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Precautions Same Whether Zika Virus in Brazil or West Nile in Wyoming

July 13, 2016

That whine you may hear when out and about this summer in Wyoming isn’t a dinner bell for mosquitoes -- it’s more like Muzak in a fertility clinic while the females look for a blood meal to produce eggs.

And in areas where viruses like West Nile (WNV) in Wyoming reside, and Zika in Brazil and in other South American regions, it’s more like infected syringes flying through the air. But not all mosquitoes are medically relevant -- only specific species of mosquitoes can carry and transmit specific diseases, says Scott Schell, University of Wyoming Extension entomologist.

Schell, a member of Wyoming Mosquito Management Association, and other scientists use the phrase vector competency to describe a mosquito species’ ability to:

-- Take up a disease organism while sucking blood from a sick animal.

-- Have the disease replicate in them.

-- Eventually accumulate in the salivary secretions.

-- Retransmit the disease to the next blood meal victim.

The Aedes aegypti mosquito in Brazil does that with the Zika virus, just as Culex tarsalis does in Wyoming with WNV, Schell says.

C. tarsalis feeds from dusk to dawn in Wyoming. A. aegypti, whose common name is yellow fever mosquito, is a daytime feeder that often follows people indoors.

“They often go for the lower legs, are small bodied with a ‘light touch’ so most people don’t even know they are being bitten until they start to itch later,” Schell says.

Schell’s suggestions for those traveling to the Olympics are the same for anywhere there is a chance of contracting a mosquito-borne disease (including Wyoming).

“Wear long pants, use mosquito repellent, and try to minimize the opportunity for mosquitoes to bite you,” he advises. “I imagine most of the Olympic events are not going to occur where high transmission sites are, like the slums.”

Mosquito lifecycles play a part in the ability to transmit diseases. WNV is primarily a bird disease, and C. tarsalis feeds on nestling birds in the spring. When the birds fledge and leave the nest, C. tarsalis readily turns to mammals, such as humans and horses, for the next blood meal and transmits the disease.

Environment plays a role as higher temperatures increase the replication of the virus in the mosquitoes, Schell says, and temperature also controls the speed of the reproductive cycle of the mosquitoes. Some mosquito species’ immune systems successfully defeat viruses, preventing them from replicating.

The Zika virus is thought to be a primate (monkeys and great apes) disease from Africa. First detected in a monkey from the Zika Forest in Uganda in 1947, the disease was first isolated from a human in 1952 there, according to the World Health Organization (WHO). Maps of the disease’s progression show travel east from Africa to Asia in 1977-78, to Micronesia in 2007, to French Polynesia in 2013 and Brazil in 2014.

Authorities link the Brazilian outbreak to the flow of visitors into the country prompted by the 2014 FIFA World Cup, according to the WHO.

Symptoms include mild fever, skin rash, muscle and joint pain, and headaches. The disease can cause microcephaly in babies, an abnormally smaller head compared to other children of the same age and sex. The brain does not develop normally.

Scientists in Brazil only recently found the Zika virus in A. aegypti collected from the wild, Schell says. They had suspected A. aegypti carried and retransmitted the disease (it did so in captivity) but needed to find some infected in the wild to confirm it is the vector.

A. aegypti typically doesn’t move far from where hatched and keeps to human-created habitat. The Zika virus hot spots are in the tropical northern portion of Brazil, while most of the Olympic venues are in the south, around Rio de Janeiro.

“That reduces the risk of infection with Zika while attending the Olympics significantly,” Schell says.

An Olympics visitor to Brazil shouldn’t fear contracting the Zika virus any more than a Brazilian visitor to Yellowstone National Park contracting WNV, he says. The risk of infection is low, Schell says, despite some Wyoming counties having been in the top five nationally for WNV infections per capita.

“If they are going to visit the irrigated crop fields in Goshen County in the evening -- WNV hot spots -- on their way to Yellowstone, they should wear appropriate protective clothing, use mosquito repellent to reduce the risk, and enjoy their travels,” he says. “The same common sense approach applies if you are traveling to Brazil.”


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Chad Baldwin

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