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Beware: The “Ankle-biter” Mosquitoes

Beware: The “Ankle-biter” Mosquitoes

It's the end of summer and the mosquitoes are biting. Two invasive (non-native) mosquito species have been identified in California and other parts of the United States. These mosquitoes bite around the ankles all day long—not just at dawn and dusk—and they bite multiple times in one sitting. So, what are these so-called “ankle biters”? These are the Aedes albopictus mosquito, also known as the Asian tiger mosquito, and the Aedes aegypti, or the yellow fever mosquito. These winged creatures apparently arrived in Southern California on a container ship from Asia several years ago.

I have seen patients throughout the summer with mosquito bites—as many as 20 bites on one extremity. For some patients the bites are intensely pruritic immediately, but for others the itch sets in after a day or so and the bites become inflamed at that time. The bites cluster around the ankles and other exposed body areas, typically the extremities. These mosquitoes can cause more than an itch; they can carry diseases including West Nile, Zika, dengue fever, yellow fever, and chikungunya. Of these, West Nile virus is the most common mosquito-borne illness in the continental United States.

These mosquitoes can survive year-round in tropical and subtropical climates. They are most attracted to humans but will also bite animals, such as dogs, cats, and birds. They approach humans from behind and aim for the ankles and elbows—areas that are frequently exposed in warm weather. About 3 to 5 days after feeding on blood, the female lays eggs in standing water—in places such as a decaying tree hole, plant reservoir, or an artificial receptacle with water. Consider these suitable habitats for these mosquitoes: flower pots, discarded tires, bottle caps, plates under potted plants, cemetery vases, buckets, tin cans, clogged rain gutters, ornamental fountains, drums, water bowls for pets, birdbaths, etc. These are especially ideal if they are located close to where humans live, providing easy access for blood meals.

Eggs are laid over a period of several days, are resistant to desiccation, and can survive for 6 months or more in warm climates. The larvae hatch when water or rain floods the vessel containing the larvae. The life cycle from egg to adult can take place in 7 to 8 days. The lifespan for adult mosquitoes is 3 weeks. The female Aedes albopictus and Aedes aegypti need blood to produce eggs and are active in the daytime. The female Aedes albopictus is a very aggressive daytime biter; it has a rapid bite and peak feeding times are early morning and late afternoon.

Using an extra measure of caution with preventive measures for mosquitoes is a good idea. In your environment, eliminate any standing water containers or reservoirs, both natural and artificial. For personal protection, avoid outdoor exposure in early mornings and later afternoon, and wear protective clothing. Use of repellants—such as DEET, picaridin, oil of lemon eucalyptus, or IR3535 on exposed skin and/or clothing (not under clothing)—is also recommended.

References
  • California Department of Public Health. Aesdes aegypti and aedes albopictus mosquitoes. www.cdph.ca.gov/Programs/CID/DCDC/Pages/Aedes-aegypti-and-Aedes-albopictus-mosquitoes.aspx. Accessed September 23, 2019.
  • Centers for Disease Control and Prevention. Dengue and the aedes albopictus mosquito. www.cdc.gov/dengue/resources/30jan2012/albopictusfactsheet.pdf. Accessed September 23, 2019.
  • Centers for Disease Control and Prevention. Dengue and the aedes aegypti mosquito. www.cdc.gov/dengue/resources/30Jan2012/aegyptifactsheet.pdf. Accessed September 23, 2019.

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Filed under: Infectious Diseases, Public Health

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