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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

West Nile in Florida: Getting Ready for 2002

The arrival of West Nile (WN) virus in Florida in 2001 tested the ability of Florida mosquito control, State, regional and local agencies to meet public expectations to reduce risk from WN. Many Florida agencies responded and many individuals worked tirelessly through the summer. All should be commended for their efforts.

We must begin to evaluate what the impact of Florida's actions was on WN in Florida, and to make improvements. It is essential that we prepare for WN in 2002 now. Here I consider only actions related to Florida Mosquito Control.

In considering the impact of mosquito control, a presentation by Dr. Maurice W. Provost, of the Florida State Board of Health (and later the first Director of the FMEL) made nearly 50 years ago is still relevant. I call your attention to excerpts from Dr. Provost's presentation.

"Mosquito Control Is Not Just Another Kind of Insect Control"

"Mosquito control is not just another kind of insect control; it is by all odds the most complicated and difficult of all forms of insect control... it calls for a large amount of very specialized mosquito biology and highly specific control techniques. ...I would like to leave you with this simple message: there is an enormous and costly gap between what we know about the business of controlling mosquitoes in Florida and what we should know.

People judge mosquito control by one criterion only: effectiveness. If mosquitoes are bad, control is bad or else there isn't enough of it; if mosquitoes are not bad control is good. The whys and wherefores of mosquito abundance are not their concern. But the custodians of public monies must judge mosquito control by more criteria than just effectiveness. We must consider the efficiency of the methods. We must consider the wisdom of using certain techniques, the possibilities of damaging land values and natural resources, the proper appraisal of health involvement's and many other concerns. In short, mosquito control must be judged on a cost and consequence basis. It is only fair that the public be told that mosquito control cannot long be efficient and proper, let alone effective, without the backing of a research program.

Mosquito control as practiced in many parts of Florida today is not very efficient and much of it is of doubtful propriety. This is not a reflection on anyone concerned with the direction of control, but rather on the prevailing ignorance of mosquito biology. There is just too much we do not know about mosquitoes and their environment. All the inefficiency and impropriety can be blamed squarely on the lag of research behind operation.

...Florida has such an enormous mosquito potential that there will probably always be a need for killing mosquitoes that are on the wing. There is a huge amount of adulticiding being done right now in Florida. In some counties it is the primary method of mosquito control being carried on. is precisely here that inefficiency is primarily because we know so little of the adult life of mosquitoes and especially their movements. The need for biological research is surely as urgent as it is obvious.

... I would like to advise against the planning an expansion of mosquito control in Florida on the assumption that we know all the answers now. We certainly do not, as this past summer's experience should abundantly prove. This State needs more mosquito control, yes, but it also needs more efficient and more properly channeled mosquito control. There is no way in the world of knowing more than by learning. And learning in this case means mosquito research."

M. W. Provost, Miami Kiwanis Club Presentation, Dec. 7, 1951.

Florida did its best with the little information in hand about WN in Florida's ecosystem. Can we do better next time? Can we meet Dr. Provost's challenge to provide effective, efficient and environmentally proper mosquito control.

Florida mosquito control is effective, efficient and proper in many locations. When there is information on local mosquito biology, surveillance and baseline experience, then the appropriate methods have achieved defined objectives. These methods are reviewed in the Florida Mosquito Control White Paper. However, mosquito control professionals also know when specific strategies are neither effective, efficient nor proper.

Almost any Florida mosquito control professional can relate stories of ineffective control. For example, Florida Culex nigripalpus populations pose a tremendous challenge when burgeoning populations are difficult to impact through larviciding or source reduction. Florida Districts also report that adulticiding with Dibrom may have little effect on C. nigripalpus populations despite significant reductions of other pests, i.e., Aedes and Ochlerotatus. It is essential that well planned and critically evaluated research programs are developed to control C. nigripalpus. We also need information on the effectiveness of strategies to control Florida Culex quinquefasciatus. I hope the reader will connect the thread - these are culprits for WN transmission, and SLE as well. We must have scientifically evaluated control methods. We must critically assess and improve the impact of the 2001 Florida mosquito control in North Florida. Was it effective? efficient? proper?

Dr. Bruce Eldridge (Strategies for surveillance, prevention, and control of arbovirus diseases in western North America. Amer. J. Trop. Med. Hyg. 37 (3): 77S-86S. 1987.) concluded that "the many variables which must be considered in conducting emergency adulticiding, and the studies which have demonstrated that it is very difficult to lower density of vectors to levels below that needed to stop transmissions emphasize that such spraying should be regarded as a remedy to be used only after all preventive measures have failed. Well organized mosquito abatement efforts which include adequate routine sampling for density, vector competence, virus infection, and insecticide susceptibility, are far more effective and, in the long run, more economical."

Where is information going to come from to improve mosquito control? Emergency mosquito control, likely of questionable effectiveness, efficiency and propriety is a poor investment for Florida's resources. Florida must invest in research that will develop appropriate and targeted mosquito and disease control that will have a demonstrated impact on WN, SLE, EEE and other Florida mosquito borne pathogens. This will mean critically peer reviewed, well-planned, organized research efforts with clear, obtainable objectives and defined timetables. There is a lot to learn about WN, SLE and EEE ecology in Florida. I have outlined in previous Buzzword columns, what is needed to move beyond "detection" of WN, which has been a primary focus at this point, to predict and mitigate risk of WN in humans. We must prepare for 2002, for 2003 and beyond. I hope readers will share their thoughts and suggestions with me on these important issues.

Walter J. Tabachnick, - Retired
Florida Medical Entomology Laboratory