With water pooling in places that it normally doesn't and sharp debris all around, horse owners can't help but wonder if conditions left by Hurricanes Katrina and Rita will cause an increase in the reports of illnesses such as tetanus, encephalitis, botulism, and Potomac horse fever. Area veterinarians say they haven’t seen an increase of horses exhibiting these diseases, but they're remaining on guard should any hurricane-related cases flare.

Shannon Gonsoulin, DVM, owner of All Creatures Animal Hospital in New Iberia, La., helped rescue and treat horses after both hurricanes. "The biggest threats are, in the immediate term, tetanus, and in the long-term, mosquito-borne viruses," he says.

Tetanus--By far the most equine cases Gonsoulin has seen directly related to the hurricane have been lacerations from debris. "Fortunately, we recommend the tetanus vaccine quite frequently down here," he said. "We haven't had any tetanus cases at this point that have developed in association with either hurricane. I'm sure there's one or two that we might not have noticed, but tetanus seems to be under control."

Becky McConnico, DVM, PhD, Dipl. ACVIM, associate professor of Veterinary Medicine in Louisiana State University's Equine Health Studies Program, has seen one case of tetanus that she believes is attributable to a Katrina-related injury. The horse was not vaccinated against tetanus.

Encephalitis--There are differing opinions on the exponential growth of mosquito populations and their likelihood to cause outbreaks of encephalitis such as Eastern equine encephalitis (EEE) and West Nile virus (WNV). Katrina and Rita left standing water all over the Gulf Coast regions, creating ideal mosquito-breeding conditions.

"The encephalitis issues are going to be something that we're going to be really cautious of," said Gonsoulin. "Most of the horses down here are vaccinated against encephalitis because we have a mosquito-infested area. If we don't have a very cold winter, it's going to make the mosquito season an even longer timeframe."

But even though there could be a bumper crop of mosquitoes, McConnico says mosquitoes and birds that were carrying encephalitides "got 'blown away,' literally! We have less cases of WNV than in years past. The huge 'swamp' mosquitoes blowing in from Rita's wrath do not carry WNV or EEE, as I'm told by the local veterinarians in that area."

Entomologists and veterinarians had earlier told The Horse that while they expected an increase in mosquitoes, they did not expect increases in WNV. They were concerned about EEE, however, which has a higher mortality rate than WNV. (For more information, click here.)

Botulism--Still another post-hurricane concern could be botulism, which sometimes appears in areas where soil has become warm and moist for an extended period of time or where there are decaying or decayed bits of forage and/or dead animals. Horses get botulism when toxins from the bacterium Clostridium botulinum are introduced into their body by either ingestion or contamination of wounds. C. botulinum can also grow in young horses' gastrointestinal tracts (toxicoinfection botulism) after the animals ingest spores in their environment. The toxins produced by C. botulinum can cause weakness since they block the connection between nerves and muscles and eventually paralyze the horse.

So far, there doesn't appear to be any influx of horses with botulism as a result of the hurricanes. Part of the reason could be horses aren't grazing in areas where carcasses remain from the storm, because in those areas the grass has been killed by the salt water.

"Right now they're trying to pick up all the dead carcasses they can and burn them to decrease the chance of a botulism exposure," Gonsoulin said. "Unfortunately, a lot of these carcasses have washed out to some of the marshes that are pretty remote, but by the time the horses get back on those pastures where the salt waters have caused issues, the carcasses will probably have been gone long enough to the extent that botulism wouldn't be an issue."

Other Nasties--McConnico says other types of hurricane-related disease that could appear in the coming months are pythiosis (disease caused by a water-borne agent and characterized by large, roughly circular, granulomatous or chronically inflamed, ulcerated, fistulated nodules or subcutaneous swellings with yellow-gray necrotic masses or cores) and other fungal skin diseases. Additionally, she anticipates there could be an increase in corneal disease secondary to ocular trauma from debris.

Other veterinarians have suggested that ingestion or exposure to another agent, Leptospira spp could be on the rise. Leptopsirosis can cause abortion, infertility, lowered milk production, and equine recurrent uveitis (moon blindness), and it is thought to be contracted through ingestion of contaminated soil or feedstuffs, or through cuts. At least one veterinarian has suggested there might be more uveitis cases on the horizon because of conditions left by the hurricanes.

Potomac horse fever (another disease that tends to show up in some areas of the country as a result of wet weather) isn't found in Gulf Coast areas, but veterinarians say to stay tuned, because one never knows if it will begin to appear.

Gonsoulin concluded, "We're still in the infant phase, and we're not sure what we might see. We're hoping for the best and expecting the worst for any kind of disease outbreaks."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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