Primarily a disease of horses, mules, and donkeys. Incidence Seldom occurs in humans. No naturally acquired cases have occurred in the United States in almost 60 years.
Cases continue to occur in Asia, Africa, the Middle East, and South America.
Sequelae Systemic invasion can occur with resulting chronic abscessation. Transmission Generally transmitted from animals to humans. Has been considered a possible agent of bioterroristic attacks. Risk Groups Veterinarians, horse and donkey caretakers, abattoir workers, workers in laboratories where the organism is being handled or in areas where equines may be infected. No national or state surveillance exists.