West Nile Virus detected in chickens in New Castle

By Rachel Sawicki
Posted 7/27/21

DOVER — Delaware’s Division of Natural Resources and Environmental Control detected West Nile Virus for the first time this year in a sample of sentinel chickens in northern New Castle …

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West Nile Virus detected in chickens in New Castle


DOVER — The mosquitoes are biting, and they are bringing the annual spate of problems with them.

Delaware’s Division of Natural Resources and Environmental Control detected West Nile Virus for the first time this year in a sample of sentinel chickens in northern New Castle County on July 19.

“This first finding is a good outreach opportunity for us to remind the public to take personal protection measures to avoid or reduce mosquito bites and also to practice good water sanitation on their properties to reduce mosquito populations,” said William Meredith, program administrator for Delaware’s Mosquito Control Section.

The transmission period for WNV and Eastern Equine Encephalitis, another virus passed by mosquitoes, is typically in August and September, so Mr. Meredith said detection in late July is expected.

Only 20% of humans exhibit symptoms, such as fever, body and muscle aches, headache, nausea, vomiting and rash, or get severely ill if they contract WNV. A smaller number of people can develop serious illnesses involving neurological problems, paralysis and possibly death.

EEE is not as prevalent as WNV, but can present more severe symptoms in humans and horses. Infections in horses are fatal in 70% to 90% of EEE cases and in 30% of WNV cases.

DNREC has 20 stations across the state with sentinel chickens that are sampled on a weekly basis for WNV. The chickens quickly develop antibodies that prevent them from getting sick, which makes them great subjects to track the virus, Mr. Meredith said. There are also 30 other stations throughout the state for tracking general mosquito populations.

Virus pathogens are normal among wild bird populations, but Mr. Meredith said the issue is when those pathogens jump from a bird to a horse or a human.

“There are certain types of mosquitoes that are capable of doing that type of transmission, from a wild bird to a human or a horse,” he said. “Sentinel chickens are a good indicator because they’re down on the ground where people are. Up in the canopy, the virus can run around undetected.”

Population and virus detection give the MCS a “two-prong approach,” to help them determine where action is needed not only for public comfort, but also to protect public health.

“Certainly a lot of our local businesses and local economies don’t want to see huge mosquito infestations, but it gets worse when you combine that with the potential for disease transmission,” Mr. Meredith said.

He said that this year is fairly normal in terms of mosquito intensity.

Every year they take various precautions and control measures to control mosquito populations. Mr. Meredith notes that Delaware is in the top 10 states with the greatest percentage of wetlands. The state is also in the top 10 for greatest population density.

“Our human population density and high percent wetlands makes it a challenge for mosquito control in comparison to a lot of other areas around the country and it just has to do with our natural setting,” Mr. Meredith said. “People in Delaware demand, expect and need mosquito relief.”

MCS first tries to target mosquitoes at the source.

“We’d like to get into the aquatic habitats where the eggs are laid and the larvae are reared and focus our effort there, because then mosquito problems are more concentrated,” Mr. Meredith said. “We’re not trying to spray all Delaware to eliminate mosquitoes, we want to focus on where they come from, and we use order management practices where we’re able to do that, involving altering, say, wetlands habitats.”

While they cover population control in bigger areas, DNREC reminds the community to also take common-sense precautions to avoid mosquito bites, like wearing long-sleeved shirts and long pants when outdoors in mosquito-prone areas, applying insect repellent and avoiding mosquito-infested areas and times of peak mosquito activity around dusk, dawn and at night.

The state veterinarian within the Department of Agriculture urges horse owners to contact their veterinarians as soon as possible to have horses and other equines vaccinated against WNV and EEE. Neither disease has a specific drug treatment.