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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

Chikungunya and Dengue: Challenges for Florida Mosquito Control

Just when you thought it was safe out there, along comes Chikungunya! [see Tabachnick, W. J. 2006. BuzzWords. 6(3): 8-9]. In that earlier article, I introduced the readership to the potential danger to Florida from the mosquito-borne Chikungunya virus (CHIKV). Recall that CHIKV caused an enormous outbreak in the Indian Ocean area in 2006 with millions of cases distributed through the region on several Indian Ocean Islands, reaching as far as India. The symptoms of Chikungunya are unpleasant and include painful inflammation of the joints that result in a stooped posture, fever (>104°F), headache, vomiting, nausea and a skin rash. The symptoms can easily be confused with Dengue. Although symptoms subside within 3-5 days, joint pain can persist for many months or even years after the other symptoms have subsided. The FMCA should take some delight that my statement in the earlier column "The vectors unfortunately, and this should send a chill through U. S. mosquito control and public health workers, are Aedes aegypti and Aedes albopictus" was picked up and quoted in several newspapers, including the Chicago Tribune. So yes, the FMCA Newsletter indeed is being widely read.


Figure 1. Aedes aegypti female
Photo by: James M Newman (FMEL)


Figure 2. Aedes albopictus female
Photo by: Sean McCann (FMEL)

The challenge for Florida mosquito control is to prepare now for a potential Ae. aegypti (Fig. 1) or Ae. albopictus (Fig. 2) borne outbreak, whether it be from CHIKV or just as likely Florida's old nemesis, Dengue virus (DENV). At the recent FMCA Dodd Short Course, Florida mosquito control district Directors discussed the challenges to mitigating an Ae. aegypti or Ae. albopictus borne outbreak using their current mosquito control operations and with current staff levels. Florida and the rest of the U. S. have made great strides predicting West Nile through surveillance and then mitigating potential outbreaks in advance through mosquito control and public education. Pinellas County Mosquito Control's response to West Nile in 2005 is a perfect example (Tabachnick, W. J. and Day, J.F. 2005. West Nile surveillance and Florida Mosquito Control: Acting on surveillance information. BuzzWords, Newsletter of the FMCA. 6(5): 6-8). Much of our knowledge about West Nile in Florida stems from Florida's prior experiences with St. Louis Encephalitis virus (SLEV). Recall that both of these viruses circulate in mosquito to bird cycles permitting opportunities for surveillance and for mitigation to reduce the number of infective vector mosquitoes and, in so doing, reduce the risk of virus transmission to humans. Not so for DENV and CHIKV. These are largely human to mosquito amplification and transmission cycles. The vectors Ae. albopictus and Ae. aegypti can utilize the smallest containers to complete larval development. Aedes albopictus in particular is able to utilize an array of both natural and artificial containers. There are enormous challenges for controlling these mosquitoes. Just look at the difficulties in controlling Ae. aegypti in places like San Juan, Puerto Rico.

Family: Togoviridae
Genus: Alphavirus
Species: Chikungunya virus

The word chikungunya is derived from the Makonde root verb kungunyala, meaning to dry up or become contorted. In India, the disease is known as Aakyda, meaning "stiff man" and Maakyda meaning "monkeylike". These words refer to the arthritic condition that occurs in some patients which causes a stooped posture.

The important point for CHIKV and DENV is that our current SLEV and WNV paradigms for surveillance and for control will not work. This is the time for Florida Mosquito Control to begin to prepare for the potential arrival and subsequent transmission of either DENV or CHIKV. What information should mosquito control collect now to assess potential risk from a reported human case due to either of these viruses? Certainly a start would be to have information on Ae. aegypti and/or Ae. albopictus populations, where they are produced and hot spots with large populations that could be easily targeted for control. What can or should a mosquito control district do to control these populations? There is a great deal of information and experience clearly demonstrating that effective Ae. aegypti and Ae. albopictus control must involve public support and public participation to effectively reduce larval habitats. It would be wise to have plans already in place on how to utilize citizens for these important surveillance and control efforts.

Thankfully we do have some information on Florida Ae. aegypti and Ae. albopictus populations largely due to the long term efforts of FMEL scientists like Phil Lounibos and George O'Meara. They have been studying the interactions between the Ae. aegypti and Ae. albopictus in Florida, and they have collected information on their vector ability for DENV. We have some information on the Florida distributions of these important mosquito species in a broad sense, as well as information on their likely habitat preferences. Certainly, we need to expand and refine this information, particularly habitat preferences, to include more of Florida. Dr. Chris Mores is obtaining information on Florida's Ae. aegypti and Ae. albopictus vector ability for CHIKV. We need to move forward with this work so we can target control strategies, including source reduction, to maximize where it will be most effective.

I urge Florida's mosquito control and public health professionals to begin making plans for an expected case of dengue or Chikungunya in their District or jurisdiction. The questions that we will be asked by the public and media will be the same questions we were asked about WNV in 2001 and 2002. Is there a risk of more cases? Is there a risk of a large outbreak? What will/can mosquito control do to mitigate the risk of a major epidemic? What public health statements need to be issued?

We will begin addressing these issues just as we did for West Nile virus. The UF, IFAS, FMEL will be posting information on dengue and Chikungunya on its website to assist in formulating plans. Dr. Ken Linthicum, Director of the USDA, ARS, Center for Medical and Veterinary Entomology (CMAVE) and I will host a symposium for the FMCA Fall meeting to explore these issues. The FMEL will plan for a workshop on DENV and CHIKV for mosquito control and public health professionals after soliciting interest in such a workshop from Florida mosquito control Directors. Stay tuned to BuzzWords for further information. We have to continue to work together to meet these new challenges.

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