February 2015

​Necropsy of a black Angus calf

An owner in Alva, Oklahoma lost 5 to 6 calves that were 4-6 weeks of age to an unknown illness. The calves were treated with several different antibiotics prior to death. Necropsy revealed mild inflammation of the small intestine, small 1/2 cm diameter hemorrhages in the cecum, and loose green stool throughout the intestinal tract. A fecal flotation was performed on a cecal wall scraping and the following organism was observed.

100X total magnification

400X total magnification:

What is your diagnosis?

Case kindly provided by Dr. Jerry Ritchey, anatomic pathologist and professor at Oklahoma state University Center for Veterinary Health Sciences. Photos provided by Becky Duncan-Decoq, research technician at the Oklahoma Diagnostic Laboratory at Oklahoma State University.

Answer

These are oocysts of Eimeria zuernii, a causative parasite of winter coccidiosis. The onset of clinical signs corresponds with parasite gametogony within the intestinal tract and the associated destruction of mucosal cells. Tenesmus and bloody diarrhea are typical clinical findings. The pathologist remarked that the level of infection and tissue destruction was the worst that he had seen in a coccidiosis case