By TIM THORNBERRY
Kentucky Correspondent

FRANKFORT, Ky. — This year’s April showers brought more than May flowers; it brought the threat of a large mosquito infestation, something the Kentucky Department of Agriculture (KDA) is asking horse owners to consider when it comes to vaccinating for West Nile Virus (WNV).

The disease, which historically begins showing up in Kentucky horses in July, was first identified in Kentucky’s equine population in the fall of 2001 with a total of 683 horses being diagnosed within the past 10 years, according to information from the KDA. The agency notes the number of cases usually increases throughout the summer before peaking in mid-September.
But proper vaccinations can protect the equine population from getting the disease.

“Since 2003, no horses known to have been properly vaccinated have gotten West Nile in Kentucky,” Agriculture Commissioner Richie Farmer said. “Kentucky had 513 equine cases of West Nile in 2002, the first full year the virus was active in Kentucky, and 137 horses died. Since then, vaccination has become much more common, and the number of cases of West Nile has fallen sharply.”
Rusty Ford, equine programs manager for the Kentucky Office of the State Veterinarian, said not only has the vaccination proven to be effective, it is safe and a simple thing to do in order to keep horses safe from WNV. But the time to get the animals protected has nearly passed.

“We are getting into the time of the season where, if you haven’t vaccinated, you have put your horse at risk,” he said. “Now, you still have an opportunity to vaccinate, but if it is a first-time vaccinate, it takes a little bit of time before the vaccine has an opportunity to stimulate the immune response needed to provide the protection. There is still opportunity to provide protection to your horse.”

Ford added the vaccination for WNV is an annual treatment and encourages horse owners to check with their veterinarians. He also said the opportunity for the disease to be on the increase is elevated because of the number of mosquitoes in the state at this time – and it is not only horses that need to be protected.   

The Centers for Disease Control and Prevention (CDC) notes the “disease is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.”

It is the equine population that takes the brunt of the blow when it comes to animal infestation. According to information from the American Assoc. of Equine Practitioners, horses represent 96.9 percent of all non-human mammalian cases of WNV. The organization also notes WNV is the leading cause of arbovirus encephalitis (inflammation of the brain) in horses and humans in the United States.

Protecting Kentucky’s equine population is a big deal. Information from the Kentucky Equine Education Project (KEEP) indicates the industry represents an estimated $4 billion economic impact on the state’s economy and an $8.8 billion economic impact on the tourism industry, which features the horse industry as its signature promotional attraction.

Mosquitoes out west

The heavy rains experienced this spring brought flooding to many areas, especially in western Kentucky. This set up the perfect scenario for a heavy infestation of mosquitoes.

Grayson Brown, entomologist at the University of Kentucky (UK) College of Agriculture, said of the 59 mosquito species in the state, the vast majority are inland floodwater mosquitoes, which are one of the top two mosquito species that will bite humans, most likely at dusk or right after dark.

“Inland floodwater mosquitoes will bite any ground-dwelling mammal, but they are primarily a nuisance biter. They currently don’t transmit many diseases in Kentucky,” he said. “However, they are a big issue for dog owners because they can transmit canine heartworm.”

Brown also said some areas of western Kentucky are reporting 20 mosquito bites a minute, which is well above treatment thresholds.

The state is chipping in to help combat the infestation by hiring Clarke and Dynamic Aviation to conduct aerial mosquito control applications over more than 700,000 acres in western Kentucky, according to the KDA.
“The flooding has put water in unusual places, such as abandoned houses or the trunks of trees that have fallen over,” Brown said. “We will probably be battling mosquitoes throughout the entire summer.”

The KDA has made recommendations to landowners to help keep mosquito numbers down, including changing water every week in bird baths, pet bowls, wading pools and watering troughs.