Flood of Equine Encephalitis Cases Follow Hurricane Isaac

Flood of Equine Encephalitis Cases Follow Hurricane Isaac

Gulf State mosquito populations are flourishing in pools of water left in the wake of Hurricane Isaac, resulting in an "inordinate amount of equine deaths attributed to encephalitis," says Louisiana Assistant State Veterinarian Diane Stacy, DVM.

Photo: Erica Larson, News Editor

Gulf State mosquito populations are flourishing in pools of stagnant water left in the wake of Isaac. The result is an "inordinate amount of equine deaths attributed to encephalitis," says Louisiana’s Assistant State Veterinarian Diane Stacy, DVM.

Stacy's office has been flooded with calls reporting horses with neurologic signs and "downer" horses, which can be clinical signs of West Nile Virus (WNV) and Eastern equine encephalitis (EEE). Both EEE and WNV are spread by mosquitoes.
 
"As of today (September 11, 2012) we have had 42 confirmed cases of West Nile and 43 confirmed cases of equine encephalitis reported to our office," said Stacy.
 
The 43 confirmed cases of EEE in Louisiana are almost double the 26 cases reported by the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) as of September 4, 2012.  
 
In 2011, there were three confirmed EEE cases and no cases of WNV in Louisiana.
 
"We are urging horse owners to contact their veterinarians to develop an appropriate vaccination protocol for their horses, or to at least boost against WNV and EEE," Stacy added. 
 
Said Angela M. Pelzel, DVM, a Western regional epidemiologist with APHIS, "the EEE and WEE vaccine is marketed and sold by feed stores (and other outlets) and can be purchased in the U.S. without a prescription, so it is legal for owners to give that vaccine themselves."
 
That said, "Vaccination is preferably done by a veterinarian so that the vaccination can be properly recorded," Pelzel noted. 
 
The reason for this surge of EEE cases is not yet clear. Scott Weese, DVM, DVSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph's Ontario Veterinary College noted, "It's hard to say why EEE has these cycles. Hurricanes help by providing more breeding grounds (flooded areas) for mosquitoes, especially because the main EEE mosquito vectors tend to like brackish water. Beyond that, whether it's changes in cycling in birds or other mosquito factors is hard to say. There are many diseases that have unpredictable trends that occur over years."
 
EEE case numbers can be monitored online through the USDA. 

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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