This female Anopheles gambiae mosquito is feeding. You can see the blood swelling her abdomen.

Photo courtesy Centers for Disease Control & Prevention, photographer Jim Gathany

Mosquito Bites, Diseases and Protection

As mentioned before, only female mosquitoes bite. They are attracted by several things, including heat (infrared light), light, perspiration, body odor, lactic acid and carbon dioxide. The female lands on your skin and sticks her proboscis into you (the proboscis is very sharp and thin, so you may not feel it going in). Her saliva contains proteins (anticoagulants) that prevent your blood from clotting. She sucks your blood into her abdomen (about 5 microliters per serving for an Aedes aegypti mosquito).

If she is disturbed, she will fly away. Otherwise, she will remain until she has a full abdomen. If you were to cut the sensory nerve to her abdomen, she would keep sucking until she burst.

After she has bitten you, some saliva remains in the wound. The proteins from the saliva evoke an immune response from your body. The area swells (the bump around the bite area is called a wheal), and you itch, a response provoked by the saliva. Eventually, the swelling goes away, but the itch remains until your immune cells break down the saliva proteins.

To treat mosquito bites, you should wash them with mild soap and water. Try to avoid scratching the bite area, even though it itches. Some anti-itch medicines such as Calamine lotion or ­over-the-counter cortisone creams may relieve the itching. Typically, you do not need to seek medical attention (unless you feel dizzy or nauseated, which may indicate a severe allergic reaction to the bite).

Diseases

Mosquitoes can carry many types of diseases that are caused by bacteria, parasites or viruses. These diseases include:

  • Malaria - Malaria is caused by a parasite that is transmitted by an Anopheles mosquito. The parasite grows in your bloodstream and can produce symptoms that develop anywhere from six to eight days to several months after infection.The symptoms include fever, chills, headaches, muscle aches and general malaise (similar to flu symptoms). Malaria is a severe disease that can be fatal, but can be treated with antimalarial drugs. Malaria is prevalent in tropical or sub-tropical climates.
  • Yellow Fever - Yellow fever no longer occurs in the United States or Europe, but it is prevalent in Africa and parts of South America. It is transmitted by the Aedes aegypti mosquito. Yellow fever produces symptoms similar to malaria, but also includes nausea, vomiting and jaundice. Like malaria, yellow fever can be fatal. There is no treatment for the disease itself, only the symptoms. Yellow fever can be controlled by vaccination and mosquito control.
  • Encephalitis - Encephalitis is caused by viruses that are transmitted by mosquitoes ¬≠such as the Aedes mosquitoes or Culiseta mosquitoes. The symptoms of encephalitis include high fever, stiff neck, headache, confusion and laziness/sleepiness. There are several types of encephalitis that can be transmitted by mosquitoes, including St. Louis, Western equine, Eastern equine, La Crosse and West Nile. West Nile encephalitis is on the rise in the eastern United States, which has raised concerns about mosquito control .
  • Dengue Fever - Dengue fever is transmitted by the Asian tiger mosquito, which is native to East Asia and was found in the United States in 1985. It is also transmitted by Aedes aegypti in the tropics. Dengue fever is caused by a virus that produces a range of illnesses, from viral flu to hemorrhagic fever. It is especially dangerous for children (see Dengue Fever & Dengue Hemorrhagic Fever for more information).

We'll look at ways to reduce mosquito populations in the next section.