Mosquito-Borne Disease

"We don't yet have information to suggest that horses become infected with Zika or develop disease, and there are certainly horses present in many parts of the world where Zika Virus is present," observes Martha Mallicote, DVM, a veterinarian in Large Animal Medicine at the University of Florida in Gainesville.

"Most of the human cases that have occurred in the U.S. have been related to travel or intimate contact with someone infected," she explains. "Theoretically, the conditions are not right for Zika to be an endemic disease here in the U.S., but it would be dangerous to think that it could never happen. The risk for horses to become infected seems fairly minute at this point and the concern for human infections is much more important."

Even if Zika never becomes an issue in the equine population, there are already enough mosquito-borne diseases that do infect horses.

Horses owners shouldn't be worried about mosquito-borne diseases, but they should be concerned, aware and proactive.

While less likely to result in death to the horse than encephalitis, WNV can require extensive veterinary treatment and affected horses may suffer long-lasting neurologic deficits.

"Other than West Nile, which most horse owners are now aware of, we must also remain committed to continued vaccination against the 'older' mosquito-borne encephalitis viruses," cautions Mallicote.

Vaccination is Crucial

"The vaccines that are available are effective and inexpensive. The frequency that those vaccines should be used varies, depending upon region and mosquito presence throughout the year," says Mallicote.

"In Florida, for example, horses are vaccinated for these diseases two to three times annually. These vaccinations should not be skipped, particularly in areas like the Southeast, Gulf coast, and Southwest where mosquitoes are present much of the year."  

It's important to discuss vaccination with your veterinarian to come up with a vaccination schedule that fits your particular horse and where you live. Strategic vaccination is very effective when it comes to protecting horses and ensuring immunity to these diseases is at its best during mosquito season.

Fight Back Against Mosquitoes

The war against mosquitoes involves more than vaccination. Take a good look at your property and stable management practices to see how you can markedly reduce exposure to mosquitoes.
"Just as important as vaccination is the use of mosquito control. This will ultimately protect the horses, humans and any other at-risk species that may be present on the farm," says Mallicote.

Because female mosquitoes lay their eggs in or around water, any standing water is prime mosquito breeding ground, so take steps to eliminate it. Even a tin can or coffee cup that catches rain water can breed disease-vectoring mosquitoes.

Get rid of damp vegetation, brush, weeds and leaves around the barn where mosquitoes can hang out in the heat of the day. This includes cleaning out gutters regularly.

Make your horse less appealing to mosquitoes by taking practical steps:

• Use equine insect repellent products designed to repel and kill mosquitoes
• Reduce the amount of body exposure to mosquitoes by using fly sheets and fly masks
• Whenever possible, avoid turning horses out at dawn and dusk, as these are peak mosquito activity times (One study showed that mosquito activity increased by 500% during a full moon!)
• Use fans in stalls and throughout the barn to make it more difficult for mosquitoes to land and feed on horses 

"We have not yet identified equine cases of some of the more novel mosquito-vectored diseases that are being seen in humans in Florida and the Caribbean," notes Mallicote, "but that does not mean it won't occur in the future. Stay tuned on that front."