West Nile Virus Found in Four Mosquitoes This Year in Darien

Alvesgaspar Mosquito Picture

Picture by user Alvesgaspar on Wikimedia Commons. Caption there: "A female mosquito of the Culicidae family (Culiseta longiareolata). Size: about 10mm length"

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West Nile Virus has been found in four mosquitoes trapped in Darien this year, the town Health Department says.

[Updated at 4:32 p.m., Wednesday, Aug. 5, with comments from town Health Director David Knauf. Updated 3:48 p.m., Thursday, with latest information from the state Agricultural Experiment Station’s “Mosquito Trapping and Testing Report” for Aug. 6. Updated again at 4:29 p.m., Thursday with information from the experiment station.]

The Health Department adds that there are no reports of Darien residents with the virus, but it urges residents to eliminate places where standing rain water or other standing water might provide a breeding ground for mosquitoes — like clogged roof gutters or even boat covers where rainwater collects.

“The reality is, for what it’s worth, it’s here and it comes back every year,” Darien Health Director David Knauf said of West Nile Virus. There’s no reason to think that Darien is riskier than anywhere else, he said in an interview Wednesday.

“Every year we get positive mosquito results [for West Nile Virus], so enjoy the summer — just remember that it’s just another one of those realities that we live with,” along with deer ticks, sun burn and leaving food out too long in warm conditions, he said.

The Health Department has a slew of ideas about reducing the likelihood that mosquitos will breed around your home — see the bottom of this article for the full list within the department’s announcement.

West Nile Virus also has been found in other communities in Connecticut, including Stamford, New Haven and Guilford. In Stamford, one or more mosquitos that tested positive for the virus was found at Cove Island Park, across Holly Pond from Weed Beach in Darien, on Tuesday, July 28. Fifty mosquitos were trapped and tested at Cove Island Park that day, with the virus found in one or some.

The latest online “Mosquito Trapping and Testing Report” of the Connecticut Agricultural Experiment Station notes that mosquitos this past week were trapped at High School Lane and Brush Island Road (just north of Weed Beach Park and on Holly Pond — this map shows where the road is — the marker or pointer does NOT indicate anything in particular, much less where the mosquito or mosquitos were found).

The report Web page did not have information on testing results in Darien or most other communities tested in the past week (as of 11:46 a.m. on Wednesday).

UPDATE, THURSDAY: As of 3:47 p.m., Thursday, the Mosquito Trapping and Testing Report noted that 100 mosquitos were trapped July 29 at the Brush Island Road station, where West Nile Virus was found.

Last year, mosquitos with West Nile were found in 15 communities in Connecticut, including Darien.

UPDATE, THURSDAY, 4:29 p.m.:

“The number of infected mosquitoes and the number of affected towns is increasing” Dr. Philip Armstrong, Medical Entomologist at the Connecticut Agricultural Experiment Station in a news release. “We expect to see further build-up of West Nile virus in mosquitoes with increased risk of human infection over the rest of the summer and into early fall.”

“Historically in Connecticut August and September are the months when risk of West Nile virus infection is greatest,” Dr. Theodore Andreadis, for the Center for Vector Biology & Zoonotic Diseases at the experiment station, said in the same news release. “We encourage everyone to take steps to prevent mosquito bites, such as using insect repellent and covering bare skin, especially during dusk and dawn when biting mosquitoes are most active.”

The state experiment station maintains a network of 91 mosquito-trapping stations in 72 municipalities in Connectyicut. Every 10 days, on a rotating vbasis, mosquito traps are set Monday through Thursday nights, according to the news release.

Mosquitoes are grouped (pooled) for testing according to species, collection site, and date, the news release said.

Here’s the full Darien Health Department news release: West-Nile-Virus-Update-August-2015.doc.txt

Monitoring program

Alvesgaspar Mosquito Picture

Picture by user Alvesgaspar on Wikimedia Commons. Caption there: “A female mosquito of the Culicidae family (Culiseta longiareolata). Size: about 10mm length”

The s Mosquito Management Program started monitoring mosquitos for diseases on June 4 in a program that lasts through October. The program, coordinated by the Connecticut Agricultural Experiment Station, checks for viruses that can make people ill, including West Nile virus (WNV) and Eastern equine encephalitis virus (EEE).

