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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

Moving forward in the Battle against Aedes aegypti and Dengue in Key West, Florida

On March 15, 2012 the Florida Keys Mosquito Control District (FKMCD) hosted a town hall meeting in Key West to provide information about the use of a novel mosquito control strategy that promises to reduce Aedes aegypti populations. The strategy employs a genetically modified Ae. aegypti strain produced by the company Oxitec. This Ae. aegypti strain contains a genetic factor that causes lethality in any progeny resulting from matings with the strain. The factor functions only in nature in the absence of tetracyline in the larval environment. The presence of tetracycline in the larval laboratory environment is used to suppress the factor in order to be able to rear the strain. The Oxitec claim is that releasing males of this strain into a location like Key West will reduce the fertility of the native female Ae. aegypti that mate with these modified males. By releasing large numbers of these males the expectation is that there will be a reduction in naturally occurring Ae. aegypti with the promise of a corresponding reduction in dengue.

Reducing Ae. aegypti populations with a method that promises to only directly affect Ae. aegypti and might also reduce dengue transmission is certainly laudable. This novel method holds great promise. However there are still many unanswered questions about the technology and as yet there is no precedent on whether the strategy will successfully reduce Ae. aegypti in Key West or reduce the risk for dengue transmission.

The decision to move forward with this new technology in a proposed test of the method in Key West has received a large amount of scrutiny in Key West. The Commissioners of the FKMCD and the FKMCD Director have acted responsibly by calling attention to the potential for the new technique in Key West's battle against Ae. aegypti and dengue, while also proceeding with caution. FKMCD has sought Information about the technology from Oxitec. Oxitec's responses to concerns have been provided to inform the public using the FKMCD web site. In addition to Oxitec, FKMCD also relied on many non-partisan mosquito and vector-borne disease consultants for information. FKMCD has also sought approval for a small scale test of the proposed method from an authoritative state or federal agency. Currently no government agency has claimed any responsibility for issuing approval or a permit. There are yet unanswered concerns about the appropriateness and safety of the technology in Key West. As of April 2012, there are no plans to move forward with a small scale test of the Oxitec strategy in Key West

FKMCD deserves commendations for acting responsibly by opening up the decision-making process to use this technology and by soliciting broad public input and advice. The town hall meeting held on March 15, 2012 illustrated the difficulties, controversy and public concern about using this new technology. The interest and concerns from scientists and the public at large were openly expressed.

Interested readers can read excellent summaries of many of the issues including papers by Eric Hoffman of Friends of the Earth at and by a group at The Max Planck Institute for Evolutionary Biology at

Figure 1. A mosquito-proof rain barrel in Cuba.

What does all this mean for Key West and for Florida mosquito control? I agree with the cautious approach that has been taken in Key West regarding this new technology. However, consider how we might view this same issue should dengue return to Key West with a vengeance. What will be our view of the new technology should dengue virus (DENV) serotype 2,3 or 4 appear in Key West with 500 cases and 10 deaths? Recall that a substantial portion of Key West's citizens were likely infected with DENV-1 during 2009-2010. This prior infection makes these people more susceptible to serious disease upon infection with a second dengue serotype. Should we have been less cautious with the Oxitec proposal? Should Key West take a chance at least a small scale test of the Oxitec method with the chance of reducing Ae. aegypti? Should large scale releases be considered? These are difficult questions.

Figure 1. A mosquito sanitation brigade, Panama 1905.

Note that the Oxitec strategy, though novel and with promise, is not the only strategy that could be used to control Ae. aegypti and reduce dengue transmission. William Gorgas successfully led a huge campaign that essentially eradicated Ae. aegypti and brought an end to yellow fever epidemics in Havana, Cuba in 1901 and later in Panama. How was this accomplished? It was an effective and efficient sanitation campaign designed to destroy every existing Ae. aegypti larval habitat. Figure 1 shows a 1901 version of a mosquito proof rain barrel from the sanitation campaign (From: Le Prince, Joseph A. 1916. Mosquito control in Panama: the eradication of malaria and yellow fever in Cuba and Panama. New York: G.P. Putnam's Sons). Figure 2 shows a fumigation brigade controlling mosquitoes in the Panama Canal Zone in 1905 (from NYPL Digital Library at Is it impossible to use similar sanitation to eliminate Ae. aegypti in Key West in 2012? Is there the necessary will in the residents of Key West to eradicate Ae. aegypti?

One can hardly imagine the cost and difficulties of repeating a Gorgas-style governmental sanitation campaign in modern-day Key West, Florida. Active participation by the public in such a campaign is essential. The Key West community must get behind FKMCD and actively participate in an aggressive community wide Ae. aegypti eradication program.

   Walter J. Tabachnick - Retired, Florida Medical Entomology Laboratory
   Department of Entomology and Nematology
   University of Florida IFAS
   Vero Beach, Florida