Who would have thought a simple mosquito could cause so much trouble? As the Olympic Games begin in Rio de Janeiro, there is a lot of concern regarding the transmission of infectious diseases like the Zika virus. Over the next two months Eagle Medical Services will publish an episodic literature review on this topic. We will look at how ovitraps can be designed to control the population of adult Aedes genus mosquitoes, limiting the spread of these disease vectors.
Mosquito Breeding Behavior
Aedes aegypti and Aedes albopictus mosquitoes serve as vectors for multiple infectious diseases including but not limited to; dengue, yellow fever, West Nile fever, chikungunya and Zika virus. Both species can be found in tropical, subtropical and temperate climates, with Ae. albopictus being more tolerant of low temperatures. As a result, Ae. albopictus can be found in more moderate areas of the US where Ae. aegypti would not be able to thrive. Ae. aegypti prefers to collect its blood meals from humans and is therefore typically found in urban areas. Ae. albopictus feeds on both animals and people and prefer an environment with more vegetation.
When seeking a breeding site, these mosquitoes tend to seek pools of stagnant water. These pools form anywhere water is allowed to collect, including both natural and artificial containers such as buckets and discarded tires. Mosquitoes of the Aedes genus lay their eggs (oviposit) on a moist substrate just above the water surface.
An adult Aedes mosquito will collect a blood meal from a mammal before seeking a site to oviposit. An uninfected mosquito may be infected when feeding on a human that is infected with the Zika virus. It is not yet clear whether the mosquito can be infected with the Zika virus in the larval or pupal stages. Once the mosquito has acquired a blood meal, it may seek a suitable place to oviposit its eggs. Depending on the amount of blood collected the mosquito may perform multiple feedings before the eggs are mature and ready for oviposition. The mosquito can only transmit the Zika virus while feeding on a person.
Ovitraps are artificial containers designed to simulate the preferred breeding sites for container-breeding mosquitoes. They use a porous material attached to the side of the trap, partially submerged so that the material gets wet. Materials such as cardboard, Pellon or seed germination paper can be used. Ovitraps were originally designed as a surveillance tool, making it easier to collect eggs and monitor Aedes populations. However, with the use of lethal ovitraps and frequent collection schedules, ovitraps can be used as a measure to help control the population of adult Zika vectors. For more information, please see Dr. Ulibarri’s article in F1000 Research.
Attraction and Stimulation
There are two properties of a compound that may increase the number of eggs laid in a trap. An attractive compound entice gravid mosquitoes to travel towards the trap, increasing the number of visitors to the site. An oviposition stimulant encourages the gravid mosquito to oviposit in the trap. Attractants tend to have a long range, while stimulants often only work when the mosquito is in direct contact with the solution. Some compounds also have the opposite effects, deterring mosquitoes from entering the trap or repulsing them from ovipositing. A single compound may have both attractant and stimulant properties, but few studies have made an effort to separate these properties when evaluating a specific plant, bacteria or compound. To reflect this lack of specificity we will refer to compounds only in terms of increasing or decreasing oviposition preference.
Program Manager for Biomedical Engineering
Eagle Medical Services, LLC