El Nino’s Summer Souvenir: Mosquito Boom?

Southern Californians headed out of town for vacation this year want to forget all about El Nino and its fallout of floods and mudslides. Unfortunately, El Nino is a global phenomenon, and one of its side effects is an explosion in populations of mosquitoes, which seek out standing water as a favorable breeding environment.

Depending on destination and weather conditions, travelers could be at greater risk this year of contracting a mosquito-borne disease.

The risk varies from location to location due to the nature of El Nino. Known technically as the “El Nino-Southern Oscillation,” the phenomenon describes a change in the ocean atmospheric system in the Pacific that contributes to weather changes worldwide, resulting in increased rainfall in some areas and drought in others. But even in low-risk locations with excellent mosquito abatement programs, travelers should not get a false sense of security.

Among the diseases that can be spread from mosquitoes to humans are malaria, dengue fever and various forms of encephalitis. Symptoms are similar to those of flu--fever, headache and joint pain.

So, are there destinations to avoid at all costs?

Even before El Nin~o, certain destinations were arousing concern among mosquito-control experts.

In recent years, dengue fever, a tropical disease, has emerged as a major public health problem along the Texas-Mexico border, according to researchers at the International Conference on Emerging Infectious Diseases in March in Atlanta.

Certain other states and regions historically have had high mosquito populations, according to Dr. Kevin Kain, director of the tropical disease unit at the University of Toronto, and Dan Ariaz, president of the American Mosquito Control Assn. Among historic hot spots, other than Texas, are Florida, Louisiana, Mississippi, Arizona, southern Nevada, Utah, Washington, Idaho, Oregon, Alaska, Georgia, South Carolina and North Carolina.

Travelers to the Pacific Northwest and Northern California, especially the Bay Area, should take precautions such as using repellent, Ariaz advised.

Overseas, the risk of mosquito-borne illness is greatest in Southeast Asia and in Central and South America, Kain said.

Closer to home, Southern Californians who venture to natural areas such as Angeles National Forest should be aware that these areas are not covered by mosquito abatement districts. “In normal years, it doesn’t present a problem,” said Gail Van Gordon, a public health entomologist with the Los Angeles County Department of Health Services. But this year, “it would be prudent to take precautions” such as wearing repellent and long sleeves.

Unfortunately, travelers will be hard-pressed to research the mosquito status of an area before going, said Mike Murray, a public health environmentalist with the Washoe County (Nev.) District Health Department. It’s not something the local Chamber of Commerce would be forthcoming about, he said.

But travelers to popular tourist destination sites such as amusement parks probably have less to worry about, he said. “In tourist areas, generally [mosquito abatement] is a high priority.”

Disney World Resort in Florida, for instance, operates its own mosquito abatement program, said Diane Ledder, a resort spokeswoman. “It includes spraying and applying larvacide to reduce mosquitoes in several different ways,” she said. “Most mosquito control is done at a time when guests are not present, and we try to keep chemical control to a minimum,” she added.

But even in lower-risk areas, take precautions against being bitten. “Simple precautions work best,” said Kain, and repellents are at the top of the list. “Ones with DEET (N, N diethyl-m-toluamide) are the only ones that work well.” He added that Citronella-based repellents, often promoted as natural, “do not work as well.”

The CDC recommends the use of repellents with DEET concentrations of 30% to 35% but no higher. These are effective for about four hours, according to the CDC.

“You don’t have to sheep-dip your kids in 95% DEET,” said Kain, who uses repellents on his own 8-year-old twin boys.

Permethrin, an insecticide, can be sprayed on clothing and bed nets to repel mosquitoes as well.

While seeing a doctor for a simple mosquito bite, especially in the U.S., is generally considered overkill, it can’t hurt for travelers who have been bitten to be alert to the symptoms common to serious mosquito-borne diseases.

Healthy Traveler appears the second and fourth week of every month.