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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

The Challenge of West Nile Virus to Florida Mosquito Control

As the summer of 2000 approaches, we come closer to resolving the "big question" everyone has been asking this winter. Will West Nile (WN) virus appear in the U. S. again? Florida is certainly at risk for the appearance of WN virus. After all, Florida has experienced outbreaks of WN's near relative St. Louis encephalitis (SLE) virus. Accordingly, many Florida readers of Buzz Words have been preparing for a possible WN introduction. Our citizens and visitors to Florida should take some comfort in these efforts and preparations. The challenges to Florida Mosquito Control to prepare and protect Florida from WN virus are many. Two issues have been critical in preparedness plans. The first is surveillance for WN virus to ensure it is detected as early as possible. The second is to coordinate the appropriate mosquito control and public health responses so that Florida citizens are protected against infection, and to reduce the impact of the virus on our citizens and the economy of the state.

Surveillance for WN in Florida, as well as SLE, rely on an early warning system to detect these viruses in sentinel chickens located in likely virus transmission zones, based on previous SLE history. In addition, wildlife agencies have arranged for the testing of wild birds that exhibit WN-like clinical signs. If, as expected, WN follows patterns similar to SLE, it is unlikely that Florida will be surprised by human cases prior to detection of the viruses in sentinel chickens and/or wild birds. It is likely that infections in wild birds or horses may be detected by wildlife agencies or veterinarians in those regions of Florida lacking active arboviral surveillance programs. It is a safe bet that Florida will not be surprised as was New York City during the summer of 1999.

The challenge to Florida Mosquito Control will then be to address the second issue: the development of appropriate control responses to protect citizens and reduce the impact of the virus once it is detected. It is here that the expertise of Florida Mosquito Control, and the Florida Department of Health's previous experience with SLE, will be vital to our success. Mosquito control will first be challenged to identify the Florida vector of WN virus. As a first step, most consider Culex nigripalpus as the most likely target in view of its proven role as an SLE vector. Hence initial control strategies are likely to follow the SLE-Cx. nigripalpus model for which there is ample precedence in Florida. Mosquito control may have to alter control techniques should other species, such as Cx. quinquefasciatus, be incriminated in WN transmission. Here the long-standing cooperation between the Florida Mosquito Control Districts, the FMEL and PHEREC will pay great dividends in providing information for decision-making. FMEL will provide updates and analyses of WN data in Florida through its Encephalitis Information System web page at During SLE outbreaks, Florida Mosquito Control and the Florida Department of Health have used data analyses to provide recommendations to the public for personal protection measures. This will be done for WN.

If WN virus is detected in Florida, the challenge for Florida Mosquito Control, will be to provide control that is effective, cost efficient, and proper. We still do not know nearly enough about the epidemiology, hosts, and vectors of SLE and possibly WN in Florida to provide optimal protection and control. There is much to do. More information and research by the Florida research laboratories are critical. However, Florida is fortunate to have large segments of the state that are covered by well-run, local, experienced, and established mosquito control agencies. This strength, so obviously absent in the 1999 outbreak in NY and CT, will greatly mitigate the impact of WN and SLE epidemics. With the forewarning provided by the Florida surveillance system, the appropriate responses by Mosquito Control Districts and the Department of Health, and the involvement of an educated public able to understand and take personal protection measures, Florida citizens will have another healthy summer, regardless of the appearance of WN virus. With continued research, mosquito control will become more effective, efficient and proper.

Walter J. Tabachnick - Retired
Florida Medical Entomology Laboratory