The Program targets mosquito species known to be primary vectors of encephalitis viruses recognized in Texas and that produce disease in humans. Based on past experiences with mosquito-borne encephalitis in Texas, Culex quinquefasciatus and Culex tarsalis are the important vectors for West Nile, St. Louis encephalitis, and western equine encephalitis viruses. Culiseta melanura is the known enzootic vector of eastern equine encephalitis virus (EEE); however, Aedes, Coquillettidia, Anopheles, and Culex species may be bridge vectors and transmit EEE virus to both humans and horses. The tree-hole mosquito Ae. triseriatus is the primary vector for La Crosse virus. In 2002, West Nile virus (WN) was first detected in wild birds collected in Houston, Texas. WN virus has been isolated from Cx. quinquefasciatus, Cx. salinarius, Cx. (Melanoconion) sp, Cx. restuans, Cx. tarsalis, Cx. nigripalpus, Ae. albopictus, Ae. taeniorhynchus, and Ps. columbiae.
Mosquito specimens are submitted to the DSHS from numerous Texas city and county health departments, health service regions, military installations, universities, and local mosquito control programs. Specific information on field surveillance techniques is available at this site. At the Laboratory, the mosquitoes are identified to species, pooled, and tested for the presence of arboviruses. Whenever the laboratory isolates one of these viruses, laboratory personnel notify the agency that submitted the specimens and the appropriate HSR, as well as the Zoonosis Control Branch. The responsible HSR will work with the submitting agency to help assess any health threats and determine what mosquito control measures need to be initiated based on the virus detected.