West Nile Virus Confirmed in Texas

West Nile virus (WNV) was confirmed June 18 in two dead blue jays found in northwest Houston, Texas. Veterinarians at the Texas Animal Health Commission (TAHC), the state's livestock health regulatory agency, are urging owners of horses, mules, donkeys, and other equids to ensure that their animals have been vaccinated against not only WNV, but also against Eastern and Western Equine Encephalitis (EEE and WEE).

"The introduction of West Nile virus into Texas isn't surprising, as we have monitored the south and eastward migration of the disease since it was first detected in North America in New York in l999. Last year, WNV was reported in 738 equids in 20 states," commented Dr. Terry Conger, TAHC's state veterinary pidemiologist. He explained that staff members from the TAHC and the Texas Department of Health (TDH), which focuses on human health issues, have worked jointly to share laboratory and surveillance information and educational materials about this disease which can be transmitted from infected mosquitoes to humans and equids, causing brain swelling and severe illness. Until l999, WNV was confined to Africa, Europe, Asia, and the Middle East.

Dr. Conger said that the cycle of disease for WNV requires two key players: birds, such as crows, blue jays or hawks, that act as a reservoir for the virus, and mosquitoes that become capable of transmitting disease after they take a blood meal from an infected bird. According to the Centers for Disease Control (CDC) in Atlanta, Georgia, there have been no documented cases of person-to-person, animal-to-person or animal-to-animal transmission of WNV. "We consider humans and equids to be 'dead-end' hosts, because they can become ill but haven't been shown to spread infection.

"Late last summer, infected birds were detected in Louisiana and Arkansas," said Dr. Conger.  "Now with the confirmation of infected birds in our state, the Texas Department of Health will probably find infected mosquitoes through their surveillance activities.

"Vaccines are available to protect horses, mules and donkeys against WNV and other 'sleeping sicknesses,' but the shots are no value if they aren't given prior to disease exposure," said Dr. Conger. "We are running out of time before we may see disease transmission, so get your equids vaccinated now. The vaccines require two doses, administered three to six weeks apart, and full protection doesn't develop until four to six weeks after the second dose. Realistically, then, it can seven to 12 weeks for the horse to develop maximum resistance to infection. That's why it's so important to start the round of vaccinations now."

Dr Conger reminded equid owners that an annual booster is required for continued protection of the animals.

"If your horse or other equid has signs of illness, such as staggering or an inability to rise, call your veterinarian immediately. It also is extremely important to rule out other causes of sickness with similar signs, such as rabies," asserted Dr. Conger. "If it is WNV, appropriate care must be provided quickly. Historically, about 20 percent of infected equids either died or had to be euthanized due to their illness."

"To help reduce the possibility of WNV transmission, don't give mosquitoes a place to breed," said Dr. Conger.  "Keep only fresh water in birdbaths and troughs and maintain optimal chlorination in swimming pools. Drain any flowerpots or other containers that hold stagnant water and keep roof gutters clean. Control puddles that collect around stables."

Dr. Conger commended the TDH on its WNV disease surveillance, which includes testing mosquitoes, dead crows, blue jays, hawks and sampling zoo birds. He said "freshly" dead crows, blue jays or hawks can be submitted for laboratory examination, by calling the nearest regional Texas Department of Health office or the Texas Department of Health in Austin at 512/458-7255.

"Always wear gloves when handling a dead bird, and wash your hands thoroughly afterward," warned Dr. Conger. "The bird could have had parasites or other illnesses, and precautions are always advisable when handling animals that have died of unknown causes."

Dr. Conger reminded livestock owners that, as always, the TAHC operates a 24-hour hotline for taking reports of unusual signs in livestock, including:

  1. staggering, falling, or inability to rise
  2. illness affecting a large percentage of animals
  3. sudden death loss
  4. blistering around an animal's lips, teats or hooves
  5. unusual ticks or maggots

"We are always on guard, watching for a potential foreign animal disease, so we ask producers and veterinarians to watch for these signs and report them immediately to us at 1-800-550-8242," said Dr. Conger. "Immediate response is our best defense in the case of any dangerous disease."

Additional information about WNV in Texas can be accessed on the Internet at: http://www.tdh.state.tx.us/zoonosis/diseases/arboviral/westnile/westnile.aspx. More information about WNV can be found at our West Nile Virus topic center.

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