Client Education: Dealing with Mosquitoes and West Nile Virus

The following questions represent those most frequently asked about WNV, according to government sources (westnilevirus. nbii.gov/mosquitoes.html). By helping clients understand the breeding and eating habits of mosquitoes, you can help them protect their pets from acquiring WNV.
Why do mosquitoes bite?
Only female mosquitoes bite—they require a blood meal to acquire the protein needed to produce eggs. Females lay multiple batches of eggs during their life span, and a new blood meal is needed to produce each batch. Different mosquito species prefer different host species—some mosquitoes seek blood meals from birds, others from mammals, and some are generalists. The female inserts her needle-like proboscis, a slender, tubular, feeding and sucking organ, under the victim's skin, drawing blood into her abdomen. She feeds until her abdomen is full or she is discovered and brushed away.
Why do mosquitoes seem to bite some victims but not others?
This phenomenon is not completely understood. Mosquitoes are attracted by the carbon dioxide that humans and animals exhale. They may also be attracted by various odors (such as perfume, perspiration, lactic acid, or detergent) that combine in unique ways to make one victim more attractive as a meal than another. Because dark colors absorb heat and lighter colors tend to reflect heat, mosquitoes attracted to humans tend to select victims dressed in darker clothing.
Why do mosquito bites itch and swell?
The itching, swelling, and burning from a mosquito bite are actually caused by the body's autoimmune response to the saliva injected by the mosquito when she feeds. This saliva contains anticoagulating agents that prevent the victim's blood from clotting as it is being sucked into the mosquito's abdomen. A bite may take several days to heal and stop itching, even with treatment using anti-itch products.
Where do mosquitoes breed?
Mosquitoes breed in wet, swampy areas where they lay their eggs. The eggs hatch in the water, and the young mosquitoes spend the pupal stage there. Mosquitoes lay eggs in both fresh and polluted water and seek still water, such as small puddles, ditches, and ponds. Even a small amount of standing water, such as the bottom of a flowerpot, can pro-
vide a sufficient habitat for mosquito eggs. Eggs usually hatch about 5 days after they have been laid. Thus, a key factor in mosquito prevention is the elimination of standing water.
What is the average life span of a mosquito?
Like most insects, mosquitoes are a prime food source for birds, amphibians, and spiders. Between predators and extreme weather events, such as drought and harsh rains, most mosquitoes live for an average of about 2 weeks in their adult form. If they manage to escape predators, females from some mosquito species live to about 2 to 3 months of age. Females that enter adult form late in the season may hibernate as cooler weather approaches and can emerge the following spring to lay eggs. In many species, eggs laid before the onset of cold weather can also survive through winter, even without water, rehydrating in spring rains to go through larval, pupal, and adult stages.
Will winter bring an end to West Nile virus-carrying mosquitoes?
Yes and no. Like snakes and amphibians, insects are coldblooded and cannot regulate their body temperature. Because they depend on their environment to maintain a sufficient body temperature, mosquitoes "disappear" in regions subject to cold winters. Female mosquitoes that mate in the fall and survive into the onset of winter can hibernate and emerge in the spring ready to find the first available blood meal and lay their eggs. Some mosquito species can also lay eggs capable of surviving extreme weather conditions, such as cold, ice, and drought. Moisture produced by spring rains and melting snow and ice can cause these eggs to hatch, and the mosquitoes then progress through larval, pupal, and finally adult stages to begin the cycle anew. In the warm and humid climates of the Southeast and Gulf Coast, mosquitoes can thrive year-round.
How many types of mosquitoes are there?
According to the American Mosquito Control Association, there are more than 2,500 mosquito species worldwide. About 200 species are found in the United States. According to the National Pesticide Information Center, 36 species occurring in the United States have tested positive as carriers of WNV. The most common carrier is the Culex pipiens (northern house) mosquito. Other carriers include Culex restuans, Aedes albopictus, Culex quinquefasdatus (southern house mosquito), and Aedes vexans.