April 10, 2016

Researchers use Zika mosquitoes' own perfume to lure them to lay eggs in trap

A team of innovators from Canada and Mexico have successfully tested a low cost, environmentally-friendly way of destroying the eggs of the mosquito genus that spreads dengue, and likely spreading the Zika virus.

The system includes an innovative Canadian-designed trap called an "ovillanta," created from two 50 cm sections of an old car tire, fashioned into a mouth-like shape, with a fluid release valve at the bottom.

Inside the lower tire cavity, a milk-based, non-toxic solution developed at Sudbury's Laurentian University lures mosquitoes. Inserted to float in the artificial pond is a wooden or paper strip on which the female insect lays her eggs. The strip is removed twice weekly, analyzed for monitoring purposes, and the eggs destroyed using fire or ethanol.

The solution, which now includes mosquito pheromone (the female insect's chemical perfume that helps others identify a safe breeding site), is then drained, filtered, and recycled back into the tire. The pheromone concentrates over time, making the ovillanta even more attractive for mosquitoes.

During the 10-month study, the team collected and destroyed over 18,100 Aedes eggs per month using 84 ovillantas in seven neighbourhoods of the town of Sayaxche (population 15,000), almost seven times the roughly 2,700 eggs collected monthly using 84 standard traps in the same study areas.

A tantalizing but anecdotal observation was that there were no new cases of dengue reported as originating in the ovillanta study test area, a community that would normally anticipate two or three dozen cases in that timeframe.

Targeting mosquito eggs using the ovillanta, Dr. Ulibarri says, is one third as expensive as trying to destroy larvae in natural ponds and only 20% the cost of targeting adult insects with pesticides, which also harm bats, dragonflies and the mosquitoes' other natural predators.

An 'ovillanta' is created from two 50 cm sections of an old car tire, fashioned into a mouth-like shape, with a fluid release valve at the bottom. CREDIT Daniel Pinelo

F1000Research Zika and Arbovirus Outbreaks channel

Key to the overall system is an online training program to strengthen the mosquito control expertise of local health workers, coupled with a community engagement strategy that involves households in the regular maintenance of their ovillanta.

The community members collect the egg-laden strips of paper or wood from the ovillanta and pass them to the health workers, who conduct the monitoring and destruction using fire or ethanol.

The Aedes genus of mosquito - the principal genus that transmits Zika, dengue, chikungunya, and yellow fever viruses - has proven extremely difficult to control using other strategies, according to the World Health Organization.

A female, with a natural lifespan of up to three months, can start to reproduce in one week. Pesticide-resistance, dwindling resources, and an increase in mosquito-friendly environments have thwarted traditional methods of controlling the insect's rapid spread.

SOURCES - Eurekalert, F1000Research Zika and Arbovirus Outbreaks channel

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