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Approaches to vector control need revision, experts say
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Researchers must rethink current Zika virus control strategies and find even new ways to measure their success, according to speakers at a recent meeting on the subject.
Infectious Disease News Editorial Board member Lyle R. Petersen, MD, MPH, director of the CDC’s Division of Vector-Borne Infectious Diseases, also assessed nationwide vector surveillance, among other efforts, during the recent meeting hosted by his agency and the CDC Foundation.
The aim of the meeting was to discuss ways to monitor and control the virus that can cause microcephaly and other severe congenital problems, along with Aedes aegypti, the mosquito species largely responsible for spreading it.
“I think one of the themes of this meeting is that the extant control strategies are inadequate,” Petersen said as he summarized information shared by experts from around the globe.
“We still continue to have outbreaks. I think the Zika virus, its emergence, has caused to come to light all of the problems with the existing systems and control strategies that we have, and clearly, I think, some new paradigm is needed.”
Speakers presented data on strategies showing promise, including the use of insecticide sprays, genetically modified mosquitos, other organisms that prey on mosquitos, lethal traps and others. They touched on data concerning other viruses related to Zika, such as dengue.
But many approaches need to be tested further, Petersen said, and researchers have sometimes sought the wrong outcomes.
For example, he noted studies in which a method leads to significant reductions in insects causing diseases but no reduction in actual human infections.
“Existing tools that we have are inadequately tested in the field for efficacy in reducing human disease,” Petersen warned.
“There are quite a lot of entomological data. But there were several examples given where it looked like the intervention was going to work, but it really didn’t help reduce human disease,” he said. “And there were relatively few studies on actual disease reduction, even for things like dengue that have been around for quite a long time.”
Ben Beard, PhD, chief of the CDC’s Bacterial Diseases Branch, also stressed the need for well-designed studies and discussed the potential benefits of an array of strategies.
Noting that the Aedes spp. breeds in many hidden locations and even in tiny amounts of water, Beard said areas of concern can be hard to find. But health workers have built up what they call a “toolbox” of potential approaches to vector control.
Along with insecticides and other measures, they include other organisms like copepods — tiny aquatic crustaceans that can feed on mosquito larvae. Gambusia affinis, or the Western mosquitofish, serves the same purpose.
Other potential strategies use mosquitoes against their own kind. One such method involves genetic modifications to male mosquitos that kill their offspring when they are released into the wild and mate with females.
Beard said the advantages and drawbacks of these and other methods vary.
“All of the current available tools have distinct benefits and they have limitations,” he said, “and there are no silver bullets when it comes to controlling the Aedes aegypti mosquito … Successful control will rely on a comprehensive, integrated approach that includes multiple tools aimed at reducing both larval and adult mosquitoes.” – by Joe Green
Disclosures: Beard and Petersen report no relevant financial disclosures.