Changes

===Congenital Transmission===

===Congenital Transmission===

 

not carnivores, consumption of tissues infected with

Apart from ingestion of oocysts in the environment, the only other method of transmission of toxoplasmosis to sheep is vertical spread from mother to foetus during pregnancy. This is because sheep are herbivorous, and do not consume animal tissues containing cysts. The outcome of transplacental infection depends on the stage of pregnancy. Infection in early gestation usually causes foetal death, as the foetal immune system is immature at this stage. In mid-gestation, infection may cause the birth of weak or stillborn lambs, sometimes accompanied by a mummified sibling. Ewes infected in the third trimester normally give birth to infected but clinically normal lambs.

 

is not considered to be a route of transmission in

As well as in acute infection of the damn, transplacental transmission may occur as a result of recrudescence of an endogenous infection.

these animals. The only other route of transmission

is vertical from mother to foetus during pregnancy

(Buxton and Rodger, 2008). The stage of pregnancy

when transplacental transmission of T. gondii takes

place is important in determining the clinical outcome.

If infection occurs early in gestation, when the

foetal immune system is relatively immature, foetal

death is likely to occur. Infection at mid-gestation

may have an accompanying small mummified foetus,

whereas infection in later gestation may result in

birth of a live, clinically normal, but infected lamb

(Buxton, 1990). The birth of clinically normal but

infected lambs usually occurs as a result of a primary

infection in the third trimester of pregnancy,

although it is also possible that transplacental transmission

may occur as a result of recrudescence of an

endogenous infection (Trees and Williams, 2005).

===Recrudescence of Endogenous Infection===

===Recrudescence of Endogenous Infection===