Protozoa: Toxoplasma gondii Flashcards
1
Q
What type of life cycle does T. gondii have?
A
Indirect
2
Q
What are the hosts involved in T. gondii life cycle?
A
IMH - all mammals/birds
FH - felids
3
Q
Describe the life cycle of T. gondii
A
- Cat ingests prey infected with cysts e.g. bird, rodent
- Cysts rupture in the stomach, invade gut epithelial cells and undergo asexual reproduction to produce micro and macrogametes
- Gametes fuse to form a zygote which develops into an oocyst which is released into the gut
- Shed in faeces. After 24 hrs oocyst becomes sporulated under warm, moist conditions
- Sporulated oocysts ingested by IMH e.g. sheep, bird, rodent
- Oocysts rupture in IMH host stomach releasing sporozoites
- Sporozoites form tachyzoites which spread via lymphatics and blood vessels and can infect any cell in the body
- Acquired immune response attempts to control infection
- Tachyzoites form bradyzoites that generate cysts which locate in muscle, neural tissue and organs to evade immune response
- Bradyzoites become activated once ingested by FH
4
Q
State the effects infection can have in the pregnant ewe.
A
- Infection within 50/55 days gestation - death of foetus, expulsion/resorption. Rate of barren ewes higher than expected.
- Infection within 50/120 days gestation - Premature still born/weak lambs. May get rotten lambs.
5
Q
How is T. gondii diagnosed in sheep?
A
- Clinical history
- Placental lesions
- Diagnostic tests - antibody, immunohistochemical detection of parasite, PCT of placental sample
6
Q
What appearance do the placental cotelydons of infected ewes have?
A
- Bright to dark red
- Covered in small white foci (2mm)
7
Q
Describe the measures put in place to control ovine toxoplasmosis
A
- Covering feed and preventing cats from accessing feed stores
- Not feeding farm cats raw meat
- Disposing of carcasses properly
- Retain ewes that are immune
8
Q
What vaccine can be given to sheep?
A
Toxovax
