Investigation of an Autochthonous Outbreak of Bovine Besnoitiosis in Northwestern Sicily

Bovine besnoitiosis is a parasitic disease caused by the protozoan Besnoitia besnoiti, leading to infertility in bulls and abortions in cows. In Italy, it is considered an emerging disease, recently introduced by the importation of animals from Spain and France. In the last decade, many outbreaks have been reported and confirmed in native cattle, mostly in northern and central Italy. This study reports on an autochthonous outbreak of bovine besnoitiosis in two nearby farms located in northwestern Sicily. A 15-month-old Limousine bull born on the farm showed typical clinical signs of the chronic disease phase, such as edema of the scrotum with subsequent hyperkeratosis associated with eschars and thickening of the skin. A histopathological examination revealed the presence of Besnoitia tissue cysts containing bradyzoites in the eyes, tendons, testicles, dermis, and nictitating membrane. A serological investigation using a commercial ELISA kit revealed a high seroprevalence of the antibody anti-B. besnoiti (79.2% for the farms in this study). Clinical disease showed low prevalence (1.5%) despite the high seroprevalence of specific antibodies in the herd, confirming that bovine besnoitiosis is an emergent endemic pathogen in Sicily, but its clinical behavior still remains sporadic.