West Nile Virus Activity Could Pick Up Soon In Texas

Writer: Edith Chenault, (979) 845-2886, email: e-chenault1@tamu.edu
Contact: Dr. Jim Olson, (979) 845-5037

COLLEGE STATION -- A Texas mosquito expert is anticipating another, and earlier, round of
West Nile virus for this state.

West Nile encephalitis activity has already picked up in Louisiana with the virus reportedly being found in
birds throughout the state and in the mosquito population around Baton Rouge, said Dr. Jim Olson,
entomologist with the Texas Agricultural Experiment Station.

“With that being an indication, we could be in for another year of West Nile virus activity,” in Texas, Olson
said. “This is probably one of the earliest records of a mosquito-borne virus (becoming active) in the South.”

Normally, activity begins in May or June, he said.

In 2002, the first year West Nile was reported in Texas, approximately 202 laboratory-positive human cases
and 13 deaths in the state were attributed to the virus, according to the Centers for Disease Control and
Prevention.

According to the CDC, West Nile virus is commonly found in Africa, West Asia and the Middle East. It is
closely related to the St. Louis encephalitis virus, and it can infect humans, birds, mosquitoes, horses and
some other mammals.

West Nile fever is usually a mild disease in people and is characterized by flu-like symptoms –– it typically
lasts only a few days and does not appear to cause any long-term health effects, the CDC said.

Olson said West Nile virus is bird-borne; to date, more than 110 species of birds have been found to be
infected with and have the ability to serve as the source of the virus.

“Mosquitos feeding on infected birds become infected themselves and then pass that on to other birds,” he
said. “Or if, by chance, if they feed on horses and humans, they could infect those.”

State health officials are still encouraging horse and mule owners to vaccinate their animals. If the animals
were vaccinated last year, a booster is recommended, Olson said.

“Consult your veterinarian and get them vaccinated now,” he said. “There is a delay time from when the
vaccination starts and when the horses will build a high enough immunity to be considered protected. That
delay time can be up to six weeks.”

For people to avoid mosquitos and the possibility of disease, the entomologist recommended
the three P's:

  • Protection of self, using protective clothing and a repellent of choice and avoiding being outside
  during the times of day when mosquitos are active.

Olson suggested wearing clothing that is loose-fitting. "With tight-fitting clothing, mosquitos can drill right
through the fabric," he said.

Long-sleeved and long-legged clothing provides protection for skin. Clothing should be light-colored because
mosquitos are attracted to darker hues, he said.

  • Prevent mosquito breeding around the house by removing all sources of standing water, dumping
  artificial containers and removing those containers.

  • Prevent mosquitos from getting into homes with the proper screening and sealing frames doors and
  windows. Olson said he suspected most human infections of West Nile and other encephalitis
  viruses are caused by bites either in the home or places close by, such as yards and patios.

Citronella candles offer some protection outside if they are used in areas with little wind movement, but
Olson urged people to practice safety when burning those.

Insect-killing devices, such as the “bug zappers” should be placed at a distance -- about 50 feet -- from the
area you're trying to protect. “They do tend to attract more mosquitos than they kill,” he said.

Community-wide spraying can be effective if done properly, he said.
 
“Any spraying that is done needs to be based on need, as indicated by the presence of mosquitos and, even
more so, the presence of the virus in that area,” Olson explained.

Proper surveillance by health authorities can determine those two factors.

“Indiscriminate spraying of mosquitos that is not out of a sense of need is not recommended. There has to be
an actual need. Otherwise, other measures are sufficient,” he said.  Further information is available from:
http://www.cdc.gov/ncidod/dvbid/westnile/