Zika mosquito ‘goes where the people are,’ says researcher

By Linda Weiford, WSU News

Zika-mosquito---wikipedia-webPULLMAN, Wash. – How can a slow-flying insect tinier than a paper clip and as light as a Kleenex tissue be to blame for the global health emergency declared this week?

The mosquito, Aedes aegypti, “isn’t some tropical forest-dweller that’s mostly isolated from people. It’s urban – it goes where the people are,” said entomologist Richard Zack of Washington State University. His research has taken him to Latin American countries where the mosquito is known to be spreading the Zika virus.

Richard Zack

“Aedes mosquitoes thrive in tropical and subtropical urban centers and require only a small amount of standing water to breed,” he said. “A tin can or a vase with just an inch of water is all a female needs to lay her eggs,” which number about 100 at a time.

The World Health Organization has sounded the alarm that Zika virus – carried by A. aegypti and believed to be linked to neurological problems in newborns and, to a lesser degree, adults – is a “public health emergency of international concern.”

Fueling the virus’ spread is the fact that the mosquito is urban, feeds almost exclusively on humans and bites during the day, said Zack: “Unlike many other mosquito species, this one doesn’t do its feeding at night when people tend to be indoors. Instead, it’s active when people are outside and much more accessible.”

Efficient transmitting machine

A. aegypti has evolved to live close to humans, making it better at transmitting diseases than most types of mosquitoes. Behind the Zika headlines, the mosquito transmits other infections as well, including yellow fever, chikungunya and dengue.

“Females need blood in order to produce,” Zack said. “After they pick up Zika, yellow fever or another pathogen from the blood of an infected person, there’s a strong possibility that they’ll pass the virus on through their saliva to the next person they bite.”

While Zika infections don’t appear to be dangerous to most people, there is increasing concern over its suspected link to a surge in babies born with brain defects and abnormally small heads, particularly in Brazil and Colombia. Health officials are also monitoring an uptick in the number of adults diagnosed with Guillain- Barre syndrome, a potentially paralyzing nerve disorder.

Named after the Zika forest in Uganda where it was discovered in 1947, the virus is believed to have leapfrogged to Southeast Asia and, more recently, the South Pacific and then Latin America.

Considering that these A. aegypti fly only a few blocks during their entire lives, how are they traveling so far?

They’re not flying – at least, not with their own wings, said Zack. Rather, “they’re being transported long distances by way of global travel and commerce.”

Worse than lions, bears

People traveling to Latin American countries should take precautions by going online to see if Zika advisories have been posted for their destinations (see CDC Zika Travel Information: http://wwwnc.cdc.gov/travel/page/zika-travel-information). If so, travelers should bring plenty of insect repellent and wear clothes that cover arms and legs, said Zack.

Mosquitoes in general cause more human suffering than any other creature on the planet, and Zika is but one disease they spread, he said: “On a worldwide scale, people should be far more worried about being bitten by a mosquito than by a lion or a grizzly bear.”


Richard Zack, WSU entomologist, 509-335-3394, zack@wsu.edu
Linda Weiford, WSU News, 509-335-7209, linda.weiford@wsu.edu