydatid cysts.
Dogs ingest cysts from intermediate hosts.
Cysts develop into adult tapeworms in canids.

PPP: 50 days.

Echinococcus multilocularis Life Cycle

In Intermediate Hosts

Post-ingestion of thick-shelled, embryonated eggs by a small rodent, the hexacanth embryo hatches in the small intestine.
The larval tapeworm then penetrates the intestinal wall, gaining access to the bloodstream.
The larva travels via the bloodstream, primarily to the liver, initiating development, and can disseminate to other vital organs, forming alveolar hydatid cysts.

In Definitive Hosts

A dog or other wild canid ingests the small rodent intermediate host infected with alveolar hydatid cysts.
Once ingested, protoscolices present within the hydatid cysts are released in the definitive host's small intestine.
Protoscolices evaginate, firmly attach to the intestinal lining, and rapidly develop into adult tapeworms, forming new proglottids.
Less than two months post-infection, gravid proglottids containing many infective eggs detach from the strobila and are shed in feces.

PPP: 40 days.

Eucoleus (Capillaria) aerophila Life Cycle

Eggs in sputum or feces are expelled (oral-fecal route).
Infection occurs through ingestion of infective ova or paratenic hosts, such as infected earthworms.
Larvae from ingested eggs hatch in the small intestine and penetrate the mucosa.
Larvae then migrate to the lungs via the bloodstream.

PPP: 6-7 weeks.

Giardia spp. Life Cycle

Cysts are ingested through contaminated water or feces.
Cysts release trophozoites in the small intestine, which attach to the intestinal wall.
Trophozoites divide by binary fission while some encyst and are excreted in feces.
Cysts can persist in environments for extended periods.

PPP: Variable but usually 1 week for cysts.

Nanophyetus salmincola Life Cycle

Definitive host (dog) excretes eggs in feces, which mature in water into miracidia.
Miracidia penetrate the snail skin (first intermediate host) and develop into cercaria.
Cercaria emerge from the snail and infect fish (second intermediate host—mainly salmon, sturgeon, or trout), leading to the metacercaria stage in the skeletal muscles.
When raw fish is consumed, the parasite matures into an adult in the small intestine, where eggs are laid and passed with feces.

PPP: 1 week.

Pearsonema plica & Pearsonema feliscati Life Cycle

Eggs are shed in the urine of the definitive host (dogs or cats) into the external environment.
Outside, under suitable conditions, eggs embryonate and first-stage larvae (L1) develop within them over approximately 30 days.
Embryonated eggs are ingested by an obligate intermediate host (an annelid).
Within the earthworm's alimentary canal, L1 larvae hatch, penetrate the intestinal wall, and migrate to the coelomic cavity of the earthworm. They develop into infective third-stage (L3) larvae, typically over 2-3 weeks.
The definitive host (dog or cat) becomes infected by ingesting an earthworm containing these infective L3 larvae or via small rodents, birds, or frogs that have previously ingested infected earthworms.
Once ingested by the definitive host, the L3 larvae penetrate the intestinal wall and migrate via the lymphatic and circulatory systems to the urinary bladder.
Upon reaching the urinary bladder, the L3 larvae mature into adult male and female worms, embedding themselves in the urinary bladder mucosa, mating, and laying eggs.

PPP: Roughly 2 months.

Physaloptera spp. Life Cycle

Intermediate host (crickets, cockroaches, beetles) ingests the parasiteʼs eggs from the feces of the definitive host.
Eggs hatch in the gut of the intermediate host and develop into the third-stage infective larva.
Infection of the canine or feline definitive host follows ingestion of an infected intermediate host. Once in the definitive host, the larvae mature into adults which are found in the stomach or small intestine.

PPP: 58-83 days.

Spirometra spp. Life Cycle

Eggs are shed in feces.
Eggs must embryonate in water before being ingested by a copepod (first intermediate host).
Developed larvae are later ingested by a second intermediate host (various non-fish vertebrates like reptiles, mammals, birds, amphibians; humans can act as paratenic hosts).
Definitive host consumes the second intermediate host, maturing the larva into a tapeworm which attaches within the intestines to develop proglottids.
Eggs are released from the proglottid and expelled in feces.

PPP: 10 to 30 days.

