A survey on Apicomplexa protozoa in sheep slaughtered for human consumption

Infections with the Apicomplexa Toxoplasma gondii, Neospora caninum, and Sarcocystis spp. are common causes of reproductive disorders in sheep. However, few epidemiological studies regarding co-infections with these three protozoa are reported in sheep in Italy. For this reason, this study aims to evaluate possible co-infections with T. gondii, N. caninum, and Sarcocystis spp. in sheep slaughtered for human consumption. From April to July 2019, individual blood, brain, heart, and diaphragm samples were collected from 138 sheep after slaughtering. The presence of IgG anti-Toxoplasma in serum samples was evaluated through ELISA. DNA of the three protozoa was investigated using specific PCRs. Co-infection with T. gondii, N. caninum and Sarcocystis spp. was found in 66.7% of the examined sheep. Antibodies against T. gondii were found in the 36.2% of serum samples. The presence of T. gondii DNA was detected in the 67.4%, 77.5%, and 21.7% of the brain, heart, and diaphragm samples, respectively. Neospora caninum DNA was found in 72.5% of the examined brain samples. Sarcocystis spp. DNA was detected in 92% and 52.2% of the heart and diaphragm samples, respectively. Sequence analysis of the Sarcocystis spp. revealed the sole presence of Sarcocystis tenella. The present study demonstrates that sheep have a high risk of infection with the three Apicomplexa investigated, suggesting the need to adopt adequate measures to prevent the spread of these parasitic infections considering their clinical and economic impact on ovine production. Furthermore, the possible role sheep play in the zoonotic transmission of toxoplasmosis to humans was highlighted.