A long-term serological survey of Toxoplasma gondii in European bison (Bison bonasus) – the largest european herbivore

Zoonotic parasites are among the most prevalent agents that impair health and form networks of interdependencies between wildlife, domestic animals, and human populations. Toxoplasma gondii is a protozoan parasite that causes one of the most common zoonotic diseases worldwide - toxoplasmosis. It can be transmitted horizontally through contaminated food or water, or vertically through the placenta. The study aimed to estimate the prevalence and distribution of T. gondii seropositivity using an in-house ELISA in free-living and captive European bison from two populations in north-eastern Poland. A long-term survey spanning more than 20 years revealed that IgG antibodies to T. gondii were present in 4.1% (15 of 367 tested European bison). All individuals seropositive for T. gondii originated from the Białowieża Forest. They were found in supplementary-fed herds on the forest's edge, near human settlements, and in captivity. No European bison seropositive for T. gondii were found in the Knyszyn Forest. Our study revealed that European bison, the largest European herbivore, have been exposed to T. gondii for a long time, since 1996. It also showed that management practices, including supplementary feeding, can increase the risk of T. gondii transmission both in free-ranging and captive European bison. Therefore, feeding sites with stored hay, used by both European bison and cats, may serve as a source of toxoplasmosis. Epidemiological studies of toxoplasmosis in European bison are important, as this parasite poses a potential health risk to this rare species and may impact its conservation and management.