State Researcher: Mosquito Viruses Threaten Fairfield County

When it comes to the proliferation of mosquitoes in Connecticut and the viral diseases they transmit, the Interstate 95 corridor from Greenwich to New Haven is historically the "hot spot," according to Dr. Theodore G. Andreadis, chief entomologist at the state's Agricultural Experiment Station in New Haven.

During a phone interview Friday, Andreadis said mosquitoes in Connecticut can carry seven virus species, with West Nile Virus and Eastern Equine Encephalitis the most prevalent.

While Lyme disease and other tick-borne illnesses are the number one health concern in the state, Andreadis said, "the unfortunate reality is Lyme won't kill you, but West Nile virus (and) Eastern Equine Encephalitis can."

Also, early stage illness from Lyme disease can be treated with antibiotics, he says, while there are no cures for West Nile virus or Eastern Equine encephalitis.

West Nile is a type of virus that causes encephalitis, or inflammation of the brain. The virus has been found in Africa, western Asia, the Middle East, the Mediterranean region of Europe, and the United States. Mosquitoes become infected with the virus after feeding on infected wild birds and then transmit the virus through bites to people, animals and other birds.

Right now, Andreadis warns, we have very high levels of West Nile virus-carrying mosquitoes circulating along the I-95 corridor.

The state has seen two human cases (in New Haven and Trumbull), he said, and officials know the weather conditions that Connecticut residents will experience in the coming week -- temperatures in the high 80s to low 90s, high humidity and warm temperatures at night -- "are very conducive for mosquito-biting behavior."

First identified in the United States, including Greenwich, Conn., in 1999, Andreadis says West Nile is an "exotic virus" that came from the Middle East and swept across the country.

Since then, the nation has seen more than 30,000 human cases, with more than 1,000 deaths, including 71 human cases and three fatalities in Connecticut.

Andreadis said it's unknown why Connecticut is the only northeast state not to have identified a human case of the encephalitis, even though mosquitoes carrying the virus have been located in the eastern half of the state. Worse than the illness caused by WNV, Andreadis said, even if you survive an EEE infection, you almost always have permanent neurological damage, and can be left with muscle weakness, fatigue and confusion.

Andreadis said that EEE has been in Connecticut "probably forever," and has a completely different ecology than West Nile virus, since it's transmitted by a woodland mosquito that doesn't like to feed on humans.

The Agricultural Experiment Station, which is a standalone state agency, is operating this year on a state budget of $200,000, Andreadis said, plus a $100,000 grant from the federal Centers for Disease Control and Prevention.

According to the station's website, 25 scientists and support staff conduct an annual statewide surveillance program for mosquitoes from June to October, with a network of 91 mosquito-trapping stations in 72 municipalities throughout the state.

Officials will trap and test over 200,000 mosquitoes annually, Andreadis said, and once a virus-carrying mosquito is trapped at a location, trapping increases to two or three times a week.

Andreadis described the complex, five- to seven-day process by which mosquitoes are determined to be carrying a virus as follows:

• Live trapped mosquitoes are brought to the Experiment Station where they are kept in a freezer to subdue them, and then kept in containers with dry ice (frozen carbon dioxide)
• Six people separate the mosquitoes by species and then grind up as many as 50 of the same species
• The ground material is spun in a centrifuge and any live viruses float to the top
• The virus material is put in a cell culture of African Green Monkey cells so more of the virus will grow. Cell cultures are then put in an incubator warmed to body temperature and checked daily
• DNA is extracted from the virus growth and subjected to polymerase chain reaction amplification, which identifies of the type of virus the mosquitoes were carrying

In terms of public health action, Andreadis said that when a virus is detected the local community is notified and a news release is posted on the station's website.

"What they do beyond that is entirely up to them," he said, including using repellents or avoiding certain areas at certain times of the day. "We don't advocate."

Connecticut has been very conservative in using pesticides, Andreadis says, employing them only when we feel there is a "pending epidemic that's immediately apparent."

According to Richard Wolf, Mosquito Management Coordinator at the state Department of Environmental Protection, "It's a last option with any (Connecticut) mosquito control program.

It almost requires a "notice of a public health emergency," Wolf said.

However, some towns, Wolf said, hire companies to spray insecticides throughout the summer to control mosquitoes.

During a phone interview Friday, Wolf said state authorized spraying of insecticides for mosquitoes requires a cooperative agreement between the commissioners of the DPH and the DEP, and would be based on the extent of illness and the number and species of mosquitoes testing positive.

Wolf said his department's budget to control mosquities this year is under $270,000.

In an Aug. 24 news release, the state Mosquito Management Program reported mosquitoes trapped in Darien, Greenwich, New Britain, Newtown, Stratford and Trumbull from August 12-18 tested positive for West Nile virus.

These are the first virus-positive mosquitoes identified in these five towns, the release said, and quoted Andreadis saying West Nile Virus is spreading to additional areas in the state and mosquitoes continue to be identified carrying the virus in previously identified areas, "indicating an increasing proportion of mosquitoes infected."

The state DPH says that so far this season, mosquitoes testing positive for West Nile Virus have been identified in 18 towns: Bethel, Bridgeport, Darien, Fairfield, Greenwich, Manchester, Meriden, Milford, Newtown, Norwalk, New Britain, Orange, Stamford, Stratford, Trumbull, West Haven, Westport and Wethersfield.

Also, it says two people living in New Haven and Trumbull have been reported infected with WNV this year.