This month’s article is about a disease called “Pigeon Fever”. This disease is also known as pidgeon breas, dryland distemper and dryland strangles. The disease is caused by a bacterium called Corynebacterium pseudotuberculosis. Most cases occur in the fall, but it can occur anytime.
The most obvious signs of the disease are external abscesses that are commonly seen around the pectoral muscles of the horse’s chest. These abscesses can cause the chest to protrude much like a pigeon’s breast and hence the name. The abscesses can also be found on the abdomen and groin area. In rare cases, abscesses can also form internally. Other symptoms can include lameness and reluctance to move.
The bacteria can live in the soil and then infect the animal by gaining access through sores and abrasions in the skin. It is also commonly believed that biting flies can also spread the disease. Once infection occurs, the disease goes through an incubation period and it may take weeks for abscesses to develop.
A diagnosis of this disease is often presumptive based on the clinical signs. If other abscess forming diseases such as true strangles is suspected, a culture should be taken.
Treatment includes lancing and draining of abscesses. It is sometimes difficult to locate the abscess due to the surrounding swelling and the fact that the abscesses are often very deep. Occasionally an ultrasound exam of the area is done to locate the fluid filled abscess. The material that drains from the abscess should be collected and disposed of to minimize spreading to other horses. The wounds are typically flushed daily with a dilute betadine solution until the wound heals. Non-steroidal anti-inflammatories are also used to help with pain and swelling. The use of antibiotics is controversial. It is believed that antibiotics may prolong the course of the disease. Typically procaine penicillin G and trimethoprim sulfa antibiotics are used. As always, it is imperative that antibiotics be used at the proper dosage and for the proper duration. Long term antibiotic therapy is indicated in cases of internal abscesses because they cannot be drained and the fatality rate for untreated internal abscesses can approach 100 percent.
Prevention is difficult since the disease can become endemic in certain areas. Generally, good hygiene practices including fly control will minimize the spread of the disease. Quarantining infected horses and thoroughly disinfecting contaminated items is critical.