Malaria Transmission Significantly Reduced Using Human Odor-Baited Traps

The use of a newly developed mosquito trap incorporating human odor has resulted in a 70% decline in the population of the most significant malaria mosquito on the Kenyan island of Rusinga. After the introduction of the odor-baited traps on the island, the proportion of people with malaria was 30% lower among those living in houses with a trap compared to people living in houses who were yet to receive a trap.

In the war against malaria, there are numerous fronts on which the battle to prevent disease transmission take place. Vector (mosquito) control is an area that has seen its share of limited success over the years, mainly through the use of insecticides such as DDT. However, resistance to many insecticides has forced investigators to search for alternative methods of controlling insect populations and reducing transmission rates of disease-carrying mosquitos.

Now, a collaborative team of researchers from Wageningen University in the Netherlands, the Kenyan International Centre of Insect Physiology and Ecology (ICIPE), and the Swiss Tropical and Public Health Institute (Swiss TPH) have developed a new mosquito trap that incorporates human odor. It has resulted in a 70% decline in the population of the most significant malaria mosquito on the Kenyan island of Rusinga.

Amazingly, after the introduction of the odor-baited traps on the island, the proportion of people with malaria was 30% lower among those living in houses with a trap compared to people living in houses who were yet to receive a trap.      

“The objective of the trial on Rusinga Island in Lake Victoria was to investigate whether malaria mosquitoes can be captured and destroyed using traps with a lure so that the risk of new malaria infections is minimized,” explained senior study author Willem Takken, Ph.D., professor of medical and veterinary entomology at Wageningen University. “Ultimately we want to eradicate malaria completely, in an environmentally friendly and sustainable manner. In the case of extensive use of insecticides to kill the mosquitoes which are the carriers of the disease, the mosquitoes become resistant to the chemicals.”

This infographic shows how the odor-baited traps catch malaria mosquitoes and lower the general mosquito density in the area. [Wageningen University]

“That makes combating malaria increasingly tricky and less environmentally friendly,” Dr. Takken continued. “Alternative methods are therefore urgently needed. As we use a natural lure—namely human odor—in our approach there is no negative impact on the environment, and it is very improbable that the mosquitoes will become 'resistant' to being captured. After all, the mosquitoes need their attraction to the lure in order to be able to survive.”

The findings from this new study were published recently in The Lancet in an article entitled “The Effect of Mass Mosquito Trapping on Malaria Transmission and Disease burden (SolarMal): A Stepped-Wedge Cluster-Randomised Trial.”

The success of the new malaria control approach lies in its combinatorial strategy of using the odor-baited traps with mosquito nets, antimalaria drugs, and a solid social strategy. The traps require electricity to operate, but there is no central power supply on Rusinga, an island in Lake Victoria, so solar panels were installed on the roofs of homes. These not only provided electricity for the mosquito traps but also provided the homes with power for light and to charge a mobile phone. The use of solar energy to control malaria gave rise to the project name: SolarMal.

Thanks to this combined approach, all 25,000 inhabitants of Rusinga participated in the study. When the odor-baited traps are used, the use of insecticides to combat the mosquito population can be minimized—avoiding any harmful side effects of such products. The Wageningen antimalaria approach, therefore, has had not only benefits in reducing the spread of malaria but also had positive effects on the living conditions of the population.

While the mortality rate due to malaria infections—especially in children under the age of five—still rank the disease as one of the leading causes of death worldwide, it is the morbidity associated with malaria that often gets overlooked, costing Africa $12 billion a year in health-care costs and lost productivity, particularly in the agricultural sector.  

“The effect of the disease on agricultural production is hugely underestimated,” Dr. Takken noted. “As children with malaria need access to hospital care, their parents cannot work on the land and as a result food production rates decline. If those parents themselves also suffer from malaria infections four or five times a year, they are also not able to work for around 6 weeks. In such cases, extra labor needs to be brought in, or the crop will be lost. An African household loses 10% of its annual incomes through malaria. It is for good reason that reducing the prevalence of malaria was included in the ten-millennium development goals formulated by the UN.”

The World Health Organization (WHO) is aiming to eradicate malaria by 2030. To that end, investments are being made in the development of vaccines against the parasite and in combating the vectors of the parasite: the mosquitoes. The odor-baited trap—dubbed the Suna trap—represents an efficient and safe solution in the fight against the mosquito.