Haemoparasitic agents associated with ovine babesiosis: A possible negative interaction between Babesia ovis and Theileria ovis

Abstract

Babesiosis, theileriosis, and anaplasmosis are the most common tick-borne diseases in sheep. The majority of anaplasmosis and theileriosis are subclinical; however, babesiosis causes severe infections in small ruminants. Although there are many reports of co-infections with the agents of these diseases, their clinical severity compared with either of the infections alone is unknown. Within the host, interactions between co-infecting species may cause variations in clinical presentation and response to therapy. The aim of this study was to determine the tick-borne agents in sheep located at sites where fatal disease outbreaks caused by babesiosis have commonly been reported. Two hundred and nine sheep with clinical signs suggestive of ovine babesiosis were included in the study. The initial diagnosis of haemoparasites was based on clinical symptoms and microscopy and was confirmed using PCR assays. The blood samples were examined for the presence of Babesia ovis (B. ovis), Anaplasma ovis (A. ovis), A. phagocytophilum, and Theileria ovis (T. ovis). The results showed 86.12% of the animals were infected with one or more pathogens. B. ovis was the dominant pathogen. Overall, the infection rate of B. ovis, A. ovis, T. ovis, and A. phagocytophilum was 70.81%, 56.94%, 21.05%, and 2.39%, respectively. The infection rate of B. ovis alone (31.11%) was higher than A. ovis (9.44%) or T. ovis (1.67%) alone. Co-infections were found at a higher percentage (57.78%) than single infections (42.22%). A. ovis was detected in the blood of a high percentage (98.07%) of co-infected animals. Coexistence of B. ovis and A. ovis (34.45%) was more common than other combinations of species. There was a noticeably low level of co-occurrence between B. ovis and T. ovis (1.11%). During the study, 11 sick animals did not survive despite treatment. Seven were infected with B. ovis alone, three had a dual infection with B. ovis and A. ovis, and one had B. ovis, A. ovis, and T. ovis.