A new mosquito trap designed by a Canadian researcher is almost seven times more effective than conventional devices, according to a new study conducted in northern Guatemala, providing hope that the spread of mosquito-borne viruses such as Zika can be better controlled.
Laurentian University researcher Dr. Gerardo Ulibarri has been crafting and testing mosquito traps for years. His latest is called the "ovillanta." The low-cost trap, made from discarded tires and other recycled materials, has proven to be highly successful in Sayaxche, Guatemala, a region deemed at risk for viruses such as dengue, chikungunya and now Zika – all diseases carried by mosquitoes.
The target is Aedes aegypti, which is known commonly as the yellow fever mosquito and is suspected of transmitting Zika, a disease attributed to rising rates of microcephaly (children born with abnormally small heads) and other serious neurological disorders, such asGuillain-Barré syndrome, which can affect anyone.
The study, released Thursday, was conducted in seven neighbourhoods in Sayaxche during a 10-month period in 2015 and pitted 84 ovillantas against 84 ovitraps – one-litre bucket contraptions filled with water. During the study, ovillantas captured and destroyed 181,336 mosquito eggs, compared with 27,053 eggs eliminated by the more conventional traps, according to the study.
"We're destroying the second generation of mosquitoes," Dr. Ulibarri said. "By destroying the larvae and the eggs continuously, the second generation, or the third, or the fourth won't come out, so there's no experiential production of mosquitoes to bite and transmit diseases."
The study was funded by Grand Challenges Canada, an organization that supports global health initiatives.
"Dr. Ulibarri and his team are trying to build a better mouse trap, except it's a mosquito trap that's directed at the world's top public health emergencies," said Dr. Peter Singer, chief executive of Grand Challenges Canada.
Dr. Ulibarri said he and his team were initially targeting Aedes aegypti for afflicting the town with dengue. Little did he know the species would eventually become a vehicle for the Zika virus. Through sheer happenstance, traps were set on the advent of the outbreak during the spring of 2015.
Thirty-three countries have been impacted by Zika across the Americas, according to the World Health Organization, and the virus has infected millions.
"We were very timely," he said.
There were no recorded dengue cases in the town of 15,000 in 2015, he added. "I think we can extrapolate the reduction of dengue transmission to the new emergency, which is the Zika virus."
Dr. Ulibarri has had success closer to home with other traps. In 2008, he and a group of researchers reduced the number of mosquitoes that can carry West Nile virus by 90 per cent in northern Ontario. This genus of mosquito, called Celux, is suspected to be another Zika vector. It's also found in Central and South America.
"Those results are what prompted us to investigate whether we could extrapolate those results and the use of the trap against other species."
This idea led him tests in Mexico, then to Guatemala.
One reason why the trap is so effective is because the liquid solution inside the tire harbours a pheromone that attracts female mosquitoes. A paper or wood "landing strip" where female mosquitoes land and deposit eggs floats on top of the solution. Twice a week, especially during high heat, health workers count eggs and then destroy them by burning or poisoning them.
The solution becomes more concentrated every time it's recycled, making it even more attractive to the mosquitoes.
"The pheromone indicates to other females that that place is a good place for the babies to be born," Dr. Ulibarri said. "By recycling the solution and eliminating the larvae through a filter, we are using their own smells to attract more mosquitoes."
Finding a way to deliver a means to control viral diseases in economically strapped regions is a challenge, he said.
This is where the tire fits in. The town has a surplus of them, and using them is both cost-effective and reduces the need for spraying pesticides, Dr. Ulibarri said.
"They already had the tools. We just had to tell them how to transform them and how to use them to take care of their health."
A trap costs about $3.50, and three can be produced by a single tire.
Dr. Ulibarri said he is really impressed by the people in Sayaxche for their will to adopt the technology.
"Sometimes they laugh and say, 'It looks like a smile,' " he said. "Kids are decorating them. They're hanging from trees and inside houses."
The study is now being peer reviewed but was publicly released because the World Health Organization is encouraging researchers to share their findings quickly due to the health emergency caused by Zika.
Editor's note. An earlier version of the article included an incorrect reference to the funding of the study.