Cases of a rare parasitic disease surfaced in U.S. donkeys in 2011, prompting a group of Cornell University researchers and colleagues to examine the condition—called besnoitiosis— more closely. One veterinarian described the disease, which is characterized by the development of cystic lesions both externally and in the throat and eyes, and weighed in on its detection and treatment at the 2011 American Association of Equine Practitioners convention.

"Besnoitiosis has recently been diagnosed in donkeys from several states on tissue and blood samples sent to Cornell University," explained Sally Ness, DVM, an internal medicine resident at the College of Veterinary Medicine’s Equine and Farm Animal Hospital. During her presentation at the convention, held Nov. 18-22 in San Antonio, Texas, Ness said the disease might be far more common in donkey populations than previously thought.

Besnoitiosis is caused by a protozoan parasite that is known to affect multiple host species worldwide.  Cases are found primarily in Africa and Asia; however, recent outbreaks in European cattle populations suggest the disease could be spreading globally. Besnoitiosis in donkeys and horses is caused by Besnoitia bennetti, a coccidial parasite (a single-celled obligate intracellular parasite) that infects the animal, growing within tiny cysts in the skin, organs, and even the eyes of affected animals. So far, the only known cases of besnoitiosis in North America are in donkeys.

Ness and her team have examined donkey herds in the Northeastern and Northwestern United States with the goal of learning more about the clinical