Plenty of rain, plenty of mosquitoes, and more related illness

A wet winter and spring throughout Florida resulted in more cases of mosquito-borne viruses being transmitted to sentinel chickens, horses and humans over the summer within the state.

As a result, University of Florida entomology professor Jonathan Day is urging those engaging in outdoor activities this fall to stay protected from potential bug bites.

Infected mosquitoes transmitting the eastern equine encephalitis virus (EEEV) and West Nile virus (WNV) throughout Florida are capable of causing severe disease in humans and horses. To date, three human cases of EEEV have been reported in Florida, including one each in Columbia County and Taylor County. Seven human cases of the West Nile Virus have been reported in Bay, Nassau, Duval and Manatee counties.

Day said in most instances, infected humans who were interviewed were camping and failed to wear bug repellent.

“Know that if you are going camping in North Florida and Alachua County, the risk is pretty high, and then avoid mosquitoes,” Day said. “Do everything you can to avoid mosquitoes, protective clothing, avoiding mosquito activity periods and repellents would be the way to go.”

While most people infected with EEEV have no apparent illness, severe cases can begin with the sudden onset of headache, high fever, chills or vomiting, that can progress to disorientation, seizures or coma. In West Nile cases, there is no vaccine available and treatment after infection is only supportive. About one in five  people infected develop a fever and other symptoms, while one in 150 people develop a serious, sometimes fatal illness.

Day said environmental factors have played a role in the higher number of mosquito-borne virus cases, including heavy rainfall. From January through the end of August, 43.83 inches of rain had been recorded at Gainesville Regional Airport, above the normal rainfall average of 34.76 inches.

“We have had a lot of rain this year and that really favors the dispersal of infected mosquitoes and the transmission of the eastern virus,” Day said.

Day said that while EEEV horse cases and human cases peak during July and August, cases of West Nile Virus transmission are more common in September and October.

“While the real threat of eastern transmission is probably decreasing, the threat of West Nile transmission is increasing,” Day said.

Many Florida mosquito control and public health programs use sentinel chickens to monitor mosquito-borne virus transmission. As of Aug. 29, 139 sentinel chickens in 12 Florida counties have tested positive for the EEEV antibody. Most cases are in Florida, specifically from Orange to Nassau counties. During that same timeframe, 165 sentinel chickens in 15 Florida counties tested positive for West Nile, ranging from Walton County in the Florida Panhandle to Charlotte County along the Florida Gulf Coast.

Fifty-one cases of Eastern Equine Encephalitis have been reported in horses in North Florida, and most have died. One West Nile Virus case has been reported in a horse in Levy County.