West Nile Virus Moves Westward, Page 2

Horse Talk

West Nile Virus Moves Westward (continued) -- Page 2

Since birds are the carriers of WNV, many states, such as California, are setting up "sentinel flocks"...flocks of chickens located throughout the state that are monitored for illness and death. Plus, California and other states are tracking dead crow sightings.

Crows die from an infection of WNV. Consequently, most state health departments are asking individuals to report dead crows or dead crow sightings. Some areas will collect the dead birds, and they will be tested. Other areas are simply "tracking" sightings. Knowing where and how many dead crows there are within a county helps to forecast the human risk for West Nile Virus...and its spread pattern.

There is no evidence that WNV is spread directly from dead birds to humans or horses. But never handle a dead bird...or any dead animal...with bare hands.

Since some horse owners are also dog owners, a dog or even a cat may become ill from WNV. They become infected the same way as humans and horses...by the bite of an infected mosquito. The virus is located in the mosquito's salivary glands. During blood feeding, the mosquito becomes infected when it feeds on infected birds that may circulate the virus in their blood for a few days. But even if a dog or cat has WNV, there is no documented evidence of person-to-person transmission.

Horses also become infected with WNV by the bite if infected mosquitoes. While data suggests that most horses infected with WNV recover, there are deaths.

According to the Animal and Plant Health Inspection Service (APHIS) of the United States Department of Agriculture (USDA), 60 horses were confirmed with WNV in 2000. Of the 60 horses, 37 survived and 23 (38 percent) died or were euthanized. The horses ranged in age from four months to 38 years, with an average age of 14 years. Thirty-six cases were male; 24 female. Onset of the illness in the horses was from mid-August to the end of October.

According to the October 2001 issue of Horse Report from the UC-Davis Center for Equine Health, "This year (2001) so far, 81 horses have been affected in at least 20 states, with a 33-per-cent fatality rate."

One of the biggest myths circulating among horse owners is that if a horse is vaccinated against Eastern Encephalitis (EEE), Western Equine Encephalitis (WEE), or Venezuelan Equine Encephalitis (VEE)... the horse will not "catch" the WNV. This is false! EEE, WEE and VEE belong to another family of viruses for which there is no cross-protection. So even if a horse is vaccinated against EEE, WEE and/or VEE, it could still become infected with WNV.

If a horse does become infected with the virus, there is no reason to destroy the animal just because it is infected. An infected horse cannot "spread" the disease to its owner or to another horse. Although no antibiotics or antiviral drugs have yet been identified as effective treatments for WNV infections, supportive and consistent standard veterinary practice data suggest most horses recover from the infection.

On August 1, 2001, the USDA granted a "conditional approval" to Fort Dodge Animal Health for an inactivated (killed) equine vaccine against the WNV. But some veterinarians are "unsure" how it will work, and "its effectiveness is unknown", plus some individual state regulations are still pending. So, for the individual horse owner who wants to vaccinate a horse, the first course of action is to contact your personal equine veterinarian. If your vet has no information about the vaccine, the next step would be to contact your individual state veterinarian for comment and advice. If that fails, contact Fort Dodge directly for their information and help.

Meantime, prevention is the best course of action. Since mosquitoes are the "bridge vector", mosquito control is vital! Some states have set up surveillance programs to monitor for WNV. Others have begun mosquito testing for infected "pools", placed out "sentinel chicken" flocks, encephalitis surveillance, and dead bird testing. States with major flyways for bird migration, such as the Tulelake area in southern Oregon and northern California, are especially concerned with dead bird testing. In other areas, counties and cities have started plans for mosquito spraying.

But the average horse owner can help to control mosquitoes with some good old common sense:

Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers.
Remove all discarded or old tires on your property. Used tires have become the most important source of mosquito breeding in the nation.
Drill holes in the bottoms of recycling containers kept outside. The holes will allow water to drain out.
Make sure roof gutters drain properly, and clean clogged gutters. A standing tablespoon of water can support a "pool" of mosquitoes
Change the water in bird-baths at least twice a week.
In a water trough, have a slight overflow to keep the water moving. Add a couple of fish...fish east mosquito eggs...and turn upside down all water containers not being used in corrals, paddocks or fields.
When turning water containers upside down, don't forget to turn that wheelbarrow over and those water pails, too!
Clean vegetation and debris from pond edges. Standing water with a high organic content, such as leaves, grass or other plant material, is a prime location for mosquito breeding.
Clean and chlorinate swimming pools, outdoor saunas and hot tubs, and drain water from pool covers.
Use landscaping to eliminate standing water that collects on your property.

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Bonnie Davis is a Bay Area resident, free lance writer and horsecamping/trail riding advocate with over 30 years experience. Her stories, articles, and columns have been published in national and international publications such as Western Horseman, Paint Horse Journal, Horse & Horseman, Quarter Horse Journal, Western Side (Italy), Cascade Horseman, California Horse Review, Performance Horse Review, and San Jose Mercury News. Bonnie was a featured speaker at Horsexpo in Sacramento in '99, '00 and '01.