Health officials issue mosquito-borne illness advisory

A spike in mosquito-borne West Nile Virus has prompted a health advisory in Pinellas County, as officials enhance efforts to eradicate the blood-sucking pests. 

Pinellas County Mosquito Control’s sentinel chickens were the first to sound the alarm. Flocks in Oldsmar and east Tarpon Springs have tested positive for West Nile Virus (WNV), which was also detected in Pasco and Hillsborough Counties. 

The Florida Department of Health issued a mosquito-borne illness advisory Aug. 27 due to increased activity and is urging residents to take additional precautions. There are no vaccines or specific treatments for WNV, and symptoms range from mild to severe.

Caroline Pickart is an environmental specialist and director of outreach and education for Pinellas County Mosquito Control. She said her department has recently increased treatments, including additional truck fogging, aerial larviciding and ground inspections to mitigate breeding areas.

“The big thing with the advisories and the alerts is it’s really to inform our residents and the public of what we’re seeing,” Pickart told the Catalyst. “There’s different criteria for what makes a county go into an advisory and into an alert. We recently went to our advisory because we had multiple sentinel chickens test positive for the virus.” 

The Florida Department of Health (FDOH) had no reports of human infections in the week ending Aug. 23, the most recently available data, and just one case throughout 2025. Pickart said her department typically sees an uptick in WNV around this time of year. 

Pinellas is home to over 40 mosquito species that need just a bottle cap full of water to lay eggs. While all are nearly unavoidable nuisances, 17 can also pose serious health risks. 

The rainy season makes it easier for mosquitoes to flourish. However, Pickart credited migratory birds that began entering the area in August for helping spread WNV. 

“Sometimes we have an infected mosquito decide it’s going to bite a person or a horse instead of another bird, and that’s how those diseases can spill over into those populations,” she added. “That’s why we have programs like our sentinel chicken program.”

Mosquitoes and birds typically transmit WNV, Eastern Equine Encephalitis and St. Louis Encephalitis. Chickens are also an attractive meal, do not experience illnesses and cannot transmit viruses to uninfected mosquitoes, making them an ideal first line of defense. 

Mosquito control operates eight sentinel chicken coops strategically placed throughout the county. The FDOH tests weekly blood samples for the presence of antibodies, and results inform the county’s plan of attack. 

“They’re working exactly as they should,” Pickart said of the chickens. 

Sentinel chickens continuously receive food, water, treats and toys for the roughly six months they are kept in coops, or until they test positive for a mosquito-borne illness. Photo: Pinellas County Government.

Most people infected with WNV do not show any symptoms. Some develop mild, flu-like illnesses, although fatigue and weakness can persist for weeks or months. 

However, some people, particularly those with chronic medical conditions or weakened immune systems, can develop a severe illness that can result in hospitalization or death. The Centers for Disease Control (CDC) advises anyone experiencing high fevers, neck stiffness, muscle weakness, confusion or tremors to consult a doctor. 

Pickart and her team implore residents to follow the “3D’s:” Dress in light-colored, long-sleeved clothing with closed shoes; defend yourself by using insect repellent with CDC-recommended ingredients, including DEET, Picaridin, IR3535 or Oil of Lemon Eucalyptus; and dump or cover any standing water around homes. 

“These diseases can happen year-round here in Florida,” Pickart said. “Even though we’re seeing an increase right now of West Nile, that doesn’t mean there’s never not a chance of it being present.” 

She noted that each mosquito species has a preferred habitat, which includes urban areas. Pickart said “quite a few” prefer manmade containers, “and those are actually the mosquitoes we’re concerned about.” 

The county operates 58 mosquito traps to catch and identify adults. Officials use collected data to conduct overnight fogging treatments and have increased those efforts around sentinel chicken coops in affected areas. 

Helicopters drop granular larvicide around difficult-to-reach and vast breeding habitats. Concerned residents throughout unincorporated Pinellas and its 24 municipalities can request free treatments. 

“We service the entire county,” Pickart said. “And then our technicians will also do routine inspections.” 

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