West Nile Virus is Here!

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West Nile Virus is Here!

I was thinking of doing a West Nile Virus blog but thought it may be just a little early to be thinking of mosquitoes. But I decided to look around to find some “be prepared” tips for the warmer weather. I was shocked when I saw the map on Pennsylvania’s official West Nile Virus website with a county in red, which indicates a positive West Nile virus detection because this is MARCH! Then I found the March 29, 2012 press release:

First Veterinary Positive for West Nile Virus in 2012

The West Nile Virus program is reporting the euthanization of a horse due to an active case of West Nile in Northampton County. This case heralds the arrival of West Nile Virus in 2012 and is the earliest report of a horse illness since the disease reached Pennsylvania in 2000. This case also serves as a reminder to vaccinate horses against West Nile Virus. Program staff will conduct surveillance and necessary control measures to reduce the risk of further WNV transmission. The WNV program will begin the full-time monitoring, controlling and testing of mosquitoes in April. Collection and testing of dead birds begins May 1 and can be reported on www.westnile.state.pa.us or by calling (717) 346-8238.

  • Contact: Kevin Sunday, Pennsylvania Department of Environmental Protection, at 717-787-1323 or kesunday@pa.gov

What is West Nile Virus?

This virus can cause encephalitis and is commonly found in humans, birds, and other vertebrates. West Nile virus is transmitted by infected mosquitoes, which become infected after biting infected wild birds, the primary hosts of the virus. West Nile virus was first detected in the United States in August 1999 in New York City. In that year, 62 people (with 7 deaths) and 25 horses (which 9 died or were put down) were diagnosed with West Nile encephalitis. In addition, zoo birds and native bird species, especially crows, were affected by the virus. For the next several years, more and more states were reporting incidents of West Nile virus in both humans and animals until it reached California.

How is West Nile Virus Transmitted?

The virus circulates and multiplies for several days in a mosquito’s blood before penetrating its salivary glands. After an incubation of 3 to 15 days, an infected mosquito can transmit the virus to both humans and animals while feeding on them. Fortunately, even in areas where mosquitoes do carry the virus, very few mosquitoes are infected. So, the chance of being bitten by an infected mosquito is small. Furthermore, of those who become infected, less than 1 percent will develop a severe illness. Remember that most people who get infected do not develop any disease at all.

Horse Vaccine Information

A human vaccine is not available at this time, but researchers are working on one. However, several horse vaccines are available that have met the USDA requirements for safety. Horse owners should strongly consider vaccinating their horses. Consult with your veterinarian for the most up-to-date information and research on available vaccines and recommendations for use. Remember, that horses vaccinated against eastern equine encephalitis, western equine encephalitis, and Venezuelan equine encephalitis will not be protected against a West Nile virus infection.

Prevention and Control

To reduce the likelihood of exposure to mosquitoes, horse owners should implement the following pest management practices:

  • Keep horses stabled during peak periods of mosquito activity (dusk and dawn).
  • Fans may reduce the ability of mosquitoes to feed on horses.
  • Avoid turning on lights inside the stable during the evening and overnight. Mosquitoes are attracted to incandescent bulbs. Fluorescent lights neither attract nor repel mosquitoes.
  • Place incandescent bulbs about 50 yards from the stable to attract mosquitoes away from the horses. Black lights are of little value as attractants for mosquitoes.
  • Prohibit pigeons and other birds from roosting and living in or near the stables.
  • Periodically examine the property for dead birds, particularly crows, blue jays, and raptors (hawks and owls). Report any suspicious deaths to the Pennsylvania Department of Health at 1-877-PAHEALTH. Handle dead birds only if wearing protective gloves, and place birds in tied plastic bags.
  • Carefully examine your property and eliminate locations that could serve as breeding grounds for mosquitoes. Shallow stagnant or standing water, used tires, clogged roof gutters, and manure storage pits are ideal places for mosquitoes to breed.
  • Clean water troughs once a week and pay attention to puddles that form around and under the troughs. Consider using stone or landscaping to reduce or eliminate hoof prints, where mosquitoes might breed.
  • Topical preparations containing mosquito repellents are available for horses. Read the label before using the product, and follow all instructions.
  • Stable premises can be fogged in the evening to reduce the number of mosquitoes.
  • Do not allow water to stagnate in bird baths, wading pools, wheelbarrows, ornamental pools, water gardens, and swimming pools and their covers.

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