Mosquito season could be worse

CMU researcher: Michiganders’ risk of diseases from bites is comparatively low

Experts on Point is a University Communications series focusing on CMU faculty who have special insights into interesting, important and timely topics.

It's August, and we're all tired of mosquitoes. Too bad they're not tired of us.

With at least a month of summer weather still to come, the buzzing, biting nuisances are still out in force, ready to leave an itchy welt in trade for a little of your blood.

Michael Conway

Can't we stop them? Don't they carry diseases?

Michael Conway has answers. He is an associate professor of microbiology in Central Michigan University's College of Medicine and an expert on mosquitoes and the viruses they carry.

Q: What current mosquito research are you doing?

A: Our tests with people hypersensitive to mosquito bites suggest that the reactions that occur on your skin are somehow beneficial to the survival of the mosquito by enhancing its blood-feeding efficiency. We are trying to figure out if the itch promotes the blood-feeding process.

Q: How are you conducting this research?

A: We have an Institutional Review Board-approved human subjects study where participants allow up to three Aedes aegypti mosquitoes, confirmed to be pathogen-free, to feed on their forearm. We determine how many times the mosquitoes probe the skin and how much blood they consume, and then we correlate these feeding parameters with the hypersensitivity status of the participants.

Q: What kind of diseases do mosquitoes carry?

A: Michiganders should feel fortunate compared with other regions in the world in that we only have a few arboviruses of concern, and even those are rare. They are West Nile virus and Eastern equine encephalitis. Michigan reported its first case of West Nile in June in a captive hawk in Lapeer County. There has not been a case of EEE reported in Michigan yet this year.

There are occasional sightings of dangerous invasive species, like the Asian tiger mosquito, which can carry Zika and dengue virus. They aren't necessarily permanent residents that have learned how to survive our colder weather.

Q: How can people reduce their risk of being bitten and contracting these diseases?

A: These potentially fatal diseases can be prevented by taking common precautions such as avoiding the outdoors when mosquitoes are most active, wearing long and loose-fitting clothing, using mosquito repellant and staying away from standing water.

Q: How are mosquitoes best controlled in wide areas?

A: It is up to each community. Some do targeted spraying to control the numbers. On an individual scale, you should remove standing water on your property and encourage neighbors to do the same. If you live near a swampy area, you can buy baited traps to capture and kill large numbers of mosquitoes. If you feel you need to apply chemicals, you must contact a professional.

Q: What makes mosquito bites itch, and why are some people more sensitive?

A: Mosquito bites itch because some people develop a reaction to mosquito saliva proteins. These proteins are inoculated into your skin when the mosquito probes for blood. If you are hypersensitive, these proteins stick to antibodies on the surface of mast cells, causing the release of a chemical called histamine. Histamine increases the amount of fluid at the bite site and sends a signal through your peripheral nerves that your brain interprets as itchiness.

Q: Why do mosquitoes bite?

A: Not all mosquitoes bite, just the females. They bite to draw blood to feed and lay their eggs. We typically aren't at the top of the menu. Some prefer deer and rabbits, while others prefer to feed on birds. Male mosquitoes are mainly sugar feeders, dining on the nectar of plants.

Q: Are there more mosquitoes this year?

A: It started out that way with the rainy early summer. As temperatures rose and rain ceased, their numbers collapsed, but they have normalized to a large extent.

Q: How long do adult mosquitoes live, and how long do their eggs survive?

A: Typically, a couple of weeks in good conditions. That gives them enough time to have blood meals and lay eggs. Some survive multiple rounds of blood-feeding and egg-laying before they die, but many die after one round. Most are eaten by bats and birds. Fish prey on mosquito larvae. Eggs can be laid in fall and last through the winter and hatch in spring.

About the expert

Michael Conway has developed a multidisciplinary approach to study the molecular biology, virology, medical entomology and evolution of pathogens such as dengue and Zika viruses. Current research projects include the identification of mosquito saliva proteins that modify virus dissemination in the host, identifying host blood factors that modify virus acquisition in the mosquito, and developing technologies to diagnose and interfere with virus transmission.

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