West Nile found in mosquitoes in Madison County

(Posted Sept. 6, 2017)

Madison County Public Health has discovered mosquitoes testing positive for the West Nile Virus (WNV). The positive sample was collected on July 31 from the northwest side of London in Madison County. Public Health received notification of the positive sample from the Ohio Department of Health on Aug. 31.

According to Madison County Public Health Commissioner Chris Cook, there have been no confirmed human cases of West Nile Virus in Madison County this year. He also said the discovery of WNV-carrying mosquitoes in Ohio is common.

“As of the end of August, 58 counties in Ohio have trapped and submitted mosquitoes for testing. Of those 58 counties, 33 including Madison had at least one mosquito pool test positive for WNV,” Cook reported.

Ohio Department of Health data shows that a total of 1,299 mosquito pools have tested positive for WNV this year.

“When you look at this kind of data, it is pretty evident that WNV can be found in mosquitoes all across Ohio,” Cook said. “Whether it’s spring, summer or fall, when we give advice to the public, we operate under the assumption that mosquitoes are carrying any number of encephalitis-causing illnesses that can make people sick. We continue to encourage people to wear insect repellent and take steps to protect themselves and their families.”

West Nile Virus is an arbovirus that was first discovered in the United States in 1999. WNV is most commonly spread by infected mosquitoes that can lead to severe fever, encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord).

The most common mosquito in Ohio, the northern house mosquito, or Culex pipiens, carries WNV. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the virus to humans and other animals when they bite.

London Mayor Patrick Closser said his staff will be doing additional mosquito spraying.

“I am committed to working with Public Health to help protect the citizens of and visitors to the city of London,” Closser said. “We are going to do some extra spraying to help knock down the adult mosquito population.”

There has been one confirmed human case of West Nile Virus in Ohio this year. That case occurred in Clermont County. Approximately 80 percent of people who are infected with WNV will not show any symptoms at all. There is no way to know in advance if a person will develop an illness.

Those who develop symptoms usually do so between three and 14 days after they are bitten by the infected mosquito. About 20 percent of people experience mild symptoms of WNV. Mild symptoms include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for a few days to as long as several weeks.

About one in 150 people infected with WNV will develop severe illness. Severe symptoms can include high fever, headache, neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks and the neurological effects may be permanent. There is no specific treatment for WNV infection and care is based on symptoms.

Cook reports that many species of mosquitoes are most active from dusk to dawn, however, some species will bite during the day as well.

“We want people to stay active outside, especially during nice weather,” Cook says.

He encourages everyone to use insect repellents.

“Approved repellents are the most effective line of defense against WNV and mosquito bites,” he said.

When outdoors, use approved repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol (PMD). It is important to follow the directions on the package for reapplication. Repellents that claim to be all-natural or made of essential oils or devices that you wear have not been proven to be effective.

Other measures that can help to reduce risk include:

  • removing standing water from items such as birdbaths, pet dishes, old tires, wading pools, buckets, and toys in the yard;
  • using screens on windows and doors and repairing holes in screens;
  • wearing long-sleeved shirts and long pants, especially in the evening; and
  • placing mosquito netting over baby carriers and strollers.

For more information about West Nile Virus or mosquito control, contact Madison County Public Health at (740) 852-3065 or at info@madisonpublichealth.org.

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