NEW ORLEANS — Agriculture officials in Arkansas and Louisiana have warned veterinarians to watch for signs of a potentially fatal horse disease if there’s another drought this year.
The disease is often called pigeon fever because basketball-size abscesses in the chest and abdomen can give horses a pigeon-breasted look. It’s also referred to as dry-land strangles, as cases seem to spike in dry weather.
The disease has been reported in at least a dozen states in the past decade. Louisiana usually has fewer than three cases per year, but the state veterinary lab confirmed 33 during last year’s drought, said Sam Irwin, spokesman for the Department of Agriculture and Forestry. And, from what veterinarians have told her, the number may be far greater — perhaps as many as 300, Louisiana State University veterinarian Rebecca S. McConnico said.
Horse owners such as Kathryn Loewer, who gives riding lessons, runs horsemanship camps, sponsors a youth drill team and boards horses at Soaring Spirit Ranch near Crowley, don’t always spend the money to have the state lab confirm their animals’ diagnoses.
Mark Russell, an equine specialist at the University of Arkansas Cooperative Extension Service, said he’d heard of about a dozen cases in Arkansas, and there could have been more. “No one, that I could tell, had a lot of experience with treating it,” he said.
Experts say about 3 percent of infected horses develop internal abscesses, which are fatal if left untreated and often fatal even with treatment. External abscesses are more common but almost never lethal, although treatment can be messy.
The abscesses’ thick walls defy antibiotics, so the best treatment is having them lanced and drained by a veterinarian and then washing them out regularly with an antiseptic, McConnico said. The disease also can show up as inflammation and a line of sores and bumps in a horse’s leg and a series of small, painful pimples spread by contaminated blankets, grooming equipment, saddles and harnesses.
It’s not clear whether the bacteria that causes the disease is spreading or whether it’s in dirt all over and hot, dry weather just increases the opportunity for infection.
Brian Miller, a veterinarian who teaches at Colorado State University and runs its Equine Field Service, thinks it’s probably everywhere and outbreaks increase when dry weather turns the ground to dust that carries the bacteria into scratches and other small wounds. Once a horse develops abscesses, the disease can be spread by flies landing on the infected areas and then carrying the bacteria to other animals, he and others said.
Loewer quarantined her horses after two developed symptoms around the first of the year. That meant turning down an invitation for her drill team to perform. Both sick horses recovered, and none of the others was infected, she said.
“I wash my buckets. I bleach my buckets. I bleach my ground,” she said, while her horses were still in quarantine.
Bleaching the ground is probably not effective, but scrupulous cleanliness — including bleaching any hard surface the horse may touch — is a good idea, McConnico said. Other guidelines include wearing gloves when treating infected horses and changing clothes and shoes, as well as washing hands, before going from sick to healthy animals.
Spraying horses with fly repellant also can help since flies can carry the bacteria from an open sore to a small cut on a healthy animal, McConnico said.
Loewer said she thinks it’s significant that the horses that got sick had weaker immune systems. One is old, having turned 25 in February, and the other was “starved twice — I rescued her from the rescuers,” she said.
Michael Paton, a veterinarian with the Western Australia Department of Agriculture and Food, has studied the disease for 20 years and said it has two forms. One infects sheep and goats but not horses; the other infects horses but not sheep and goats. Both types can infect cattle and people, though human infections are rare. Vaccines exist for sheep but not horses.
Sheila McDonald, a veterinarian in Kelowna, British Columbia, estimated 400 to 500 horses in that area had pigeon fever in 2010 but said she didn’t hear of any cases last year. An outbreak in 1990 was followed by 20 years free of pigeon fever, she said.
McDonald said the outbreaks tend to be limited, and if flies carry the disease, they don’t take it far.
“It seems to get on a farm and spread horse to horse, but not too far in the neighborhood,” she said. “You may see it next door but not two blocks away.”