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West Nile numbers rise

Charlotte Sun - 12/1/2017

So far this year, 32 sentinel chickens tested positive for West Nile Virus, and four for St. Louis encephalitis, making Sarasota County the second-highest in Florida for disease present in birds, according to the Centers for Disease Control.

Every week since Aug. 8, chickens from flocks in neighborhoods, including Englewood, North Port, Venice, Osprey and Sarasota, have tested positive for disease. The new report shows one diseased chicken in Englewood, three in North Port (including one along Sumter Boulevard) and two in Osprey.

Charlotte County went from one case last year to seven since January.

Manatee County ranks first in the state with 43 cases of West Nile Virus found in sentinel chickens. It also had the first case of locally transmitted Zika in the region.

The CDC also reports Sarasota, Charlotte, Manatee, Hillsborough and Lee counties are under a public health emergency due to imported Zika virus infections.

The Centers for Disease Control tracks sentinel chickens in each county, and shows results in an online weekly arbovirus surveillance report for the public to monitor for disease and health department warnings.

Because so many chickens tested positive for West Nile Virus in Sarasota County on Nov. 3, ?the Florida Department of Health was ordered to advise residents there’s a countywide increase in mosquito-borne disease activity. Sarasota County is only one of four counties in the state under this advisory.

The increase in diseased sentinel chickens is also showing up in Charlotte County where it borders with Sarasota County. Mosquitoes know no county boundaries. Some fly the length of a football field, while others can fly 15 miles, said Scott Schermerhorn, Charlotte County manager of Mosquito and Aquatic Weed Control.

“We have a couple more chickens turn positive associated with the north boundary of Sarasota in North Port and Englewood,” Schermerhorn said. “We are thinking the storm brought some higher populations of mosquitoes that hit the northern part of our counties in Englewood and North Port and upper portions of the Myakka River.

“We have treated those areas once we got the results back that there were chickens with West Nile Virus. We are monitoring to see if anything pops up. We have seen breeding mosquitoes in the ruts made by trucks that are still filled with standing water. We treat it immediately.”

Schermerhorn said there are 24 sentinel flocks monitoring for disease in Charlotte County, including the Charlotte County side of Englewood, Placida, near the El Jobean Bridge, at San Casa Drive area, in Port Charlotte, and the areas off Burnt Store Road and Bermont Road.

“Each time a chicken is found with disease, it is changed out with a fresh chicken that has been vaccinated,” he said.

Schermerhorn generally shuts down the sentinel flock in January and February because temperatures generally dip below 50 degrees and mosquitoes are less active. However, because there’s still presence of West Nile Virus in Charlotte County, he’s leaving the chickens in place to monitor for disease.

“We’ve received complaints in Placida and Little Gasparilla and the Palm Island areas, so we went on a massive larvicide (ditch spraying) campaign to kill the mosquitoes before Thanksgiving,” he said. “We should know the results of the spray campaign. We will be ready if we are hit with another large hatch of mosquitoes.”

32 cases in Sarasota County

Each time West Nile Virus was found in chickens, the situation was monitored, according to Matt Smith, Sarasota County Mosquito Control manager.

In late June, the first case of a dead eagle was reported in Florida that died of West Nile Virus. It was found in the Celery Fields, a rookery owned by Sarasota County, with 266 species of birds. Spray logs show the mosquito control district didn’t do any additional spraying in that neighborhood after the eagle died.

“Fortunately, that species of mosquito does not readily feed on humans, so virus indicated by sentinel chickens does not correlate directly to human threat, but rather gives us a better idea where to focus our resources of surveillance and treatments,” Smith said in a Nov. 21 email to the Sun.

“At this point, mosquito populations are low and the colder weather will begin to inhibit viral growth in mosquito populations. That being said, we do continually monitor for mosquito-borne disease and operate under the general assumption that it is always present in the environment on some level.”

Schermerhorn said the mosquitoes that spread West Nile Virus do infect humans and not just chickens.

“They do bite humans,” he said. “Some species will take a meal, and that will be sufficient. But it depends on how badly they need the protein to lay eggs. If there are a great many mosquitoes in one area, they are going to bite more because there’s only so many resources for them to bite. They will choose humans.”

Email: eallen@sun-herald.com


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