A Proven Record of Protecting the Public's Health...

The goal of VDCI's mosquito-borne disease surveillance programs is to detect mosquito-borne viruses in local bird and mosquito populations before sufficient amplification of virus can occur. After virus is detected, management practices can be discussed and implemented thereby reducing the number of infected mosquitoes and simultaneously reducing the risk of human transmission.

Mosquito Surveillance

Typically, mosquito-borne viruses can first be detected in bird populations, followed by detection in mosquitoes after the virus has had the opportunity to establish itself locally in birds. The most important potential mosquito-borne diseases in most areas of the country are St. Louis Encephalitis (SLE), West Nile virus (WNV), LaCrosse Encephalitis (LAC) Western Equine Encephalitis (WEE) and Eastern Equine Encephalitis (EEE). Of primary concern is the recent introduction of WNV. The principle mosquito species involved in the transmission of WNV are those in the genus Culex, especially Cx. pipiens, Cx. quinquefasciatus, Cx. restuans and Cx. tarsalis. These mosquitoes are very abundant in urban areas because the larvae live in water with a high organic content, such as sewer drains, catch basins, retention basins, settling lagoons, and similar areas. Therefore, separating these mosquitoes from others in collections is important for purposes of surveillance and monitoring. Mosquito pools can then tested for WNV with the new Rapid Analyte Measurement Platform (RAMP) bioassay which provides timely and accurate identification of WNV-infected mosquito pools for increased response capability.

Avian Surveillance

Detection of transmission of arboviruses in bird populations can be accomplished using caged chickens as sentinels and bleeding them routinely to detect viral antibodies (seroconversions). Frequent bleeding of carefully placed flocks of sentinel chickens can provide a very sensitive and cost-effective method to monitor both WNV and SLE activity. Because chickens are continuously available to host-seeking mosquitoes, they are usually exposed to more mosquitoes than can be collected by trapping, especially when adult mosquito abundance is low.

Virus activity in the wild bird population also can be monitored by mist netting birds and testing their blood for evidence of infection. Young (hatching year) birds can be used to detect virus infection from the current year. Similarly, once captured, birds can be banded and upon recapture it can be determined if the prevalence of the virus in the region has changed over time. Wild bird sampling is not often used due to the expenses involved, its technically difficult, and relatively labor intensive in comparison to other surveillance methods. In addition, it is often difficult to relate wild bird data a specific location because the actual location where a free-flying bird became infected is rarely known.

Response to Mosquito-borne Diseases

Contact with local health agencies should be maintained during the mosquito control season. In addition, regular contact should be maintained with state and federal health agencies in order to project possible regional health concerns. Any finding of local significance is then immediately reported to the proper municipal official in addition to the routine reporting.

VDCI works closely with municipalities and all other appropriate agencies to implement the appropriate response to all findings of mosquito-borne diseases within our programs. The presence of mosquito-borne pathogens within an area should result in one or more responses or interventions by VDCI after consultation and discussion with all appropriate officials.

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Larval Surveillance• Adult Surveillance• Disease Monitoring