Epidemiological survey on the occurrence of Anaplasma phagocytophilum infection in sheep reared in central Italy

Anaplasma phagocytophilum is a tick-borne pathogen of sheep and other ruminants, humans, horses and dogs. Current data on the prevalence and diffusion of A. phagocytophilum among domestic animals in Italy are fragmentary, especially those related to sheep, considered a natural domestic reservoir. We investigated the prevalence of A. phagocytophilum infection in dairy sheep from Tuscany (Italy), by testing 624 sera with the immunofluorescent antibody (IFA) test. The sera belonged to 33 different flocks distributed throughout the province of Grosseto (Tuscany). Positive results were found in 21 out of the 33 flocks tested (63.63%, 95% IC 47.22–80.05%) with a prevalence rate within flocks ranging from 3.33% to 59.26%. The seroprevalence against A. phagocytophilum within the sheep population was 8.01% (95% IC 6.13–10.41%), and most of the positive cases showed low antibody titres (1/40-1/80). The multivariate analysis identified “small flock” (<300 animals) as the factor most closely related to serological positivity. Our results reveal a moderate circulation of A. phagocytophilum among sheep flocks in central Italy