Many people are in a frenzy and expressing concern about spending time outdoors because of the recent announcement of locally-transmitted cases of Zika virus in south Florida. Questions are being asked about controlling mosquitoes locally. Dr. Michael Waldvogel, NCSU Extension Specialist and Professor, provided the following information on controlling mosquitoes in NC.
The CDC had reported 1658 cases of Zika virus across the U.S as of July 27. New York and Florida led the nation with 449 and 307 cases, respectively (over 45 percent of all U.S. cases). North Carolina was tied with Minnesota at number 15 with 21 confirmed cases. Pennsylvania has the only recorded accidental laboratory exposure. With the exception of Florida’s four local cases and one accidental exposure in a lab in Pennsylvania, the remaining cases (in NC and nationally) were travel related. The people who became infected were outside the U.S. or had sexual contact with someone who had become infected while outside the U.S. Compare these statistics with the Commonwealth of Puerto Rico which has over 4600 locally transmitted cases of Zika virus.
This is not meant to downplay the significance of the disease. It is important for North Carolinians to understand that this is not south Florida. Seeing mosquitoes in yards now, as you likely do every summer, does not mean that you are at greater risk of getting Zika virus. There is no need to collect mosquitoes and try to have them tested for Zika. A mosquito has to bite an infected person within a few days after that person becomes ill in order for it to pick up the virus and then transfer it later when it bites someone else. The cases of Zika virus in North Carolina have so far been people who became infected while outside the U.S. The likelihood of them being bitten by a mosquito within the early days of the infection (when the virus is replicating) is extremely low. A mosquito frequently cannot pick up enough virus from biting a sick person and transfer it to another person.
There are about 65 species of mosquitoes in North Carolina. The primary “vector” or transmitter of Zika virus is the “yellow fever mosquito”, Aedes aegypti, which has not been found in recent surveys in North Carolina. It could possibly show up at some point but the primary “mosquito of interest” is the Asian tiger mosquito (ATM), Aedes albopictus which spreads our “resident” diseases. West Nile virus (WNV), eastern equine encephalitis (EEE) and LaCrosse encephalitis (LAC) show up in relatively low numbers in our state nearly every year. It is important to understand the difference between these diseases and Zika virus. The reason that WNV, EEE, and LACV are more likely to occur here is that those viruses are found in local reservoirs including wild bird populations (such as robins and crows) and some rodents. The only way for a person (or horse) to get one of these diseases is by being bitten by a mosquito that had first found and fed on an infected bird.
It is important to understand how to reduce mosquito populations to help reduce both the nuisance biting aspect as well as the risk of exposure to other mosquito-borne diseases. Long-term impact on mosquito populations starts with some simple and common sense tactics. Asian tiger mosquitoes like to feed during the daytime, but it will feed “dawn to dusk”. If we really want to put a dent in the mosquito populations around our homes and communities, then we need to focus on source reduction. We need to get out in our yards and community and find ways to disrupt or eliminate the many mosquito breeding sites that can be around our homes.
If you want to be proactive about controlling mosquitoes in your yard and neighborhood, then make the effort to reduce the number of sites that become mosquito breeding grounds. Asian tiger mosquitoes do not breed in lakes or ponds but prefer to lay eggs in temporary resources like objects or areas that fill with debris and water. The debris is a food source for the hatching larvae (immature mosquitoes). As the water slowly stagnates, it attracts more female mosquitoes. The eggs are very durable and can survive periods of drought. It may actually take several periods of flooding and drying in these areas before all of the mosquito eggs hatch. When the eggs hatch, a new generation of mosquitoes can be produced in two weeks. To reduce mosquito populations and reduce the likelihood of mosquito-borne diseases, then we need to focus our attention on a community-wide effort to “tip and toss” the mosquito breeding sites.
Keep mosquitoes out of your home and business by keeping window and door screens in good condition and fitting properly. Take precautions when you are outdoors for work or recreation. Wear long-sleeved shirts and long pants and apply insect repellent to your clothing and/or exposed skin. DEET is a commonly used product but select a repellent that fits your needs and preferences. Read and follow the product label.
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