Veterinary Protozoology

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Parasites are dependent on host for completion of part or whole life cycle

Endoparasites = helminths + protozoa

Ectoparasites = insects + arachnids (live on or within the surface layers of the skin

Plasmodium (malaria): fever, anaemia + death

Trypanosomes: sleeping sickness

Leishmania: cutaneous, mucocutaneous, visceral

Trichomonas: infertility in cattle

Why are protozoan parasites important?:

economic burden: livestock industry

health and welfare: livestock and pets

zoonotic infections: owners and public health

Parasites:

- become masters of immune evasion

- evade and manipulate immune response

- manipulate the behaviour of the host to maximise chance of spread

Eimeria in poultry:

intracellular parasite

economically significant

causes significant problems in poultry production systems

control methodology reduced loss of animals but increases cost

Pathogenesis:

inflammatory reaction to the cellular destruction that is occurring in the gut epithelium as merozoites are released

gut becomes flat = villous atrophy

clinically - birds in poor condition, depressed, soft faeces containing mucous and sometimes blood

gut won't work properly as epithelium will be destroyed

housing created perfect environment for parasite

good hygiene is a proven method against infection

Toxoplasma Gondii:

indirect life cycle

final host - any member of the cat family (domestic most important)

IMH = all mammals (including humans) + birds

*Cause abortion and perinatal mortality in sheep

Very rarely see overt clinical signs in an immunocompetent host

Pregnant ewe who has never seen parasite before = immunologically naive - cannot control infection and crossed into placenta and infects foetus

Infection late in pregnancy tends to produce infected, but normal lambs

Chocolate brown mummified foetus together with its own grey brown placenta

*oocysts are only shed for 1-2 weeks (young cats)

Tick-borne disease:

Major pathogens of ruminants (cattle) in tropical and sub-tropical regions of the world - associated with anaemia

*2 major species - spread over much of the world

T. Annulata = Europe, North Africa, East Asia

T. Parva = East/Central Africa

Death usually due to pulmonary oedema - die within 2-3 weeks of tick attachment due to drowning in own fluid

Control:

Acaracide dipping

Drugs

Vaccination

High frequency treatment needed

Expensive

Summary:

Protozoan parasites are major causes of animal disease

in UK and globally

Important genera include Eimeria, Toxoplasma

and Theileria

The relevance of protozoan parasites to zoonotic infection/public health and manipulation of the host cell will be covered during the course