In 1965, Fay and Perry were studying the ovipositional preferences of Aedes aegypti at the Communicable Disease Center (now the Centers for Disease Control and Prevention). Their 1965 and 1966 publications outlined what would eventually be known as the CDC Ovitrap, used in hundreds of experiments around the world. The study compared clear glass beakers to beakers that had been painted black and found that the mosquitoes preferred the darker beakers. Another experiment published in the same paper showed an ovipositional preference for solutions that had been darkened with food dye. There was no statistically significant difference between red, green or brown dyes as long as they darkened the water in the trap.
Surfaces for Oviposition
As discussed previously, Aedes mosquitoes do not lay eggs directly in the water. They prefer to oviposit on a moist surface near the water line. In some cases, this could be the wall of the trap itself. This is very inconvenient, as the trap wall is a large surface area that would be difficult to study (in surveillance scenarios) and sanitize (in all scenarios). Fay and Perry tested medical tongue depressors as an oviposition pad in their ovitraps. Both uncovered tongue depressors and ones covered in various materials were tested. The results showed a preference for tongue depressors covered in brown blotting paper were strongly favored.
Studies that are more recent have found that many porous materials in dark or natural colors are effective oviposition sites for ovitraps. An ovitrap can use seed germination paper, Pellon paper, brown blotting paper, cardboard or wood with much the same effect. While there is bound to be an ideal substrate for egg collection, current Zika efforts are largely focused on impoverished regions where some materials may be inaccessible. In these situations, it is more important to find something that will work and can be deployed quickly and cheaply than seeking a way to get the ideal substrate delivered to a hot zone.
The same logic can be applied to the rest of the ovitrap; it is far better to deploy a trap with an old dirty bucket today than waiting for a shipment of expensive specialty containers. Many of the areas where Zika is spreading already suffer from a lack of public health funding, and claiming that a costly solution is the only measure that will work is counterproductive. Community involvement is by far the most important resource in these cases. A trap that is deployed but not maintained only serves to give the mosquitoes one more artificial breeding site – when 15 minutes twice per week can prevent any new mosquitoes from emerging at a given household.
Program Manager for Biomedical Engineering
Eagle Medical Services, LLC