Toxoplasmosis in adult humans—especially the elderly and immune-deficient—can cause fever, pneumonia, heart disorders, muscular difficulties, lymphadenopathy, and death.
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.
Equine infection occurs through ingestion of oocyst-contaminated pasture; complicating matters is the fact that oocysts are shed in great quantities and are particularly hardy, remaining viable for months in the open environment.
In a recent study, Fernanda Evers, DMVP, PhD candidate in the Zoonosis and Public Health department at the Universidade Estadual de Londrina, in Parana State, Brazil, and colleagues collected samples from 398 randomly chosen slaughter horses in six Brazilian states, which they tested using two different techniques. Combined, the techniques confirmed that 60 (15%) of the samples were positive.
Meanwhile, Chinese scientists were independently discovered a similar phenomenon in their country. Researcher Qiang Miao, PhD, of the College of Animal Science and Technology at the Yunnan Agricultural University in Kunming and colleagues tested 266 horses and 133 donkeys in slaughterhouses for T. gondii infection. They found that 81 (30.5%) of the horses and 27 (20.3%) of the donkeys were positive for T. gondii antibodies, according to their published report.
Although the disease can be dangerous in humans, few horses are affected. Toxoplasmosis rarely causes clinical signs in horses, but can cause neurologic problems such as ataxia and blindness in young or immune-deficient horses.
The study, “Diagnosis and isolation of Toxoplasma gondii in horses from Brazilian slaughterhouses,” was published in Revista Brasileira de Parasitologia Veterinária.