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Sunday, August 7, 2011

Health News: DOST "OL Mosquito Trap": The Science of Mosquito Control and Dengue Prevention

According to the Department of Health (DOH), dengue incidence in the Philippines has risen to an “all-time high” and reached the epidemic proportion in some regions.

In 2010, DOH recorded 98,934 dengue cases with 644 deaths from January to September alone. The cases have doubled compared to the entire 2009 cases with a total of 57,819.

This is the reason why DOH concluded that 2010 is the year of living “dengue-rously,” where dengue took center stage as the most prevailing health issue in the country.

The World Health Organization (WHO) considered dengue as one of the fastest-emerging infections in the world that, despite decades of research, there is no effective drug or vaccine ever developed.

Meanwhile, the Department of Science and Technology (DOST) introduced an alternative to address the alarming dengue situation in the country. This is the DOST Ovicidal and Larvicidal (OL) mosquito trap, a low cost yet effective device designed to reduce the population of the dengue-carrying “Aedes aegypti and Aedes albopictus” mosquitoes by attracting and killing their eggs in a simple but effective science-based system.

Dr. Lilian de las Llagas, OL trap technical consultant and mosquito expert from the College of Public Health, University of the Philippines Manila (UPM) said that, “In order to appreciate how OL mosquito trap works and understand how dengue virus spreads, it is important to understand the life cycle of the female dengue-carrying Aedes mosquitoes.”

Basically, female mosquito has three major chores: To mate with the male mosquito, sip blood of human victim and lay eggs.

“When we talk about the transmission of dengue virus, male mosquito has no significance at all except for reproductive purposes,” said Dr. de las Llagas. After mating with the male mosquito, female mosquito starts to hunt a human victim to supply her blood meal from sunrise to sunset. “This is the reason why dengue virus is not transmitted after six o’clock because Aedes mosquito bites only at daytime,” added Dr. de las Llagas.

Dr. de las Llagas warned that among the favorites of mosquitoes are children who are smelly and wet with sweat, but this does not mean that mosquitoes are selective. No one is exempted from mosquito’s bites. A female mosquito needs to bite at least three human victims in order to complete her blood meal. This leads to virus transmission. Every time an infected mosquito bites, it transfers the virus.

When blood meal is satisfied or completed, the female mosquito lays her eggs. This is the time the OL mosquito trap performs its functions to impede mosquitoes’ regeneration.

The OL mosquito trap system is designed to attract female mosquitoes to lay its eggs on the trap. Basically, the black paint or black container lures the female mosquitoes. Also, the strip of wet “lawanit” board inside the trap creates optimum condition that adds up to the level of attraction for female mosquitoes.

The scientific principle behind this technology is that mosquitoes preferred to lay their eggs in dark colored containers. “This is not actually a new technology,” said Dr. de las Llagas. “This fact has been known since 1969.”

What is new about the OL mosquito trap is the natural ovicide and larvicide incorporated to the system. These are pellets in form, made from organic compounds derived from plants. These pellets contain non-toxic substances safe to human. However, when they are incorporated to the system they become ovicidal and larvicidal. The word “cidal” connotes death. “So once the egg touches the solution it will die. If the egg hatches, the larvae will die, its larvae will not become pupa, its pupa will not become adult and no adult to lay eggs,” said Dr. de las Llagas.

The technology is also easy to manage. It is a “set and forget” principle. Set the trap, put it on dump and undisturbed areas or in the suspected areas where mosquitoes are hiding, then forget about it, because the trap itself kills the eggs or the larvae.

If a single female mosquito lays 100 eggs in the trap, this means you trap 100 eggs to become adults in several days, and you prevent 100 mosquitoes to bite approximately 300 human victims at the average of three human victims in every complete blood meal. “It is a simple arithmetic in terms of natural mosquito reduction by simply putting this trap. The more traps, the better,” said D. de las Llagas.

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