Bumper crop of mosquitoes increases West Nile Virus risk

Bumper crop of mosquitoes increases West Nile Virus risk

Horse owners need to vaccinate animals, take measures to reduce mosquito population to ward off diseases

The extremely wet weather in late April through May resulted in flooding in June and filled ponds and reservoirs.

It also provided thousands of spots of standing water around barns, home, pastures and ditches -- perfect breeding grounds for a bumper crop of mosquitoes.

That bumper crop is reaching peak activity across the United States as we enter peak season, July through October.

That means that horses are now at their highest risk of contracting West Nile Virus and cases have already been documented this year.

West Nile is a life-threatening disease that originates in birds but can be transmitted by mosquitoes which feed on infected birds to horses, humans and other mammals.

PROTECT NOW: A bumper crop of mosquitoes means elevated danger from West Nile Virus and horse owners are reminded to protect their animals with vaccinations and measures to prevent the breeding grounds for mosquito populations.

The Centers for Disease Control and Prevention, as of January, 2015, reported numbers of infections in the U.S. as 19,623 cases in all species.

In humans, the virus is often mild, with symptoms no worse than the common cold and many individuals don't even know that have contracted it. In some cases, however, it can cause life-threatening illness similar to encephalitis.

Zoetis Equine News reports that vaccination remains the most effective way to protect horses against all mosquito-borne diseases, including Eastern equine encephalitis, Western equine encephalitis and West Nile.

Zoetis is the manufacturer of the first vaccine on the market after West Nile struck, West Nile Innovator.

Researchers recently tested horses’ responses to six West Nile virus vaccination regimens and found some substantial differences in their immune responses. While all of the vaccinated horses demonstrated an initial immune response, by Day 28, the antibody titer response of the horses vaccinated with West Nile Innovator was four times higher than those vaccinated with the one-dose, big combination WNV-containing vaccines.

“We thought West-Nile Innovator would produce a higher immune response than the large one-dose combination West Nile vaccines, but we did not think it would be nearly four times higher,” said Kevin G. Hankins, DVM, senior veterinarian, Equine Veterinary Operations, Zoetis.

West Nile is a core vaccination requirement, along with vaccinations for EEE, WEE, tetanus and rabies, according to the American Association of Equine Practitioners guidelines.

For horses that have not been vaccinated or are overdue for vaccination, it’s not too late to help protect them against this life-threatening disease. West Nile Innovator and a combination of other booster vaccines can help provide added protection horses need to stay healthy.

“We have a disease that is here to stay with an effective vaccine but no treatment in the case of infection,” Dr. Hankins said. “That makes vaccination a cheap insurance policy.”

In conjunction with vaccination, good management techniques can help prevent West Nile cases. Techniques include:

?         Destroying any mosquito breeding habitats by removing all potential sources of stagnant water

?         Cleaning and emptying any water-holding containers, such as water buckets, water troughs and plastic containers, on a weekly basis6

?         Applying insect repellents or bringing horses inside during peak mosquito feeding hours between dusk and dawn

Remember, West Nile does not always lead to signs of illness. In horses that do become clinically ill, the virus infects the central nervous system and may cause symptoms such as loss of appetite and depression. Other clinical signs may include fever, weakness or paralysis of hind limbs, impaired vision, ataxia, aimless wandering, walking in circles, hyperexcitability or coma.7 If horse owners notice signs or symptoms of WNV infection in their horses, they should contact a veterinarian immediately, especially if horses are exhibiting neurological signs. The case fatality rate for horses exhibiting clinical signs of West Nile infection is approximately 1 in 3 horses.5

By providing proper vaccination and mosquito population management, horse owners can do their part to help prevent West Nile infections. 

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