http://www.pork.org/filelibrary/Factsheets/PorkSafety/toxoplasma04494.pdf
Toxoplasma and pork
Most species of livestock, including
sheep, goats, and pigs, are susceptible to
infection with Toxoplasma gondii; however,
animals exposed to T. gondii rarely
show signs of infection. Animals are
infected in a similar manner to humans:
ingestion of oocysts from the environment;
consumption of infected animals
such as mice, birds, and other wildlife;
consumption of undercooked meat
scraps; and in some species, through in
utero transmission.
Prevalence of Toxoplasma gondii in
pigs varies, but generally exceeds 10-20%
in most countries. Infection rates are
higher in breeding populations than in
market pigs, reflecting that length of
exposure is a factor in acquiring T. gondii
infection. A number of serologic surveys
for T. gondii have been conducted in the
U.S. (Table 1). Infection was estimated at
23.9% of pigs in 1983-1984 with higher
rates in breeders (42%) than in market
pigs (23%). When pigs from these same
areas were tested in 1992, the percentage
had dropped to 20.8% of breeders and