Health

Published: Sunday June 8, 2014 MYT 12:00:00 AM
Updated: Tuesday June 10, 2014 MYT 4:38:48 PM

The mozzie Darth Vader

Aedes aegypti’s favourite breeding grounds revolve around manmade things, as this display shows. –Filepic

Aedes aegypti’s favourite breeding grounds revolve around manmade things, as this display shows. –Filepic

The mosquito that hosts yellow fever, dengue and chikungunya, does an excellent job at spreading those diseases to us humans.

It's not at all hard to imagine that Aedes aegypti is the Darth Vader of mosquitoes, an evil little creature bent on the destruction of mankind and a serial violator of Geneva Convention rules about biological warfare.

Almost every time there’s an outbreak of a tropical disease – yellow fever, dengue, and now, chikungunya (in the United States) – Aedes aegypti turns out to be behind it.

During the Spanish-American War, Aedes aegypti inflicted more casualties on US troops with yellow fever infections than the Spanish army did with bullets and bayonets.

“That’s kind of an extremely anthropocentric view of the subject,” cautions Roger Nasci of the federal Centers for Disease Control and Prevention (CDC), an expert on insect-borne illnesses.

Translation: That’s thinking too much like a human being.

Aedes aegypti is just doing what mosquitoes do, and doing it rather well.

Aedes aegypti is not the only mosquito that’s an important vector for disease,” Nasci explains.

“Other types of mosquitoes carry malaria and the West Nile virus.

“But it’s uniquely suited to spreading disease, because it likes living around people.”

Many of the 170 or so species of mosquitoes in the US prefer breeding environments that don’t necessarily bring them in close contact with humans.

They like to lay their eggs in swamps, or frequently flooded areas, or rainwater-filled crannies in rocks or trees.

Aedes aegypti, however, is happy to use stuff that humans bring to urban areas: buckets, tires, storage devices for potable water, essentially anything that holds a small pool of water,” says Nasci.

“And, unlike a lot of mosquitoes, they’ll feed indoors quite readily.”

Add to that a work ethic that would be admirable if you saw it among, say, roofers or Department of Motor Vehicles (DMV) clerks.

“Unlike mosquitoes who are used to taking their blood meal in one sitting, then going on their way to lay eggs, Aedes aegypti is patient with interruptions,” Nasci said.

“It bites your ankle, gets some blood, you shoo it away, and it goes on to the next person and the next, until it’s full.”

Feeding on multiple targets, of course, makes Aedes aegypti a prolific spreader of disease.

So does the fact that, for reasons scientists don’t fully understand, its body is a hothouse for viruses.

“Some mosquitoes, you can feed them boatloads of virus, and nothing happens,” Nasci says. “The virus just dies.

“But Aedes aegypti is extremely susceptible to viruses. The virus prospers, and then it gets passed along to people the mosquito bites.”

Aedes aegypti, like many of the diseases it carries, is originally from Africa.

But it arrived in North America hundreds of years ago, with the slave trade, and has spread throughout the southern US.

About the only things that ever seem to make a dent in its numbers are other mosquitoes, particularly the Asian tiger mosquito, Aedes albopictus, which first turned up at a Jacksonville, Florida, tire dump in 1986.

Aedes albopictus and Aedes aegypti both mate with the speed and discrimination of South Beach clubbers at closing time, which means they often have one another’s babies – but, being a mixture of two species, their offspring are sterile.

You might sneer that that’s what they get for a lack of sexual decorum, but that would be anthropocentric. – The Miami Herald/MCT Information Services

Tags / Keywords: Health, Aedes aegyti, mosquito, vector-borne diseases, dengue

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