With West Nile in 8 towns, Warren County urges mosquito-borne disease prevention

Warren County health officials are warning residents about the potential dangers of mosquito-borne diseases, highlighting several illnesses that can affect both humans and animals in the region.

Pesticide treatment to control adult mosquito populations is scheduled for Thursday night in Mansfield Township, where a sample of mosquitoes collected recently tested positive for West Nile virus, officials said.

While these and other mosquito samples have tested positive, there have been no confirmed human cases of West Nile in Warren County this year.

The Mansfield specimens, collected Aug. 11 near the Morris Canal, represent the 11th sample to test positive for the virus among 277 total collections in Warren County as of Thursday.

Additional positive results were returned this summer in Belvidere plus the townships of Franklin, Harmony, Hope, Knowlton, Lopatcong and Washington, officials said. Engineers are conducting treatments to control mosquito populations at these and other sites with standing bodies of water throughout the county.

Thursday’s treatment is scheduled for 7:45–11:30 p.m. in the Port Murray area of Mansfield, along Main Street, Towpath Road, Hoffman Road and Cherry Tree Bend Road, according to the Warren County Mosquito Commission.

As of Aug. 14, there were 506 recorded samples of mosquitoes to test positive for the West Nile virus in New Jersey.

West Nile virus remains the most common mosquito-transmitted disease in the area, primarily affecting birds but capable of spreading to humans and horses. The virus typically causes mild symptoms in humans, though severe cases can lead to encephalitis or meningitis.

St. Louis encephalitis, another mosquito-borne threat in Warren County, shares similar symptoms with West Nile. The disease primarily circulates between birds and mosquitoes but can infect humans through mosquito bites.

Local health authorities also monitor for Eastern equine encephalitis (EEE), a rare but serious viral disease. While EEE primarily affects horses, human cases can occur and often result in severe illness with a high mortality rate.

The county’s mosquito control program tracks La Crosse encephalitis as well, which mainly affects children under 16 years old. This virus, transmitted by tree-hole breeding mosquitoes, can cause severe neuroinvasive disease.

Dog heartworm disease, spread by infected mosquitoes, poses a significant threat to canines in the region. The parasitic worms can cause severe damage to dogs’ hearts and blood vessels if left untreated.

Health officials emphasize the importance of prevention, including eliminating standing water around homes and using appropriate insect repellents during outdoor activities.

Contrary to common misconceptions, mosquitoes cannot transmit all viruses — including HIV, which doesn’t survive in mosquitoes.

Mosquito-borne virus transmission typically involves complex cycles between birds and mosquitoes. EEE, for example, circulates between birds via the Culiseta melanura mosquito species. When mosquito populations surge, the virus can amplify in bird populations before being transmitted to mammals through “bridge vector” mosquitoes that feed on both birds and mammals.

Most people (80%) infected with West Nile virus do not develop symptoms, according to the U.S. Centers for Disease Control and Prevention; less than 1% of people infected develop severe illness that affects the central nervous system, requires hospitalization or results in death.

First discovered in Uganda in 1937, West Nile appeared in North America in 1999. While no human cases were documented in New Jersey that year, the virus was found in 73 dead crows and mosquito samples. Crows are particularly vulnerable, while introduced species like European starlings show natural immunity.

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Glenn Epps can be reached at [email protected] or at glenn_epps_ on Instagram, Facebook and Threads.