TDH watching for signs of West Nile virus

A dead bird on the ground is not a sign that captures most people’s immediate attention. But to officials at the Texas Department of Health (TDH), such a situation is high on the list that sparks interest and activates disease surveillance activities. Checking dead birds, especially crows and blue jays, is one of several monitoring systems in place in Texas to detect if West Nile virus is introduced to the state, said Julie Rawlings of TDH’s Infectious Disease Epidemiology and Surveillance Division. Others include testing mosquitoes, maintaining flocks of chickens for testing at strategic sites in the state, working with veterinarians who treat horses and checking tests of people hospitalized with symptoms of encephalitis. The West Nile virus, closely related to both St. Louis enchephalits (SLE) and dengue viruses, was first seen in the United States along the East Coast in 1999. Now the virus has been reported in states ranging from New York and New Hampshire southward to Georgia and Florida. Wild birds are the principal hosts for mosquito-born encephalitis viruses. Mosquitoes feed on infected birds, then transmit the serious, sometimes deadly organisms to humans and animals. These diseases include SLE and West Nile infections along with both western and eastern equine encephalomyelitis. The illness is not spread from person to person or from bird to human. Testing birds that have recently died is critical to the West Nile virus surveillance, Rawlings said. Unlike other encephalitis viruses that do not harm the birds that carry them, West Nile virus is fatal to some species, especially crows and blue jays. “We are asking people to call us when they see freshly dead birds, where it’s not obviously trauma, so the birds can be tested to determine if they are infected with the West Nile virus,” Rawlings said. The phone number in Austin is 512-458-7255. To detect West Nile virus, TDH is concentrating on monitoring mosquito species likely to feed on birds migrating from the northeastern United States through the Gulf Coast. Most of the surveillance will be in the eastern third of the state, generally in counties east of the I-35 corridor. Areas involved in the monitoring system include Chambers, Galveston, Brazoria, Nueces, Klebeg, Kenedy, Cameron and Hidalgo counties. Harris County has its own monitoring system. In addition, testing for West Nile virus is now included in the long-established monitoring programs in Brazoria, Dallas, El Paso, Jefferson, Orange, Lubbock and Wichita Counties. Also, city and county health departments, public health regions, military installations, universities and other local mosquito control programs send specimens to the TDH Laboratory for identification, Rawlings said. Daily during late spring, summer and fall, the TDH Laboratory receives box after box of cylinders filled with dozens of lively mosquitoes. More than 20,000 mosquito specimens are processed by the TDH Lab yearly, each carefully recorded and checked for diseases. It’s a major part of the early warning system for encephalitis, helping prevent human outbreaks. Information from the testing allows local mosquito control personnel to reduce mosquito populations in affected areas before people are exposed. Mild infections of SLE may occur with a fever and headache. West Nile infections are usually mild with flu-like symptoms including fever, headache, sore throat, body aches and fatigue, often with skin rash and swollen lymph glands. More severe infections of both SLE and West Nile may include headache, high fever, neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness and, in rare cases, death. People may reduce their risk of encephalitis by avoiding mosquito bites and reducing mosquito breeding sites, especially by eliminating standing water.

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