Rutgers-Newark scientist: Mosquitoes may carry lethal parasite

08/11/04

Think before you swat, advises researcher

(NEWARK) – Brush, then squash. Remember those three words and that technique the next time you catch a mosquito dining on your arm or leg, and you'll go a long way to protecting yourself from a potentially lethal parasitic micro-organism that may be in the mosquito, and is especially dangerous to those with weakened immune systems.

A study by Rutgers-Newark biology professor Ann Cali and others published in the New England Journal of Medicine in July indicates that microsporidia, a group of opportunistic single-celled micro-organisms that can invade and devour virtually any kind of human cell, may have entered and broken down the muscle tissue of a Pennsylvania woman when she crushed a mosquito over the site where it had been drawing blood. The woman later died as a type of microsporidia called B. algerae, known to reside in the tissues of mosquitoes, systematically consumed muscle fibers in her body, leaving the muscles unable to contract and respond to mental commands.

Cali, who serves as a consultant for the Centers for Disease Control (CDC) and the Armed Forces Institute of Pathology at Walter Reed Army Hospital, theorizes that the B. algerae in the mosquito may have been ground into the wound left by the insect's hypodermic-like feeding tube. Mosquitoes secrete an anti-coagulant to keep blood from clotting as they drink, temporarily leaving a clear passage directly into the bloodstream.

New research by Cali and one of her graduate students will be aimed at identifying how prevalent B. algerae is in mosquitoes in New Jersey through the collection and examination of specimens across the state.

"Microsporidia kill people because they stay below the radar," Cali observed.

Studies spearheaded by Cali have identified many of the dozen kinds of microsporidia now known to infect humans. About 1,500 species of microsporidia have been found infecting a wide variety of life forms. Their spores – a dormant stage in the creatures' life cycle – inhabit virtually every surface water source, becoming active microsporidia once they have been ingested by an animal susceptible to infection by that particular species.

Until recent research by Cali and her co-authors proved otherwise, the conventional scientific wisdom was that B. algerae, a microsporidium found in some mosquitoes, could only invade cells on the surface of the human body because they couldn't survive in the higher temperatures of deep tissue. Several types of microsporidia can be lethal in human beings, although a healthy immune system is usually an adequate defense.

Cali notes that AIDS patients, organ-transplant recipients and cancer patients undergoing chemotherapy – who have a low white blood-cell count – need to take extra care to avoid ingesting microsporidial parasites. She recommends that they always boil tap water before consuming it or stick to bottled water – as long as the source of the bottled water is deep springs or wells where microsporidia are unlikely to be present due to the absence of food sources.

"Prevention is so much better than cure," Cali said, adding that although treatment for some types of microsporidia shows promise, "Whenever we start dealing with parasites in our cells, it's very difficult to kill them without upsetting our body's other processes."

With mosquito season underway in earnest, Cali recommends some simple, common-sense approaches to avoid mosquito bites and resultant infections in addition to her brush-then-squash technique, which moves any B. algerae in a mosquito's body away from the vulnerable wound site.

If people are concerned about spraying insect repellents containing DEET on their skin, they can wear lightweight, long-sleeved shirts and long pants, and spray the DEET on the fabric instead. Taking garlic capsules, which cause the release of an odorless vapor through the pores that insects find unappetizing, also can be effective.

Another approach involves coating exposed skin areas with a bath oil product called Skin So Soft, which has proven so effective that U.S. armed forces operating in swampy, mosquito-rich areas now routinely carry it with their other gear. Avoiding being outside at dawn and dusk, when mosquitoes are most active and prevalent, is another effective tactic, she adds.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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