Katrina Increases Mosquito Population

Katrina Increases Mosquito Population; WNV Outbreak Not Expected

The mosquito population of the Hurricane Katrina-affected areas is expected to increase at a staggering rate, according to Joe Conlon, American Mosquito Control Association (AMCA) technical advisor. However, he added the possibility of a West Nile virus (WNV) epidemic is unlikely.

"We are not looking for a spike in WNV, or Eastern equine encephalitis (EEE) cases, but we have been wrong before," Conlon said. "Horse owners should be prudent and vaccinate or booster animals in Louisiana, Alabama, and Mississippi."

William Jeter, DVM, bureau chief, Florida Bureau of Animal Disease Control, agrees that a dramatic increase in encephalitis cases might not occur. "The mosquito population will be up, but there are several other factors that must be present along with an increase in mosquito populations in order for outbreaks to. However, there is always an increased risk of equine encephalitic diseases when mosquito populations increase," Jeter said.

Many horses in the area have already developed immunity toward the virus by being exposed naturally or being vaccinated, according to Jeter. Young and unvaccinated horses are at the greatest risk of infection, along with horses that are stressed and have suppressed immune systems.

"Horses have been going for two to three weeks with little to no food or water, and stress levels are very high," Jeter said. Vaccinating unprotected horses now will not hurt them, but under such stressful conditions the effectiveness of the vaccine is questionable and he recommends owners consult their local veterinarians.

Jeter said he is more concerned about an increase in EEE cases. "The mortality rate of horses with West Nile in Florida has been 20-25%. It is important to note that Florida reported very few cases of WNV last year after having dealt with several major hurricane events and this year only one case has been reported. The mortality rate in horses with EEE is 70-90%," he explained.

He recommends using spray repellents to reduce the risk of mosquito infestation. The Center for Disease Control and Prevention (CDC) approved two repellents this year not containing DEET, the gold standard of insect repellents. The two other repellents--Picaridin (KBR 3023) and plant-based oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)]--were found to offer protection similar to repellents with low concentrations of DEET when tested against mosquitoes normally found in the United States. Any type of repellent should be used in strict accordance to the products label. For more information on repellents visit: www.CDC.gov and www.deetonline.org

The Air Force Reserve Command web site stated that two aircraft from the 910th Airlift Wing based in Youngstown, Ohio, were deployed Sept. 8 to fly aerial insecticide spray missions in Louisiana, Mississippi, and Alabama. The aircraft, each capable of spraying 60,000 acres daily, will concentrate on spraying New Orleans before moving to other affected areas.

During Hurricane Hugo (1989), AMCA workers used large Buffalo Turbines (like giant leaf blowers) to eliminate stacks of garbage and debris, perfect breeding habitat for mosquitoes. Once the waters recede following Hurricane Katrina, Conlon believes similar methods will be used in affected areas.

While the risk of a WNV outbreak still looms in the long term, experts believe the biggest threat will be the exponential growth in the mosquito population, which will be an overwhelming nuisance to humans and animals.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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