PA9: Coccidian protozoa Flashcards
(12 cards)
Characteristics of coccidian protozoa
Indirect lifecycles (heteroxenous protozoa) with definitive & intermediate hosts
Intracellular with parasitophorous vacuole
Form tissue cysts
Sexual & asexual reproduction
Give examples of coccidian protozoa
Toxoplasma gondii
Neospora caninum
Sarcoystis spp.
What are natural hosts for T. gondii?
Intermediate: mice
Definitive: cat
How is transmission of T. gondii increased?
A bradyzoite cyst in the mouse brain can alter the natural cat avoidance behaviour.
Where do the bradyzoite cysts of T. gondii form in sheep?
In muscle
How does T. gondii affect sheep?
In pregnant sheep, the trachyzoite migrates to the uterus/placenta which results in foetal death/abortion.
If infected during early pregnancy, it is unnoticed as it is just the embryo’s resorption.
If infected during middle of pregnancy, it leads to foetal death & mumification/foetal developmental retardation due to inadequate nutrition + foetal infection.
If infected in late pregnancy, freshly-dead lambs are aborted/weak lambs are born.
Control of T. gondii
Good hygiene
Good cooking of meat
Washing vegetables & fruits & ustensils
Piglets can be vaccinated with S48 tachyzoites
What are the hosts for Neospora caninum?
Definitive host: dogs
Intermediate host: cattle
How is Neospora caninum usually transmitted to cattle?
Via the trans-placental route
What is the effect of Neospora caninum on cattle?
Abortion
What are the clinical signs associated with Sarcocystis spp.?
In carnivores clinical signs are rare. Occasional mild diarrhoea.
Oocysts shed by dogs usually don’t cause clinical signs in ruminants but occasionally result in organ dysfunction, death, neurological disease.
Oocysts shed by cats cause large thick cysts in tongue, oesophageal or abdominal muscles.
How is Sarcocystis spp. controlled?
Not giving dogs & cats raw meat/carcasses.
Preventing dog/cat faecal contamination of pastures, feed & bedding.
