Brucellosis is a highly contagious zoonotic disease that occasionally affects horses and donkeys however predominately affects cattle, sheep, goats, bison, deer, buffalos, elks, pigs, and dogs. Humans are also at risk of brucellosis. Brucellosis is caused by the bacterium Brucella
, primarily B. abortus
and B. suis
. The disease is characterized by recurrent abortion and infertility. However, in horses it frequently manifests as Fistulous withers
and Poll evil. A survey conducted on 85 horses with fistulous withers revealed that B. abortus
was isolated from 80% of the affected horses. Of those horses with B. abortus
infection, 92% had reported contact with cattle.
species are transmitted by ingestion, inhalation, or direct contact through skin abrasions or mucous membranes. Most horses acquire the infection from contact with cattle.