How to kill Zika mosquitos with old tyres
Hitting mosquitos where it hurts – their eggs – is one way of controlling pesticide-resistant insects. Now North and Central American scientists have come up with an efficient egg trap – with the added bonus of breathing new life into discarded tyres. Belinda Smith reports.
A simple, cheap trap made from old tyres is seven times more effective at snaring mosquito eggs as a commercial device.
The trap, tested last year in Guatemala, is particularly effective against Aedes aegypti mosquitos, which carry the Zika virus along with dengue and yellow fever. The work has been accepted for publication in F1000Research.
Pesticides have long been the method of choice when it comes to controlling pesky mosquitos. But resistant mosquito populations are surging, and pesticides often kill bats and dragonflies – both of which prey on mosquitos and their larvae.
So Gerardo Ulibarri from Laurentian University, Sudbury, Canada and colleagues from Mexico and Guatemala decided to use a mosquitos' favourite breeding ground: old tyres.
"Partly because tyres already represent up to 29% of the breeding sites chosen by the Aedes aegypti mosquitoes, partly because tyres are a universally affordable instrument in low-resource settings, and partly because giving old tyres a new use creates an opportunity to clean up the local environment," Ulibarri says.
They salvaged discarded tyres and got to work, cutting two 50-centimetre lengths and stacking them together like a mouth.
The bottom section contained a mosquito-attracting liquid and two floating "landing strips" for mosquitos to lay their eggs. A valve below drained the fluid so it could be filtered and reused – handy in areas with little clean, fresh water.
Some 84 of these "ollivantas" were hung around the town of Savaxche in Guatemala for 10 months from February 2015, along with 84 standard "ovitraps" – essentially black buckets filled with fluid.
The traps were checked twice a week during the warmer months from June to October and once a week during the low season. The egg papers were removed and after the eggs were counted, were burned or destroyed with ethanol.
The researchers found the ollivantas trapped more than 180,000 eggs over the 10-month period, whereas the standard traps caught just 27,000.
Along with community and health worker education to dispel myths, such as mosquitos only breed in natural ponds and that tending house and garden are women's jobs only, the researchers write: "our project provides evidence for a promising alternative to harmful pesticides and standard ovitraps at a time when the threat of viral outbreaks is increasing.
"By incorporating ecology and community-oriented elements, this alternative has the potential to be effectively scaled up and be sustainable."