Monitoring for WNV emphasizes mosquito trapping and testing results,” the health Department said in its announcement. “The CAES maintains a network of 91 mosquito-trapping stations in 72 municipalities throughout the state. Mosquito traps are set Monday – Thursday nights with trapping conducted at each site every ten days on a rotating basis.

“Mosquitoes are grouped (pooled) for testing according to species, collection site, and date. Test results are available approximately one week after mosquito collection and are reported to local health departments.”

The Health Department adds: “[T]here has never been a documented human case of EEE in Connecticut, but the virus is found in birds and bird-biting mosquitoes that live near wetland habitats along the eastern seaboard from New England to Florida.”

Health Department’s Tips for Reducing Mosquitos

In the following excerpt from the announcement, the Darien Health Department gives these tips on avoiding mosquitos and keeping them from breeding near you:

One of the easiest and surest ways to manage mosquitoes around the home is to eliminate standing water where mosquitoes can lay eggs. Mosquitoes need at least 7-10 days in water to fully develop. Some common sources of mosquitoes around the home are:

  • Artificial containers that hold water (e.g., pails, paint cans, discarded tires)
  • Boat or pool covers or tarps that collect rainwater
  • Unmaintained bird baths or wading pools
  • Rain barrels and clogged roof gutters
  • Rot holes in trees and stumps

Practice good sanitation around the home. Homeowners should properly dispose of or recycle trash which can hold rainwater.

Make it a practice to flush bird baths and wading pools weekly. Swimming pool filtering systems should be maintained and in good working order.

Abandoned pools should be drained, filled or “shocked” with pool chemicals. Openings for standing water sources, such as rain barrels, can be sealed or covered with screening.

Rotten stumps and tree holes can be filled with sand. Discarded tires should be disposed of properly, holes (0.5 inches or larger) can be drilled in the bottom of the tires to drain rainwater or the tires can be stacked and covered to prevent rainwater from entering. 

Ornamental pools and aquatic gardens can become sources of mosquitoes if the water is allowed to stagnate. Water should be changed frequently or an aerator can be installed.

Homeowners can practice their own biological control by stocking minnows, such as Gambusia, koi or guppies, which will eat mosquito larvae. The fish will need to be brought indoors for the winter or restocked annually because they will not survive Connecticut winters.

Large pond stocking with non-native fish or releasing fish into public waters is prohibited. Insecticides, such as those containing the bacteria Bacillus thurgiensis var. israelensis (Bti), are available at many nurseries and garden supply centers and can be used to treat mosquito breeding sites on your property.

In general, natural ponds and lakes are not sources of mosquito breeding, because permanent bodies of water usually contain fish and other predators that would consume mosquito larvae. 

There are also ways homeowners can minimize the annoyance caused by adult mosquitoes. Mosquitoes prefer to rest in shady, calm areas and will avoid more open sunny, breezy areas.

Mowing tall grass will reduce places where mosquitoes can rest. Mosquitoes are most active around dawn and dusk although some, such as the common saltmarsh mosquito, may be active throughout the day or may be more active during cloudy, humid weather.

Tips on reducing the chances of getting bitten by Mosquitos

Another excerpt from the announcement:

Simply avoiding outdoor activity during these peak mosquito times can minimize contact with mosquitoes.

To reduce the chance of being bitten when outside, wear protective clothing such as long sleeves, long pants and head cover.

Light-colored, loose-fitting clothing is preferable because dark clothing radiates more heat and attracts more mosquitoes.

Insect repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus can be used by most people and are often effective for varying lengths of time.

Permethrin, a synthetic pyrethroid that is widely available for repelling and killing ticks, also repels and kills mosquitoes.

It is applied to clothing and provides longer-lasting protection. Do not apply permethrin products directly to skin.

Although not marketed as repellents, there are several cosmetic liquids and creams that claim some level of mosquito repellency. These products may effectively repel when mosquito pressure is light, but need to be reapplied frequently.

The U.S. Environmental Protection Agency (EPA) provides further information on the use and effective use of repellants.

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