Sheep Displayed No Clinical and Parasitological Signs upon Experimental Infection with Babesia aktasi

Our survey in the Mediterranean region of Türkiye revealed high prevalence of Babesia aktasi in goats, while no molecular evidence of the parasite was found in sheep grazing in the same pasture. We hypothesized that the parasite may not be infectious to sheep. To test this hypothesis, the present study was designed to evaluate the susceptibility of Akkaraman sheep breed to B. aktasi infection. Fifteen mL of fresh blood infected with B. aktasi was injected into immune-suppressed lambs (n = 5). The recipient lambs were monitored daily for clinical signs of babesiosis over 30 days, and blood was collected for microscopic and molecular diagnostic evaluation. The lambs did not display clinical and parasitological signs of babesiosis. Two out of five recipient lambs were nested PCR-negative for B. aktasi over 30 days post infection. Out of the remaining three lambs, two were PCR positive on the first day, and one recipient was positive until the fourth day post infection. DNA sequencing confirmed that the PCR positivity in the recipient lambs originated from the inoculum. These findings revealed that immune-suppressed sheep do not appear to be susceptible to infection with B. aktasi that is lethal to immune-suppressed indigenous goats.