Parasitology

Zoonosis definition?

The process whereby an infectious disease is transmitted between speicies, either4 directly or via a vector, from animals to humans.

What can cause a zoonotic disease? (4)

Viruses, Bacteria, Parasites, Fungi

Definitive host definition?

A host in which the parasite reaches maturity and, if possible, reproduces sexually

Intermediate host definition?

a host that harbours the parasite only for a short transition period, during which (usually) some developmental stage is completed

Paratenic host definition?

similar to an intermediate host. A host that harbours the parasite only for a short transition period, however is not necessary for the parasite’s development cycle to progress

incidental (Dead-end) host definition

An intermediate host that generally does not allow transmission to the definitive host, thereby preventing the parasite from completing its development.

Angiostrongylus cantonesis causes what disease?

Angistrongyliasis

What is the definitive host for Angiostrongylus cantonesis

Rats

What type of hosts are humans for Angiostrongylus cantonesis?

Incidental/Dead End host

What are the intermediate host for Angiostrongylus cantonesis

Snails and Slugs

What is the incubation period for Angiostrongylus cantonesis?

1 day to >6 weeks (averaging 1 to 3 weeks)

How long does the illness caused by Angiostrongylus cantonesis last?

2-8 weeks (but can be longer)

What are the clinical presentation of the illness cause by Angiostrongylus cantonesis? (2)

Eosinophilic Meningitis and Ocular angiostrongyliasis

List two types of endoparasites

Helminths (worms) and Protozoa

What are two types of Helminths (worms)?

platyhelminths (flatworms) and nematodes (roundworms)
- these are the Phylum of the parasites

What are two types of platyhelminths (flatworms)

Trematodes (flukes) and cestodes (tapeworms)
- these are the Class of the parasite

How are protozoa categorised?

According to their mode of movement

Name 4 types of Protozoa

Amoebas, Flagellates, Cilliates, and Sporozoa

What do Amoebas use to move?

Pseudopodia

What do Flagellates use to move?

Flagella

What do Cilliates use to move?

Cillia

What do Sporozoa use to move?

Nothing, Sporozoa don’t move.

What are the two largest categories for parasites?

Endoparasites, and Ectoparasites

What is one category of ectoparasite?

Arthropods.

What are some examples of Arthropods? (3)

Lice, Ticks, Mites

What are some geographical factors that affect the distribution of parasites? (5)

• Climate

• Soil type (Sand, line)

• Coprozoic organisms (beetles, earthworms, slugs)

• Surface water

• Vegetation

What are some socioeconomic factors that can affect the distribution of parasites? (8)

• Housing

• Copophagic animals

• Urbanisation

• Economic Activities

• Domestication of animals

• Migration

• Wars

• Tourism

What 3 things does a parasite need to become established in vivo?

1. Ecological specificity

2. Ethological Specificity

3. Physiological specificity

What does Ecological specificity mean?

The external environment must allow for the presence and survival of the infective form of the parasite.

What does Ethological specificity mean?

Human behaviour in that environment must enable access of parasitic stage to human tissue (eg. consuming contaminated food or drink)

What does physiological specificity mean?

The potential host’s internal environment must be suitable for invasion and development of parasites.

What is biotic potential?

The ability of an organism to increase its potential to cause disease through increased numbers.

What causes eosinophilic meningitis/meningoencephalitis in Angistrongyliasis?

The presence of migrating larvae in the brain and the consequent host reactions.

What are the symptoms of Angistrongyliasis in adults? (5)

• Severe headaches (95%)

• Nausea (28%)

• Vomiting (38%)

• Neck stiffness (46%)

• Seizures and neurological abnormalities (44%)

What are the symptoms of Angistrongyliasis in children? (3)

• Nausea and vomiting (82%)

• Fever (80%)

• Abdominal pain (34%)

What is this?

genus

Angiostrongylus

What can be used to help diagnose Angiostrongylus? (5)

• Detecting Angiostrongylus cantonesis

• History of travel to where the parasite is found and ingestion of raw or undercooked hosts (snails, slugs, or frogs, freshwater shrimps, land crabs) in those areas

• Eosinophilia in peripheral blood

• Eosinophilia in Cerebrospinal Fluid

• Serological tests

What is this?
Genus

Angiostrongylus

What parasite might this patient have?

Angiostrongylus

Rhabditiform Larva definition

Early developmental larval stages (first and second) of soil-borne nematodes such as Necator, Ancylostoma, and Strongyloides

Filariform Larva definition

infective third-stage larva of the hookworm, Ascaris, and other nematodes with penetrating larvae or with larvae that migrate through the body to reach the intestine.

