AZ Pest:: Arizona Pest & Termite Control

Elizabeth Willott, a UA entomologist who is participating in the study, said an earlier warm season will result in a bigger peak in mosquito populations later in summer. Increased heat will be “a stress” for mosquitoes outside the urban area, she said, but in town they have plenty of places to seek refuge. “We provide little oases for them,” she said. “We mitigate the extremes.” Outbreaks will tax our ability to manage mosquitoes, said Paul Robbins, a UA professor of geography and regional development, who is exploring whether mosquito managers are doing a good enough job of thinking like the mosquitoes. “That nasty West Nile is sort of like a test model to see how we’ll deal with scarier stuff like Aedes aegypti and dengue fever,” he said. He’s not certain we’ll pass the test.

Dengue fever infects up to 50 million people a year, most in tropical or subtropical climates, and most with a mild illness, according to the World Health Organization. Symptoms range from a fever to severe headache, pain behind the eyes, nausea and vomiting. In its most extreme form of hemorrhagic fever, it attacks the vascular system, causing bleeding and sometimes death. Half-a-million people are hospitalized with the extreme form each year and about 12,500 die, the WHO reports on its Web site.

Should we be scared? 

“Don’t be too worried about it,” says Willott, whose years of research into the habits of our urban mosquitoes leads her to believe that our infrastructure and lifestyle will make it difficult for dengue fever to get established here. Unlike West Nile, in which ever-present bird populations carry the virus, dengue fever must be transmitted by the Aedes aegypti mosquito from an infected human to an uninfected one. We humans hide in summer. If the heat doesn’t drive us inside, those darned mosquitoes will. Aedes aegypti is active in daylight when most of us are inside. Infected people are even less likely to be out and about. “What do you do when you get sick?” asks Willott. “You go to bed.” Health specialists agree. “The big question is, ‘Why do we have such a robust population already and we’re not seeing any dengue transmission?’” said public health researcher Kacey Ernst. Ernst, an epidemiologist who studied malaria transmissions in Kenya, said she, too, suspects that protecting us are our infrastructure and possibly our heat. “Multiple things have to align before you have transmission of a disease,” she said. “You need mosquitoes that survive long enough for two bites of a human. You have to have access to a lot of people” “It might be the heat decreases the life span, and the mosquitoes are not living long enough,” she said. She has applied for research money to test that thesis. Dr. Michelle McDonald, the Pima County Health Department’s chief medical officer, told a conference last year that it is “not a question of ‘if’ but ‘when’ ” dengue will show up here. “Nobody would be at all surprised to find a case in Arizona,” she said last week. She noted documented transmission of dengue in Texas and outbreaks in northern Mexico. “My sense is we may not find ourselves with a sustained outbreak where it becomes endemic. I’m not super-worried, but I certainly think it’s possible we’ll see cases.”The U.S. Centers for Disease Control and Prevention urges monitoring and vigilance.”Prospects for reversing the recent trend of increased epidemic activity and geographic expansion of dengue are not promising,” reads its most current outlook.

The weapons we use to fight mosquitoes in Tucson often seem like they’re not enough.

McDonald says she got calls at the height of mosquito season in 2006, with the callers wondering why the county wasn’t “fogging” — spraying insecticide to tamp down the populations of adult mosquitoes. She got as many or more calls opposed to spraying, she said. That option is available, she said, in emergency plans, but it’s a decision to be made by individual jurisdictions — the cities and towns. Fogging is done in Maricopa County, she said, but not here. Willott opposes fogging for two reasons: It kills everything that flies, and it doesn’t target the populations that carry disease. “I happen to like butterflies,” she said. Willott is cutting back her university hours to become director of education and butterfly curator at Tucson Botanical Gardens. Fogging won’t do much to control our two species of disease “vectors,” Willott said. They’re hanging out by our eaves and windows and gutters, she said. Fogging is effective against the swarms of floodwater mosquitoes that pop up after intense summer storms, she said, but those ephemeral nuisances aren’t disease carriers.

We can best fight the disease vectors — the ankle-biters and the West Nile virus carriers — by making their habitat less ideal, said Willott. At the botanical gardens, where she was originally hired to reduce mosquito populations in the gardens and surrounding communities, the numbers are dropping, she said. They are also dropping in her own neighborhood, she said, because all her neighbors now know what to do. Robbins said he’s finding that Arizona has an “everyone for themselves” policy of handling the public health threat from disease-bearing mosquitoes. At the state Department of Health Services, which employs entomologists and epidemiologists, the policy is “to help communicate but not to mandate” to the state’s 15 county health departments, Robbins said. At the county level, there are no entomologists and little budget to do anything more than monitor the situation and lead education campaigns, he said. “Pima County does not have the resources. They’re really all about using education. They’re not going to manage mosquitoes. They are going to manage people,” he said.

Pima County’s McDonald says every governmental entity these days is working with restricted funding. If she had more money for vector control, she said, she’d do more monitoring for mosquitoes and diseases, but she also thinks education is the key to reducing mosquito populations. Willott agrees. “It’s amazing how much an educated citizenry can do,” she said.

Of course, they must first know the facts, which is why she’s spent years trying to get people to think about specific mosquitoes and suggesting ways to handle them. This is best done locally, she said. “If we had a centralized system, we might accomplish less,” she said. “The situations we deal with here are different from the irrigation canals, floodwaters and subdivisions around lakes in Maricopa County.” Robbins said there is a real need for all the governmental entities to begin planning for a potential explosion in mosquito populations and future outbreaks of disease. “Mostly, they’re so busy with the present, they can’t think about the future,” he said.

On StarNet: Search our database of Critters of Southern Arizona at azstarnet.com/special/critters