For Immediate Release August 8, 2002

West Nile Virus (WNV) Advances Westward


A horse in Haskell County, about 50 miles north of Abilene, tested positive Wednesday, August 7, for the mosquito-borne disease West Nile Virus (WNV). This is the 21st horse to test positive for WNV in Texas, and is the westernmost detection of the virus in the state.

"Previously, WNV had been detected only as far west as Travis County," reported Dr. Joe Garrett of the Zoonosis Control Division of the Texas Department of Health. "The virus was confirmed in a dead blue jay submitted from southwest Austin on July 17." He noted that infected birds have been found in seven counties: Collin, Dallas, Galveston, Harris, Montgomery, Tarrant and Travis. Infected mosquitoes have been detected in Dallas, Fort Bend, Harris, Orange and Jefferson counties.

"We credit the Texas Department of Health with confirming infection in the Haskell County horse. The private veterinary practitioner, suspecting that the animal might have rabies, submitted the brain to the TDH laboratory, where rabies testing is conducted. After ruling out that disease, health department laboratory technicians tested the tissue for West Nile Virus and confirmed infection," said Dr. Linda Logan, Texas' state veterinarian and executive director for the Texas Animal Health Commission (TAHC), the state's livestock health regulatory agency. She said unless rabies is suspected, WNV testing for horses is usually conducted at the Texas Veterinary Medical Diagnostic Laboratory (TVMDL) at College Station. WNV testing for humans, birds and mosquitoes are conducted by the Texas Department of Health (TDH).

"We're continuing to urge owners to have their horses, donkeys, mules and other equids vaccinated against this form of 'sleeping sickness' which continues to spread westward," said Dr. Linda Logan, Texas' state veterinarian and executive director for the Texas Animal Health Commission (TAHC). "To gain protection against the virus, however, equids need two injections of WNV vaccine administered at least three to six weeks apart. The animal will not develop full immunity for about four to six weeks after the second injection." Dr. Logan advised owners to further protect horses with insect repellents, and if possible, house the animals at night in stalls with screens to prevent contact with potentially infected mosquitoes.

"Likewise, we urge residents to apply insect repellents if they are going to be outside when mosquitoes are active," commented Dr. Joe Garrett of the Zoonosis Control Division of the Texas Department of Health. "There is no vaccine for humans, so disease prevention is our only option. Drain all sources of stagnant water, keep pools optimally chlorinated, and change water in birdbaths daily to prevent mosquitoes from using these sites for breeding grounds. Because some mosquitoes breed in grassy areas, it's also a good idea to keep areas around homes mowed"

Although blue jays, crows and more than 70 other species of birds carry the virus, they do not pose a direct WNV health risk to humans or horses, stressed Dr. Logan. She explained that the disease cycle must involve mosquitoes that feed on the infected birds, then transmit the disease to humans or horses.

"We want receive samples of dead blue jays and crows, particularly from areas west of Houston, so that we can track the progression of this disease as it advances westward," said Dr. Garrett. "For surveillance testing at the Texas Department of Health, we need 'freshly' dead birds that have not begun to decompose. If you have a dead bird to submit, call your local health department, or the state office at 1-512-458-7255 for instructions. If you handle the bird, wear gloves to protect yourself against any possible parasites or other diseases the bird may have contracted, and double-bag the carcass. Prior to laboratory submission, it's best to place the bird in a cool place, such as an ice chest, to slow decomposition."

"WNV will continue to spread, but like the veterinarian in Haskell County, we need always to consider rabies or other diseases, if animals stagger, are unable to rise, or become disoriented," said Dr. Logan. "Although fairly rare, rabies can strike livestock, and if owners handle an animal stricken with the disease, they must receive preventive medical treatment. It's important to have a diagnosis when livestock become extremely sick or die. If your animals are exhibiting signs of neurological distress, notify your veterinary practitioner and TAHC at 1-800-550-8242."

Additional information about WNV can be accessed on the internet at:
http://www.tdh.state.tx.us/zoonosis/diseases/arboviral/westnile/westnile.asp

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