As fall approaches, veterinarians are urging horse owners to be on the look out for cases of pigeon fever, also known as dryland strangles and dryland distemper. The disease is caused by Corynebacterium pseudotuberculosis, a bacterium that causes abscesses in affected horses.
Warm fall weather bringing more chances of pigeon fever in horses
The bacteria that causes pigeon fever survives in the soil and is spread to horses primarily by flies or through open wounds, occurring most commonly in the fall during periods of dry weather.
The disease is called pigeon fever not because it’s spread by pigeons, but because the abscesses caused by the bacteria frequently localize in the chest muscles and ventral abdomen of the horse giving the horse’s chest a pigeon-breasted appearance. Pigeon fever was first diagnosed in 1915 in San Mateo, California, but is now routinely found throughout the arid regions of the West and Midwest.
Most outbreaks occur during periods of high climatic temperatures and dry conditions, and it appears the recent drought conditions across the United States have aided the disease in moving as far east as Kentucky and Florida, although no statistics have been compiled that horse owners and veterinarians can rely on for future predictions.
The disease generally subsides during winter after fly season is past, but in southern parts of the country fly season is long and a good freeze is needed to reduce the incidence of cases. In some years that until late November, even up in the mountains.
The bacteria that causes pigeon fever survives in the soil and is spread to horses primarily by flies or through open wounds. It occurs most commonly in the fall during periods of dry weather when the population of insects around horses increases.
Initially horses may appear lethargic, reluctant to move and have a fever. But these signs are typically accompanied by deep external abscesses that appear in the muscles of the breast, underside of the abdomen and groin area, the udder or sheath.
Pigeon fever can also manifest as internal abscesses which are very difficult to treat, or as ulcerative lymphangitis, a limb infection. The external abscess form is the most common and the prognosis is generally good. The external abscesses can range from small contained areas of infection to severe massive deep abscesses containing large volumes of tan pus.
Because the bacteria is contagious and can easily be transmitted to other horses on the farm timely veterinary care is important.
The infections need to be accurately diagnosed and appropriately treated. Infected horses should be isolated, with proper disposition of any infectious material, followed by complete cleaning/ disinfection of contaminated areas.