New way to trap, kill mosquito eggs may help fight Zika

Toronto: Scientists have successfully developed a low cost way to trap and destroy the eggs of the mosquito genus that spreads dengue, and is likely spreading the Zika virus.

The 10-month study, conducted in a remote, urban area of Guatemala, documented a cheap, easy system to reduce virus-carrying Aedes genus mosquitoes by capturing and destroying its eggs.

The system includes an innovative 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 Laurentian University in Canada 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, analysed 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.

The researchers, led by Gerardo Ulibarri of Laurentian University with collaborators Angel Betanzos and Mireya Betanzos of the National Institute of Public Health of Mexico, found the rubber ovillanta significantly more effective at attracting the Aedes mosquito than standard traps made from 1-litre buckets.

During the study, the researchers 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.

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, researchers said.

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

"We decided to use recycled tires - partly because tires already represent up to 29 per cent of the breeding sites chosen by the Aedes aegypti mosquitoes, partly because tires are a universally affordable instrument in low-resource settings, and partly because giving old tires a new use creates an opportunity to clean up the local environment," said Ulibarri.