Strongyloides stercoralis Life Cycle

Ova hatch in the intestine, and L1 larvae are then passed in the feces.
Once L3 larvae infect a host (via skin penetration or ingestion), they migrate through the body, often involving a tracheal migration route:
- Larvae enter the bloodstream, travel to the lungs.
- From the lungs, they move up the airway, are coughed up and then swallowed.
- They finally reach the gastrointestinal (GI) tract where they mature into adult worms.
Autoinfection: L1 larvae within the host can develop into L3 larvae, penetrate the intestinal wall or perianal skin, and re-enter the bloodstream without exiting the host.
Transmission via milk from an infected dam to offspring is also possible.

PPP: Approximately 8-14 days.

Taenia pisiformis Life Cycle

Rabbit (intermediate host) ingests tapeworm eggs.
Embryo develops into an immature larva (metacestode) in the rabbit.
Dog (definitive host) eats the rabbit which contains the immature larva.
Larva releases protoscolex that attaches to the small intestine lining and grows into an adult, producing proglottids.
Gravid proglottids detach and are passed in feces.

PPP: 2 months.

Taenia taeniaeformis Life Cycle

Rodent (intermediate host) ingests tapeworm eggs.
Embryo develops into an immature larva (metacestode) in the rodent.
Cat (definitive host) eats the rodent which contains the immature larva.
Larva releases protoscolex that attaches to the small intestine lining and grows into an adult, producing proglottids.
Gravid proglottids detach and are passed in feces.

PPP: 5-6 weeks.

Thelazia spp. Life Cycle

Adult worms reside in the conjunctival sac of the definitive host.
Ovoviviparous females release L1 larvae.
L1 larvae are ingested by the intermediate host (Drosophila flies, fruit flies) during feeding on tear fluid and lacrimal secretions.
Larvae develop to L3 in the intermediate host and migrate to the fly's mouthparts.
Upon the fly feeding on a new definitive host, the larvae invade the conjunctival sac and develop into adults.

PPP: 16-21 days.

Toxascaris leonina Life Cycle

Eggs are shed in feces and become infective (larvated) in the environment, usually in about 1 week.
Definitive host (dog or cat) ingests infective eggs or a paratenic host (e.g., rodents) containing larvae.
Larvae develop in the host's small intestine and mature into adults.
Adults lay eggs, which are shed in feces.

PPP: 8 to 10 weeks.

Toxocara canis Life Cycle

The parasite enters the body via ingestion of infective eggs, ingestion of a paratenic host (e.g., rodent), transmammary, or transplacentally.
The parasite migrates through various organs to the lungs, and into the trachea.
From the trachea, the larvae are coughed up and swallowed, then travel to the small intestines where they mature into adults.
Eggs are shed in the feces, and the cycle begins anew.

Egg Larvation: Egg larvates (L3) in 3-4 weeks, temperature dependent.
PPP: 2-4 weeks.

Toxocara cati Life Cycle

The parasite enters the body via ingestion of infective eggs, ingestion of paratenic hosts (e.g., rodent), or transmammary from the queen.
The parasite migrates through various organs to the lungs and into the trachea.
From the trachea, larvae are coughed up, swallowed, and travel to the small intestine to mature into adults.
Eggs are shed in the feces, and the cycle begins anew.

PPP: 2-4 weeks.

Toxoplasma gondii Life Cycle

Cats (definitive host) shed unsporulated oocysts that sporulate in the environment.
Pathway 1 (Minority): Cats ingest sporulated oocysts, undergo reproduction in the intestines, and excrete oocysts again.
Pathway 2 (Majority): Intermediate Hosts ingest oocysts, leading to the development of trophozoites that multiply in tissues; can also infect through the ingestion of tissue cysts or spores.

PPP: 1-3 weeks.

Trichomonas spp. (Tritrichomonas blagburni) Transmission Route (as per notes)

Shed trophozoites in feces; ingestion occurs during grooming or through contaminated food or water.

Trichuris vulpis Life Cycle

Eggs are shed in feces and larvate in the environment for approximately 10 days to become infective ova.
Definitive host ingests infective ova.
Larvated eggs hatch in the intestinal lumen, releasing larvae.
Larvae mature in the large intestine, burying their whip-like anterior in the intestinal lining.
Adult