Breakthrough comes in preventing Dengue fever

  • Published
  • By Senior Airman Erin M. Peterson
  • 59th Medical Wing Public Affairs
LACKLAND AIR FORCE BASE, Texas (AFPN) --  Dengue fever and the potentially fatal form of the disease, dengue hemorrhagic fever, are rated by the Department of Defense as number 3 of the top 40 disease threats to deployed military forces. 

According to a report from the Pan American Health Organization, an international public health agency, over the past 20 years the occurrence of Dengue in sub-tropical regions of the Americas has shown an increasing trend and 2007 was an epidemic year.

Dengue outbreaks have been reported in Honduras, Costa Rica and Mexico. In 2008, the disease is epidemic in Brazil, and Dengue fever is recognized as an emerging infectious disease globally to include the continental United State.

Dengue fever is a communicable disease manifested by an abrupt onset of fever, with severe headache, muscle and joint pains and rashes. A second infection may result in the much more severe dengue hemorrhagic fever. It has a geographical distribution comparable to malaria.

No cure exists for the disease; the treatment is supportive therapy. Prevention and control of dengue virus transmission are essential because in the absence of a vaccine or preventative drug, the only means of protecting deployed military personnel is by preventing the bites from infected mosquitoes.

Many factors relate directly to the outbreak of Dengue fever. Chief among them is improperly disposing of tires, cans and bottles, particularly plastic bottles, These objects can catch rain water and remain in an environment for a long time without degrading, creating breeding grounds for Aedes aegypti, the species of mosquito responsible for transmitting the Dengue virus.

Aedes aegypti lay their eggs in small, dark, shaded water containers where no wind exists. The overabundance of these containers in the environment increases the probability of Dengue infection through the bite of the mosquitoes.

Dengue fever has become a greater concern as military members continue to deploy to those locations where the Aedes aegypti are likely to be found. Efficacious force health protection technologies are required to protect the war fighter.
Air Force entomologist Col. James Swaby and molecular biologist James McAvin, both from the 59th Medical Wing at Lackland Air Force Base, Texas, recognized the need to rapidly identify the locations where Dengue-carrying mosquitoes are prominent and dispose of the threat to America's warfighters.

Working for years, they developed genetic tests for both the virus and the mosquito that can be used on a rugged, field deployable instrument, and methods to freeze-dry the assays to enable testing in the most austere settings. From that point, they were able to test for the specific species and virus in any environment.

Previously, in order to determine whether Aedes aegypti were present, entomologists would place small, black plastic jars, called Ovatraps, containing the ideal environment for the mosquito to lay eggs in the environment.

The entomologist then would collect the eggs from the Ovatraps and send them to a lab where they would raise them until they were adult mosquitoes, after which the species could be identified by a highly-skilled entomologist using a high-powered microscope. This process took weeks and made it improbable that the infected mosquitoes had remained in the same area. The presence of the virus in the mosquitoes could only be determined by incubating samples from the mosquitoes for several days in one of only a few laboratories equipped and staffed to do this highly specialized work.

Colonel Swaby and Mr. McAvin wanted to disprove the assumption that genetic-based testing in an unstructured, non-lab, austere field environment was not possible.

Discovering that freeze-drying the assays needed for the tests was possible, they were able to refute this assumption by identifying the mosquito and whether it was infected with the Dengue virus in the field in just minutes. This hastened the process and made eliminating the infected mosquitoes in a specific area more effective by concentrating control measures only in areas where the Aedes aegypti are infected with the virus, and in a matter of minutes.

"For the first time our Dengue assay has received DOD certification for environmental surveillance," said Colonel Swaby. "From this extensive research, the stage is set to launch more effective and timely control measures to protect our fighting forces from the debilitating effects of this disease." 

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