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Eliminating mosquito breeding sites can help reduce risk of Zika, West Nile virus in Indiana

May 26, 2016

Taking steps to knock out potential mosquito breeding sites can greatly reduce the risk of Zika and West Nile virus in Indiana as the local mosquito season ramps up, says Purdue University medical entomologist Catherine Hill.

According to recently revised maps from the U.S. Centers for Disease Control and Protection, the possible geographical range of the Aedes aegypti mosquito, the primary vector of the Zika virus, could include southeast Indiana. The estimated range of the Aedes albopictus mosquito, which is also capable of transmitting Zika, could cover most of the state.

Indiana is already home to species of Culex mosquitoes, the vectors of West Nile virus.

Because Culex and Aedes mosquitoes typically breed in containers, eliminating these sites can go a long way toward both reducing the transmission of West Nile virus and preventing Zika from becoming established in Indiana, said Hill, Showalter Faculty Scholar.

"This is a two-for-one deal," she said. "While the chance of Zika infecting local mosquito populations is probably low, we can further reduce this risk by controlling Aedesmosquitoes. These steps have the added bonus of helping us control the mosquitoes that vector West Nile virus, a perennial problem in the state." 

Aedes aegypti mosquitoes have been detected occasionally in Indiana - probably brought in via imported goods such as used tires, Hill said - but local populations are not likely to become established because they cannot survive the winter. Still, the mosquitoes could produce several generations in the summer, heightening the need for the public to exercise smart mosquito control efforts and take steps to prevent mosquito bites.

"Getting rid of sites that collect water around houses, workplaces and recreational areas can go a long way to controlling mosquito populations and reducing the chance of disease transmission of both Zika and West Nile virus," she said.

Steps to reduce potential mosquito breeding sites include:

Personal protection measures against mosquito bites include using a U.S. Environmental Protection Agency-approved mosquito repellant, wearing clothing with long sleeves and pants and staying indoors during the day, the typical feeding time for Aedes, and at dusk through dawn, when Culex mosquitoes typically bite.

The public should also take precautions to prevent local transmission of Zika in Indiana, she said.

Local transmission of the virus could occur when a person infected with Zika is bitten by an Aedes aegypti or A. albopictus mosquito in Indiana and passes the virus to the mosquito, which then infects another person when it takes its next blood meal. This could lead to the virus becoming established locally, presenting the possibility of a seasonal cycle of Zika when mosquitoes are active.

"We don't want Zika to become established in Indiana, but because we could potentially have the two species of mosquitoes that can transmit the virus, there's a chance that could happen," Hill said.

More than 540 cases of Zika virus have been reported in the continental U.S. since the beginning of the year, all of which were acquired by traveling to countries with active Zika transmission. No locally-transmitted cases of Zika infection in the continental U.S. have been reported, but the virus is being actively transmitted in Puerto Rico, the U.S. Virgin Islands and American Samoa.

People who return to or visit the U.S. from Zika-infected areas should take precautions to avoid spreading the virus to local mosquitoes by staying indoors and using insect repellents, Hill said. People who show symptoms of or test positive for Zika should follow these precautions for three weeks.

About 80 percent of people infected with Zika will likely not even realize they have it, Hill said. The remaining 20 percent may experience mild symptoms such as rash, fever, red eyes and joint pain.

In pregnant women, however, Zika can cause a serious birth defect known as microcephaly, as well as other severe fetal brain defects.

There is also a suspected link between Zika and Guillain-Barré syndrome, a condition in which the immune system attacks the nervous system, potentially resulting in paralysis.

Zika is primarily transmitted by bite from an infected mosquito but can also be passed by a pregnant woman to her fetus during pregnancy and by a man to his sexual partners. Using condoms can help prevent sexual transmission of Zika, but not having sex is the only way to be sure that someone does not get sexually transmitted Zika virus, according to the CDC.

A free infographic on how travelers can protect themselves from mosquitoes in areas with active Zika transmission is available through the Purdue Education Store at https://edustore.purdue.edu/item.asp?Item_Number=E-269-W.

Guidelines and recommendations will evolve as researchers and health officials learn more about Zika, and the public should stay abreast of these changes, Hill said. The CDC offers multiple resources on Zika, which can be accessed at http://www.cdc.gov/zika/. Information about Zika from the Indiana State Department of Health is available at http://in.gov/isdh/26910.htm.

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