Combating mosquitoes: Separating fact from fiction

BATON ROUGE — Summer is not far away, and with it will come swarms of mosquitoes, which bring the threat of West Nile virus, eastern equine encephalitis and the potential for other diseases like Zika virus. That’s why it’s important for people to distinguish fact from fiction when choosing a plan of defense to fight their bites.
“West Nile virus is something we’re going to have to deal with annually,” said LSU AgCenter medical entomologist Kristen Healy. “So whether or not Zika virus becomes an issue in Louisiana, it’s important to remember that you should always protect yourself from mosquitoes.”
Healy advises selecting repellents registered with the U.S. Environmental Protection Agency and applying them according to label directions.
According to the U.S. Centers for Disease Control and Prevention, insect repellents that contain DEET provide the best protection against mosquitoes. The EPA has determined DEET is not classifiable as a human carcinogen.
A DEET concentration of 4 to 100 percent merely indicates how long it will last, not that higher percentages will work better, according to the CDC. Ten percent would give nearly two hours protection, while 30 percent would last about five hours.
“Going above 50 percent doesn’t really give you any additional protection, so you’re better off going with the smaller percentage and reapplying, unless you’re going out in the deep woods for a long time,” Healy said. The CDC recommends avoiding products that combine DEET with sunscreen.
The American Academy of Pediatrics recommends that repellents for children contain no more than 30 percent DEET. Both the AAP and CDC warn that DEET repellent should not be used on children less than 2 months old.
“Reactions are rare, but when applying repellent, avoid eyes, the mouth and open wounds,” Healy said. “If you have small children, don’t have them apply it — you want to put it on your hands and apply it on them.”
Permethrin-based products should not be used directly on skin. They go on clothing, according to the CDC. “That’s why you should always make sure you follow the label instructions,” Healy said.
Some other popular repellents have active ingredients like picaridin, IR3535 or para-menthane-diol (PMD), also called oil of lemon eucalyptus because it’s chemically synthesized from that plant. The CDC warns against use of oil of lemon eucalyptus on children younger than 3.
Some people also mistakenly consider dawn, dusk and nighttime as the only times mosquitoes are out. But for the two species that are potential vectors for pathogen transmission, the Asian tiger mosquito (Aedes albopictus) and the yellow fever mosquito (Aedes aegypti), that’s not the case.
“They will bite at any time of day,” Healy said. “So limiting your exposure to specific times, like the middle of the day, isn’t going to really help.”
Wearing long sleeves and long pants is helpful, but mosquitoes can bite through thin clothing. Repellent may be sprayed on clothes but not applied to the skin underneath.
Wearing lighter clothes helps ward off mosquitoes as well. “But for the most part, they’re going to be attracted to our breaths. We exhale carbon dioxide, and that’s one of the things that draw them in,” Healy said.
Mosquitos also are attracted to the heat we generate as well as the odors the heat creates, she said.
Zika virus has been of particular concern to pregnant women because the disease can cause microcephaly and other severe fetal brain defects.
“Pregnant women should talk to their physicians, and they can recommend a product for personal protection,” Healy said.
Homeowners should keep standing water out of backyard containers, even small ones. Mosquitoes will “lay eggs in anything as small as a bottle cap — anything that can hold water for seven days,” Healy said. “If you have a bird bath or rain barrel, make sure you flush it out on a weekly basis.”
Healy also recommends supporting local mosquito control programs. One myth is that these departments spray indiscriminately.
“They actually sample populations continually throughout the season and base a lot of their control decisions on mosquito activity and virus activity,” she said. “People don’t know what goes into it, but it’s a pretty involved process, not just spraying.”
People with questions about which insect repellents are right for their needs, Healy recommends the EPA website www.epa.gov/insect-repellents/find-insect-repellent-right-you
“I would recommend any type of repellent over not using any repellent at all,” Healy added.