Page 58 - July 2017

Since the incubation period is variable and can be 3 to 4 weeks or longer, there may no longer be a break in the skin . . . by the time the abscesses mature enough to be noticed.
After the bacteria get through the skin, they travel inside white blood cells and the infection can course through the lymphatic system until an immune response is developed.
mineral supplement blocks for cattle that con- tain insect growth regulators.
“Unfortunately, there’s no real proactive way to prevent pigeon fever,” says Slovis. “There was
a vaccine available for a time, but it has been removed from the market. Hopefully in the future, there will be a vaccine we can use. The best thing we can do for prevention is fly control,” he says.
Boehringer Ingelheim was granted a condi- tional license for their pigeon fever vaccine in early March 2015, but halted sale of that vaccine later that year. The company voluntarily withdrew it after several adverse reactions (GI tract problems) were reported in some of the vaccinated horses. The vaccine presented more risk than expected.
Even though there is no vaccine currently available, there are things horse owners can do in terms of prevention such as practice good bios- ecurity and general disease prevention: washing hands, not sharing water buckets, not dunking the hose in the water bucket and not letting the hose be in multiple buckets, keeping stalls clean, and keeping flies down.
Slovis points out that pigeon fever can affect any horse, anywhere, any time, so horse own-
ers need to keep it on their radar. It’s not like strangles; it’s not a contagious disease that will sweep through your herd, but it can affect multiple horses in a herd. Some horses seem more prone to it than others, but we don’t know why,” Slovis says.
TreaTmenT
When a horse comes in for diagnosis with possible pigeon fever, ultrasound is often used to evaluate the abscess. “If it’s a superficial abscess, we drain it,” says Slovis. “If it’s deep, we put the horse on systemic antibiotics if there are clinical signs like fever or lameness. But if the horse is not showing clinical signs, we’ll just drain and flush the abscesses and not use antibiotics,” he says.
If a horse develops pigeon fever, work with your veterinarian for treatment. “Internal infections and ulcerative lymphangitis require antibiotics, while the uncomplicated external abscesses usually do not,” says Spier. “Every case is different, so you should have the horse looked at by a veterinarian and monitored for signs of internal infection. The infection can hopefully be resolved faster by opening and draining/flushing external abscesses, which often requires sedation and minor surgery,” she says. Draining, flushing, and getting rid of the pus can prevent further contamination of the pasture.
“You can’t rush it, however. The horse is developing an immune response at the same time the abscesses are forming,” says Spier. Pectoral abscesses must also come to a head before they can be successfully lanced and drained. Some abscesses are just under the skin, while others are deep and under the muscles. Ultrasound can be useful for finding the
deeper abscesses and judging their maturity and readiness for drainage. Contents of the abscess and the flushing material, such as saline with antiseptic solution added, should be col- lected and disposed of.
“We don’t treat it as a contagious disease at our hospital,” says Slovis. “We don’t quarantine the animal. We just use proper hygiene when handling the horse, and wash our hands, wear gloves, just common sense things.” Care is taken to make sure none of the infective mate- rial is spread to other patients.
“When you lance and open the abscesses, you don’t leave the pus all over the floor because flies will feed on it and potentially infect other horses. A person has to be careful with it and try to collect the pus in a trash bag when the abscess is lanced. It comes down to basic hygiene,” Slovis explains.
This bacterium is susceptible to many com- monly used antibiotics, but the intracellular loca- tion inside the macrophages and the presence of large amounts of pus within a thick abscess cap- sule make it difficult for some antibiotics to have much affect. Your veterinarian can help decide whether antibiotics should be used and what types might be most effective in each individual situation. This disease should not be indiscrimi- nately treated with antibiotics, and horse owners should not attempt to lance and drain external abscesses on their own. “The horse might have an internal abscess that they’ll miss,” Spier says.
56 SPEEDHORSE, July 2017
equine health