Veterinary Science- Parasitology

Notes from Parasitology presentation. Made for New Horizons Veterinary Science class.

Parasitology

the study of parasites

Parasite

a living organism that obtains nourishment from another living thing that does not benefit from the relationship

Host

the organism that provides the parasite with nutrients/place to develop

Intermediate Host

an organism that supports the immature/nonreproductive forms of a parasite

Ova

Egg

Larva

an immature form of a parasite, often a worm-like organism

Vector

an organism that spreads a disease-causing pathogen

Ectoparasites

parasites that live outside of the body

Endoparasites

parasites that live within the body

Classifications of Parasites

• Protozoa/Protozoans

• Helminths

• Arthropods

Protozoa/Protozoans

single celled organism, some of which can be parasitic whereas others can live freely without a host

Helminths

broad term for parasitic worms

Types of Helminths

• Nematode

• Trematode

• Cestode

Characteristics of Nematodes

round, long parasitic worms; non-segmented

Characteristics of Trematodes

flat, leaf-like worms

Characteristics of Cestodes

flat, segmented worms

What type of helminth (parasitic worm) is this?

Nematode (Roundworm)

What type of helminth (parasitic worm) is this?

Trematode (Nanophyetus salmincola)

What type of helminth (parasitic worm) is this?

Cestode (Tapeworm)

Arthopods

ticks, lice, fleas, mites

Can you look at a patient and determine if they are battling parasitism?

NO

There aren’t always physical signs of parasitism, and some parasites can cause minimal signs that aren’t even recognizable. Additionally, most live within the host and are microscopic.

Can parasites impact the pet owner?

YES

• Can be zoonotic

• Can act as vectors for human diseases

• Causes significant illness in pets

• Create a financial burden

Potentially Zoonotic Parasites (Name 3)

• Roundworms

• Giardia

• Ticks (vectors of Lyme disease & Rocky Mountain Spotted Fever)

• Fleas

• Certain tapeworms

• Toxoplasma gondii

• Roundworms

• Hookworms

How can you prevent parasitism?

• Flea/Tick prevention

• Heartworm prevention/Monthly Gastrointestinal parasite prevention

• Basic hygiene (picking up feces in the yard)

Why is it important to pick up feces right away?

Picking up feces is an important step in regulating the environment and preventing parasitism. Many parasite eggs will be passed on through feces and will sporulate (become infective) after being in the environment for a while. It’s imperative to pick feces up as soon as you see it to prevent parasites from becoming infective and your dog from consuming it.

Examples of Protozoans

• Coccidia

• Giardia

• Toxoplasmosis

Coccidia

gastrointestinal parasite that can cause diarrhea, weight loss, dehydration; there are many types of coccidia, and they tend to be species specific

Coccidia Life Cycle

1. Eggs (oocysts) are deposited into environment via feces and sporulate

2. Once consumed, oocyst ruptures in the GI tract and burrow into intestinal lining

3. Develops into different phases while in intestinal lining —> damaged intestinal cells (origin of clinical signs)

4. Reproduction occurs inside lining and eggs are released

Coccidia Diagnosis & Treatment

Diagnosis: Fecal floatation test

Treatment: Animals w/o treatment and otherwise healthy may not require treatment. Animals w/ clinical signs and + fecal test should be treated (Sulfa drugs).

ENVIRONMENTAL CONTROL IS CRUCIAL TO PREVENT REINFECTION

Giardia

gastrointestinal parasite common in dogs that comes in various, species specific “assemblages”; can cause diarrhea and weight loss

Giardia Life Cycle

1. Trophozoite form of giardia lives in intestines and is mobile due to flagella

2. Attaches to intestinal wall and multiplies via binary fission

3. Encysted form will pass into environment via feces and remain viable in supportive environments

4. Cyst is infective and leads to infection once consumed

Giardia Diagnosis & Treatment

Diagnosis: Fecal floatation test, Antigen test

Treatment: Treatment may not be needed. Should be considered if living with an immunocompromised individual

Toxoplasma gondii

causative agent of toxoplasmosis; rarely can cause fever, lethargy, loss of appetite and pneumonia in cats or jaundice depending on where it encysts

Toxoplasmosis

Zoonotic parasite found in cat feces that can cause miscarriage in humans

Toxoplasma gondii Life Cycle

1. Oocysts passed in feces, becomes infective after 1-5 days

   • If picked up by cat, life cycle is complete

   • If picked up by another animal, oocyst will continue to develop and encyst in tissue ↓

2. Cats can become infected if they ingest an animal w/ encysted toxoplasma

3. Toxoplasma will break down cyst and reproduce in GI cells

4. New forms of toxoplasma produced and travel to other tissues in body

Toxoplasma gondii Diagnosis & Treatment

Diagnosis: Can be challenging. Blood test can identify antibodies, but this could mean EXPOSURE and not actual illness. Fecal test is unreliable as Toxoplasma oocyst looks similar to other parasites. May need tissue biopsies

Treatment: Antibiotics

Roundworms (Toxocara spp.)

