From a human perspective, the Aedes aegypti mosquito is a seriously nasty beast. Even before the Zika virus became a terrifying threat to pregnant women in tropical areas, Ae. aegypti was spreading dengue, yellow fever, and chikungunya, in addition to causing plenty of sleepless nights. So the announcement of a cheap, effective trap is good news indeed.
The combined death toll of all the diseases Ae. aegypti spreads does not match the malarial toll of Anopheles gambiae. Nevertheless, it's a strong candidate for the animal species the world could best do without.
Part of the reason Ae. aegypti is such a menace is its fondness for small manufactured containers of water as sites to lay its eggs. Disused flowerpots or old tires are perfect, and as the numbers of such discarded objects have boomed, Ae. aegypti has come to love living in cities, feeding on humans to nourish its eggs.
Dr. Laura Harburguer of Argentina's National Scientific and Technical Research Council decided to turn the tiny vampires' strength against themselves, creating traps that would attract them, but prevent the appearance of the next generation.
We're coming for you, spawn of the devil. Mrfiza/Shutterstock
In the Journal of Medical Entomology, Harburguer describes the use of a cup made of polyethylene infused with pyriproxyfen, a larvicide that permeates any water the cup is holding.
To be effective the trap needs to prevent the development of the larvae of the mosquito, while also not causing the mosquito mother to lay the eggs elsewhere.
The paper describes 100 percent success over 30 weeks on the first goal, but this was achieved in a laboratory experiment that didn't test whether mosquitoes would use the cup in an environment where other choices were available.
Ovitraps, as cups designed to attract mosquito eggs are known, have been in use for decades both to monitor the presence of mosquito species and to keep numbers down. Harburguer's innovation was to combine pyripoxyfen with low-density polyethylene, which the paper describes as an “effective, inexpensive and low-maintenance tool for Ae. Aegypti surveillance and control.” One of the advantages of the combination is that the trap remained potent even after twenty washes.
A potentially particularly useful aspect of the idea is that, as the paper noted, “Female mosquitoes can acquire pyriproxyfen crystals when landing on a treated surface and then transfer them to breeding sites, thereby killing larvae in these sites.” Ae. Aegypti likes to lay small numbers of eggs at multiple sites, so are particularly likely to spread the poison around in this manner, although once again the effectiveness of this has yet to be tested outside the lab.
The timing of publication is doubly significant. Besides the alarm about Zika, the paper's release coincided with the announcement in EbioMedicine that global warming is allowing Ae. aegypti to spread into Europe, raising the possibility of outbreaks of dengue and the other diseases this winged horror carries.