Parasitology - Intro

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Protozoan Parasites:

single celled organisms

microscopic

usually multiply within host

can have direct or indirect life cycle

Acute infection - parasite numbers increase rapidly (younger animals, lactating and pregnant)

Chronic infection - parasite numbers increase but controlled by host immune response, parasites not cleared 100%

Leishmania

Hosts: man, dog + wild animals

Intermediate host: sandfly

> increase in UK cases due to pet travel

Symptoms: Skin ulcers, hair loss and eczema

Metazoan parasites - Helminths

1. Roundworms (nematodes)

2. Platyhelminths (flatworms)

- trematodes (flukes)

- cestodes (tapeworms)

*also include ectoparasites e.g. ticks + fleas

multicellular

adult stages can be cm in length

most don't replicate within the host

can have direct or indirect lifecycle

Nematodes:

Develop from egg, to larvae, to adult stage

Toxocara canis - dogs (direct)

Haemonchus contortus - sheep (direct)

Flatworms

Flukes and tapeworms

Fasciola hepatica (liver fluke) - sheep/cattle (snail as vector)

Schistosoma bovis - cattle (aquatic snail as vector)

Echinococcus granulosus - dog tapeworm

Taenia solium - pig tapeworm

*parasites can be used therapeutically for autoimmune disease and allergies

(Nematode Tricuris suis) can be used as treatment for Crohn's disease, Type 1 diabetes, MS etc. as can alleviate symptoms by decreasing immune system activity (treg cells))