What is this?

Hookworm

What is this?

Hookworm

What are the most common manifestation of zoonotic infection with hookworm?

Cutaneous Larva Migrans, aka ground itch

What serologic tests can you uses for Zoonotic hookworm infections?

None. There are no serologic tests for Zoonotic hookworm infections.

What causes Toxocariasis?
Phylum

Nematode (roundworm) sp.

What causes Toxocariasis?

Genus, species (3)

Toxocara canis (from dogs)
Toxocara cati (from cats)

Toxascaris leonina

What is this?

Genus, species

Toxocara canis

What would this be if you switched the dogs for cats?
Genus, species

Toxocara cati

What are the two main clinical presentations for Toxocariasis?

Visceral larva migrans (VLM) and Ocular larva migrans (OLM)

What are the symptoms of Visceral larva migrans?

Fever, anorexia, weight loss, cough, wheezing, rashes, hepatosplenomegaly, and hypereosinophilia. Rarely there can be death due to severe cardiac, pulmonary, or neurological involvement

Ocular larva migrans usually occurs in what age group?

older children or young adults

Visceral larva migrans usually occurs in what age group?

Preschool childrean

What results from Ocualr larva migrans?

Ophthalmologic lesions, typically only in one eye that can cause irreversible vision loss

What is the only means of confirming a clinical diagnosis of visceral larva migrans, ocular larva migrans, and covert toxocariasis?

Antibody detection tests. The currently recommended one being enzyme immunoassay

What causes Toxoplasmosis?
Genus, species

Toxoplasma gondii

What is this?
Genus, species

Toxoplasma gondii

What is the definitive host for Zoonotic Hookworms?

Cats and Dogs

What is the definitive host for Toxocara?

Dogs with Toxocara canis
Cats with Toxocara cati

What is the definitive host for Toxoplasma gondii?

Cats

What routes usually infect humans with Toxoplasma gondii? (5)

• Eating undercooked meat from infected animals

• Consuming food or water infected with cat faeces

• Contaminated environmental samples

• Blood or organ transfusion

• Transcendentally from mother to child

Where do the cysts caused by toxoplasmosis commonly form in human hosts? (4)

• Skeletal Muscle

• Myocardium

• Brain

• Eyes

What is the primary diagnostic method for Toxoplasmosis?

Detection of Toxoplasma-specific antibodies

What is this?
Genus, species

Toxoplasma gondii

What typically causes Fascioliasis?
Genus, species

Fasciola hepatica
or occasionally Fasciola gigantica

What is this?
Genus?

Fasciola sp.

What causes Echinococcosis (Hydatid disease)?
Genus?

Echinococcocus sp.

What is this?
Genus

Echinococcus sp

What is the definitive host for Echinococcus sp.?

Dogs

What is this?
Genus

Echinicoccus

What is Organism A? Genus, species
Organism A infections remain silent for years before the enlarging cysts cause symptoms in the affected organs

• Hepatic involvement can result in abdominal pain, a mass in the hepatic area, and biliary duct obstruction

• Pulmonary involvement can produce chest pain, cough, and haemoptysis.

• Rupture of the cysts can produce fever, urticaria, eosiophilia and anaphylactic shock, as well as cyst dissemination

• In addition to the liver and lungs, other organs (brain, bone, heart) can also be involved, with resulting symptoms

Echinococcus granulosus

What is Organism B? Genus, species
Organism B affects the liver as a slow growing destructive cystic mass, with abdominal pain, biliary obstruction, and occasionally metastatic lesions into the lung and brain

Echinococcus multilocularis

What is Organism C? Genus, species
Organism C affects mainly the liver, where it acts as a slow growing mass; secondary cystic development is common.

Echinococcus vogeli

What causes Dirofilarasis?
Genus

Dirofilaria sp.

What 3 Dirofilaria species are most commonly seen in humans?

Dirofilaria repens, Dirofilaria tenuis, Dirofilaria immitis

Sort the following into either pulmonary dirofilariasis or subcutaneous dirofilariasis:

• D. repens,

• D. tenuis,

• D. immitis

Pulmonary dirofilariasis: D. immitis

Subcutaneous dirofilariasis: D. repens, D. tenuis

If you saw a coin lesion on a chest radiography what organism might you suspect?
Genus, species

Dirofilaria immitis

What is this?
Genus, species

Dirofilaria immitis

What is the definitive host for Dirofilaria immitis?

Dogs