After all the publicized concern about the presence of phenylbutazone (Bute) in horsemeat, researchers now fear the meat could also carry the organism that causes toxoplasmosis—a potentially deadly human disease. Recent study results suggest that up to 15% of horses in Brazilian slaughterhouses and 30.5% of those in southwest China could be infected with Toxoplasma gondii.

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.

In 2011, French researcher Christelle Pomares of the Université de Nice–Sophia Antipolis–Inserm, in Nice, reported three cases of toxoplasmosis infection in humans in France, most likely from consuming horsemeat. The cases included the death of a 74-year-old man and abortion in a 21-year-old woman due to severe fetal abnormalities. The horsemeat probably came from Brazil or Canada, according to the strain analysis, Pomares reported.

Toxoplasmosis has long been associated with cats as “carriers” of the disease caused by T. gondii oocysts—an egglike parasite structure, researchers say. Cats don’t necessarily “carry” the disease itself, but unlike other warm-blooded animals, they shed the oocysts in their feces