An investigation into bovine besnoitiosis (Besnoitia besnoiti) in an Irish pedigree Aberdeen Angus herd

This case report describes the investigation of the first outbreak of bovine besnoitiosis in a beef/suckler herd in Ireland. Infection with Besnoitia besnoiti was suspected by the attending veterinarian following clinical examination of a chronically affected cow with areas of alopecia and marked skin thickening. Diagnosis of besnoitiosis was confirmed by Cork Regional Veterinary Laboratory based on histopathology of skin biopsies. Subsequent serological investigation using enzyme-linked immunosorbent assay testing revealed a 17.8% seroprevalence within the herd, with 33% of adult cows seropositive. A clinical whole-herd investigation found an overall clinical prevalence of besnoitiosis of 38.8%, based on the presence of sclerocysts and/or vulval cysts. There was poor agreement between serological and clinical findings. In contrast to serological findings, 83.8% of 18-month-old heifers and bulls had sclerocysts. Due to the high prevalence of besnoitiosis and the challenges of controlling spread, this pedigree herd was discontinued by the farmer.