How Canadian Scientists Plan to Fight Zika With Old Tires and Milk

Mosquitoes aren't just an itchy menace: they carry all sorts of diseases, including the Zika virus, which is plaguing large parts of the Americas and other countries around the world. Now, a team from Canada and Mexico has designed an environmentally friendly, low-cost way of fighting them: an egg trap made of old car tires and milk.

They've tested their design in Guatemala, and are setting their sights on expanding.

The trap is designed to attract the Aedes mosquito, the type of bug responsible for the spread of dengue fever, chikungunya, yellow fever, and the infamous Zika virus, which has prompted travel warnings to affected countries over concerns that infection may lead to birth defects and other complications.

The system uses a Canadian-designed trap built from two 50-cm sections of recycled car tire and fashioned into a mouth-like shape, with a fluid release valve at the bottom. Car tires are among the favourite breeding places of Aedes aegypti, the researchers explained—and they're inexpensive, which makes them even more attractive.

The system was modelled after a mosquito trap developed at Laurentian University in Sudbury, Ont. in response to the outbreak of the West Nile virus, and was originally used as a solution to attract Culex mosquitoes, which transmit West Nile.

In this version, which lures the Aedes bugs, there's a wooden or paper strip floating inside, like a raft, where the females lay their eggs. The strip is removed twice weekly for the eggs to be analyzed, then destroyed.

The liquid solution inside—which is milk-based and non-toxic—collects mosquito pheromone, a chemical released by female bugs to help others find safe breeding spots. This mosquito juice concentrates in the device over time and makes it even more attractive to other bugs who want to lay eggs.

It has a big advantage over pesticides, which are more expensive and can harm other species, like bats and dragonflies.

Over a 10-month period, researchers, who received funding from the Canadian government and Grand Challenges Canada, collected and destroyed over 18,100 Aedes eggs per month, using 84 traps throughout the Guatemalan town of Sayaxché. That's almost seven times the approximately 2,700 eggs collected monthly using the same number of standard traps—made from one-litre buckets filled with water—in the same area.

Throughout the study period, no new cases of dengue were reported in the area, which is remarkable given that these communities would normally experience two or three dozen cases a month. Researchers can't say for sure that it's because of their traps, but it's an encouraging sign.

Plans are underway to expand. The next step is to confirm the study's findings in different communities throughout the region, Gerardo Ulibarri, lead researcher and associate professor at Laurentian, told Motherboard via email from Mexico.

"I am opening the technology to the world," he said. "Whoever wants to use [these traps] to protect themselves or their family are welcome to adapt it to their region."

To that end, Ulibarri and his team have posted the design online, for anyone to use.

Given that this mosquito-busting trap is cheap and easy to make, their hope is that it will help communities protect themselves against disease-carrying mosquitoes. For those dealing with Zika, dengue, and similar outbreaks, that can't happen too soon.