Mosquito-Transmitted Diseases Back on Rise

by TN Press Release Center on August 25, 2012

Press release from the Tennessee Department of Health; August 24, 2012: 

NASHVILLE, Tenn. – Tennessee’s Department of Health and Department of Agriculture are urging Tennesseans, including horse owners and veterinarians, to be on the alert for the re-emergence of viruses transmitted by mosquitoes. As many states are experiencing one of the largest outbreaks of West Nile virus in recent years, Tennessee is beginning to see cases in humans and horses. In Tennessee, most human WNV cases occur in August and September, and so far this summer, there have been six human cases reported in the state.

“The risk for West Nile virus transmission is high in Tennessee, particularly in Shelby County,” said State Medical Entomologist Abelardo Moncayo, PhD. “The best way to protect yourself is to prevent mosquito bites, and there are simple precautions we can all take to reduce our contact with mosquitoes and our risk of bites.”

Health officials identified WNV-positive pools of mosquitoes in Tennessee locations in the first week of May, much earlier than in a typical summer. Currently, in Shelby County in August, 60 percent of mosquito pools submitted for testing have been positive for West Nile virus.

Mosquitoes become infected with WNV by feeding on infected birds and can transmit the virus to humans and other animals, such as horses, through their bites. Most human WNV infections cause no noticeable symptoms. However, about 20 percent of infections result in symptoms that may include fever, headache and body aches. Occasionally more severe symptoms occur, and in less than one percent of human cases, WNV may cause a life-threatening infection of the brain. Certain populations are at higher risk including the elderly, persons who abuse alcohol and those with chronic health conditions such as diabetes, hypertension, renal disease and cardiovascular disease.

The Tennessee Department of Agriculture is encouraging horse owners to protect their horses by reviewing records and getting their animals vaccinated for mosquito-borne diseases including West Nile virus. TDA recently confirmed its first case of WNV infection in a Tennessee horse this year.

“Outbreaks of viral encephalitis in horses are a seasonal occurrence due to the prevalence of mosquitoes in late summer and early fall,” said State Veterinarian Charles Hatcher, DVM. “Horse owners should be aware of symptoms of viral encephalitis and consult their local veterinarian for preventive measures like vaccinations or if their horse develops any of the signs associated with this group of diseases.”

Although humans cannot contract viral encephalitis directly from infected horses, viral encephalitis does pose a public health risk and residents are reminded to take proper precautions.

“Since there is no WNV vaccine available for humans, people should avoid mosquito bites by using insect repellants containing DEET, Picaridin, Oil of Lemon Eucalyptus or IR3535 from dusk to dawn,” Moncayo said. “People should remember to report dead crows and blue jays to their local health department so they can be tested for West Nile virus. This is the best way to know if active transmission is occurring in your area.”

Human and animal health officials say mosquito control is very important for disease prevention. Mosquito control should include removal of all man-made potential sources of stagnant water that may allow mosquitoes to breed including discarded tires, containers left outdoors or clogged roof gutters. Insect repellants can be used on horses but with limited value. Screened stalls can also help reduce exposure to animals.

The Department of Agriculture’s Kord Diagnostic Laboratory in Nashville provides services for livestock owners and private veterinarians. For more information about WNV or other viral diseases in horses, contact the Tennessee Department of Agriculture, State Veterinarian office and diagnostic laboratory at (615) 837-5120.

More information on West Nile virus is available on the Department of Health website at http://health.state.tn.us/ceds/WNV/wnvhome.asp.

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