gastrointestinal parasites once mature; immature forms travel through body (i.e. lungs and liver) and cause clinical signs; transmitted via ingestion (of eggs or paranteric host), in-utero, or infected milk; extremely common, should be assumed all pups/kits have them and should be routinely dewormed

Roundworm egg

Roundworm Symptoms

• vomiting/diarrhea

• failure to gain weight

• poor coat quality

• pot-bellied appearance in puppies/kittens

Roundworm Diagnosis & Treatment

Diagnosis: Fecal test identifies egg

Treatment: Supportive care, repeated deworming, appropriate medication (”strongid,” monthly heartworm prevention)

Roundworms in Humans

Zoonotic potential; leads to larval migrands which are extremely uncomfortable which can lead to blindness in children; hygiene is important to teach children to prevent accidental contamination

Hookworms (Ancylostoma spp.)

gastrointestinal parasite that sucks blood by latching onto intestinal wall with their 6 teeth; zoonotic and can be transmitted via in-utero, infected milk, contact with infective larva, ingestion (infected animal or environment)

Hookworm egg

Hookworm Symptoms

• diarrhea

• pale mucous membranes

• lethargy

• weakness

• in severe cases, anemia

• can also cause cutaneous larval migrans

Hookworm Diagnosis & Treatment

Diagnosis: Fecal float identifies egg

Treatment: Routine heartworm prevention, dewormers (only effective to parasites within intestines)

Whipworms (Trichuris spp.)

gastrointestinal parasite that sucks in the cecum; infected barely show signs unless burden is high; potentially zoonotic

Whipworm egg

Whipworm Diagnosis & Treatment

Diagnosis: can be difficult; whipworms have intermittent reproduction cycle so sometimes eggs are not detectable

Treatment: Strenuous deworming

Heartworms

serious, preventable disease that can affect dogs and cats; spread via mosquitos; worms live in pulmonary artery and can spread to other chambers, drastically changing heart function leading to heart failure and death

Heartworm Life Cycle

1. Adult worms give birth to microfilaria (L1) while living in pulmonary artery (live birth)

2. L1 is picked up by feeding mosquito

3. Develops into L2 and L3 stage within mosquito

4. Mosquito feeds on another host, deposits L3 in spitball besides bite which then enters wound

   1. Must be humid within environment

5. Develops into L4 where it lives in skin for 3 months until it matures into L5

6. L5 goes into circulation and homes in pulmonary artery

Heartworm Diagnosis & Treatment

Diagnosis: “Snap” Test identifies female adult heartworm antigen; Knotts Test identifies microfilaria; takes at least 6 months from time of infection for diagnosis due to life cycle; No test can detect L3, L4, L5

Treatment: Need to kill parasite of heartworm 1st (WOLBACHIA via Doxycycline and Prednisone). To kill actual heartworm, needs 3 injections of Melasrsomine dihydrochloride DEEP into epaxial muscles of the back (very uncomfortable). Expensive, dangerous, and requires exercise restricted. Dead worms can get lodged and cause EMBOLI causing respiratory emergencies

Nanophyteus salmincola

fluke that carries ricketseial bacteria that causes salmon poisoning; spread via ingestion of raw fish in Pacific Northwest that harbor fluke

Nanophyetus salmincola Symptoms

• Rickettsia will travel through body to infect liver, lungs, lymphoid tissues, and brain

• nausea

• fever

• lymph node enlargement

• seizures

• difficulty breathing

• vomitig

• bloody diarrhea

• weight loss

• nasal/ocular discharge

Nanophyetus salmincola Diagnosis & Treatment

Diagnosis: History and location of patient; Identifying fluke eggs in feces (fecal float)

Treatment: Supportive care, antidiarrheals, anti-vomit, antibiotics, blood transfusions, medications to kill fluke

Large portion of dogs will die within 7-10 days of clinical signs if not treated. If treated - prognosis is good!

There are _____ types of tapeworms. _____ is harmful to humans and has zoonotic potential.

MANY; Echinococcus multilocularis

Diplylidium caninum

specific tapeworm that infects dogs through ingestion of infected flea; does little harm to host; can also be zoonotic but humans must ingest infected flea

Proglottids

Tapeworm eggs that are deposited into environment; have digestive and reproductive systems

Dipylidium caninum Diagnosis & Treatment

Diagnosis: visualizing “grains of rice” (proglottids) around rectum, on feces, or in environment; pet doesn’t have to have fleas to have tapeworms

Treatment: Oral dewormer to target tapeworms, controlling fleas

Taenia spp.

species of tapeworms that infects animals through ingestion of raw meat; lifecycle similar to dipylidium (lives in intestines, grows proglottids), ingested by intermediate host and travels to liver and encysts in abdomen; has zoonotic potential

Taenia spp. Diagnosis & Treatment

Diagnosis: Visualizing proglottids

Treatment: Administering dewormer

Ectoparasites

• Ticks

• Fleas

• Mites

• Lice

Types of Ticks

15 types in North America. Most common concern are:

