Mosquito Season and West Nile Virus in Horses

PetMD Editorial
Published: April 24, 2018
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As mosquito season approaches, the Nevada Department of Agriculture is strongly urging horse owners to vaccinate their horses against West Nile virus (WNV) and take the proper precautions to control mosquito populations.

Rutgers New Jersey Agricultural Experiment Station’s FAQs on the West Nile virus say that the West Nile virus begins to appear in the spring, and it will steadily increase as we enter the summer season. The infection rates in mosquitoes and birds tends to peak during late summer and early fall, so that is when horses are the most susceptible to transmission.

Rutgers also explains that the West Nile virus is actually a disease found in wild avian populations. It is spread and maintained by mosquitoes that feed on the blood of infected birds. Those mosquitoes, in turn, become carriers of the disease and can spread it to humans and horses through a bite.

According to the press release from the Nevada Department of Agriculture, Dr. JJ Goicoechea, veterinarian for the NDA, explains, “Vaccination is the best protection horse owners have for their animals.” He says, “Vaccinations, in conjunction with practices that reduce exposure to mosquitoes, are very effective in protecting horses from WNV.”

As explained by Rutgers, “Birds circulate high levels of the pathogen in their blood and serve as the sole source of the virus for mosquitoes … West Nile virus cannot be spread directly from horse to horse or from horse to human. A mosquito that has previously fed on an infected bird is required in all cases.” states that the best way to protect your horses is through horse vaccines and mosquito prevention methods. For horses who have previously received a West Nile virus vaccine, only an annual booster shot will be needed. If a horse has no vaccination history, then it will need a two-shot vaccination series during a three- to six-week period.

Other precautions that are recommended to help prevent West Nile virus in horses are measures to reduce the mosquito populations and possible breeding areas. suggests removing stagnant water sources, using fans in stable areas to hinder a mosquito’s ability to access the horses, and applying equine-approved mosquito repellents.

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Read more: West Nile Virus