Black Disease in Merino sheep infected with Thysanosoma actinioides in Patagonia Region, Argentina

An outbreak of Black disease in Argentinean Patagonia where 80 sheep out of 1200 Merino ewes suddenly died, is reported. Big amounts of fluid in the t horacic and abdominal cavities, the presence of focal coagulative necrosis in the liver parenchyma and plenty Thysanosoma actinioides specimens in bil e ducts were the most important findings observed at necropsy. Clostridium novyi was early detected in liver smears through immunofluorescence. Later, Clostridium novyi type B was isolated from liver cultures. Due to the abse nce of the commonest predisposing agent, i.e. Fasciola hepatica, the severe parasitism by Thysanosoma actinioides is proposed as the predisposing fact or of the present outbreak of Black disease.