The Horse magazine recently published an article about T. gondii infection in humans as a result of consuming horsemeat. Two studies quoted in the article found that up to 30% of slaughtered horses and donkeys were infected with T. gondii or possessed T. gondii antibodies.
T. gondii is a parasite of warm-blooded animals, including humans. It has a worldwide distribution, causing the disease toxoplasmosis.
Toxoplasmosis in adult humans—especially the elderly and immune-deficient—can cause fever, pneumonia, heart disorders, muscular difficulties, lymphadenopathy, and death. Frequently, infection goes unnoticed in healthy adults. But the disease is of particular concern in pregnant women, as infected fetuses can develop eye, ear, skin, and nervous system disorders. It can also cause mental retardation and loss of vision in congenitally-infected children. It is also found in pork, lamb, and chicken.
Toxoplasmosis rarely causes clinical signs in horses, but can cause neurological problems such as ataxia and blindness in young or immune-deficient horses.
Additional references and sources of information:
This study follows 3 cases of toxoplasmosis caused by atypical strains probably acquired by from ingestion of raw horse meat imported from Canada and Brazil.
Patient 1 – 74 year-old male – passed away due to respiratory failure
Patient 2 – 23 year-old pregnant woman – delivered child with congenital toxoplasmosis
Patient 3 – 21 year-old pregnant woman – pregnancy terminated after ultrasonography-detected fetal severe abnormalities. Fetal necropsy showed numerous cerebral, cardiac, and hepatic abscesses with T. gondii
Other studies on T. gondii – http://www.ncbi.nlm.nih.gov/pubmed/?term=toxoplasmosis+horses
Consumption of raw or undercooked horsemeat can cause other parasitic infections as well – please also read these other studies on Trichinella in humans as a result of eating horsmeat:
High risk human infection via Trichinella in horsemeat – http://www.ncbi.nlm.nih.gov/pubmed/11099844
Trichinella outbreak affecting 550 consumers of horsemeat in France – http://www.ncbi.nlm.nih.gov/pubmed/9140477