• American Dog Tick

• Lonestar Tick

• Deer Tick

• Browndog Tick

Tick Life Cycle

1. Eggs- fertilized female lays eggs

2. Larvae- Eggs hatch into 6-legged larvae

3. Nymph- Larvae molt into 8-legged nymph in environment

4. Adult- Nymph molts into 8-legged adult

Ticks

bites and attaches to skin and sucks blood; transfers diseases, some of which spread quickly and others require more time; attached ticks should be swiftly removed

Diseases Transmitted via Ticks

• Rocky Mountain Spotted Fever

• Anaplasma*

• Ehrlichia*

• Lyme*

*regularly screened for in Snap Tests

Tick Removal

1. Don’t remove w/ fingers

2. Use tweezers, grasp tick close to skin

3. Pull straight up, do not twist or squeeze

4. Once removed, clean skin w/ alcohol or soap and water

5. Don’t squish tick- submerge it, flush, or seal it

Monitoring Tick Bites

Bite will leave behind small, itchy bite wound which should be closely monitored for infection; not all dogs with tick borne disease will show signs, if dog has been bit in recent history and is showing signs, see a vet ASAP

Snap 4Dx

tests dog’s blood simple in-office test requires only a few drops of your dog’s blood, and can within minutes diagnose Lyme disease, ehrlichiosis, and anaplasmosis.

Serology

Serum, which is the liquid part of your dog’s blood, is sent to a veterinary diagnostic lab and tested for antibodies against tick-borne diseases.

Blood Smear

A drop of blood is spread on a glass slide, stained, and viewed under a microscope to check for signs of infection or infectious organisms.

Polymerase Chain Reaction (PCR)

A blood, joint fluid, or lymph node sample is sent to a lab for testing to diagnose tick-borne diseases.

Blood Work

check your dog’s red and white blood cells, platelets, and internal organ function. While this test alone does not diagnose tick-borne diseases, it’s helpful to assess your dog’s overall health. 

Urinalysis

Urine testing can help assess your dog’s kidney function and can identify protein in the urine, which may indicate a tick-borne disease.

Tick Borne Disease Treatment

• antibiotics (doxycycline)

• NSAIDs/Steroids reduce inflammation and discomfort

Important to regularly check dog for visible parasites to prevent disease, remove ticks, utilize preventative medications year round

Fleas

small, common, external arthropods that cause itchiness, skin irritation, secondary infections, and transmit diseases; zoonotic

Flea Life Cycle

1. Egg- fall into environment; 40 a day

2. Larvae- hatch and move to shady environment to make cocoon

3. Pupae- lives in cocoon; hatches due to vibration, light, or carbon dioxide

4. Flea- only adult stage lives on host; doesn’t

Signs of Fleas

• itchy

• red bumps

• overgrooming

• redness of skin

• hair loss

• severe cases can cause anemia

• can be vectors of disease

  • tapeworms, bubonic plague, bartonella

Flea Diagnosis & Treatment

Diagnosis: Clinical signs, visualization of flea/flea dirt, lack of preventatives, location of irritation

Treatment: may be needed to address secondary problems, treat flea itself via preventatives, environmental cleaning, vacuuming, washing bedding

Flea/Tick preventions could be used on other animals (Off Label Use)

Types of Mites

• Walking Dandruff

• Scabies

• Demodectic Mange

• Ear Mites

Sarcoptic Mange (Scabies)

contagious parasite that causes intense itch; zoonotic though dogs are their favorite; transmitted via contact

Scabies Life Cycle

Completed entirely on dog

1. Females burrow tunnels in the skin and lay eggs

2. Hatch after a few days and larva also burrow tunnels

3. Molt 2x as nymphs

4. Adults mate in skin

Scabies Symptoms

• itchy

• inflamed skin

• hair loss

• inflammation

• darkening of skin

• oozing sores

Scabies Diagnosis & Treatment

Diagnosis: Skin scraping (scraping skin with dull blade and evaluating skin cells)

Treatment: Treatable but takes a long time; heartworm prevention may help

Demodectic Mange (Demodex spp.)

normally found in skin within hair follicle; disease occurs with overabundance as result of immune compromise; transmits via direct contact

Signs of Demodex

• patchy hair loss

• generally not itchy

• localized or generalized

• common in dogs less than 6 months

Demodex Diagnosis & Treatment

Diagnosis: Deep skin scraping

Treatment: No specific product though flea/tick products work extralabel, treat underlying conditions, may resolve on own

Cheyletiella spp. (Walking Dandruff)

non-burrowing mites that live on skin; mobile; contagious via direct contact or fleas, lice, and flies; causes flaky dandruff; low zoonotic chance

Otodectes cynotis (Ear Mites)

mite that lives within ear; more common in cats than dogs; low zoonotic chance; lead to ear infections

Ear Mites Diagnosis & Treatment

Diagnosis: Ear swab evaluated under microscope; can cause neurologic damage if too far deep

Treatment: Heartworm preventatives, cleaning out debris

Lice

flat, wingless insect similar in size to flea; not zoonotic; two types:

• Biting/chewing eat tissue debris

• Sucking lice feed on blood

Cause scratching, excessive biting, restlessness

Lice Diagnosis & Treatment

Diagnosis: visualizing lice, confirming under microscope

Treatment: flea/tick products