While touring a hospital in India, Penn State entomologist Matthew Thomas recalls walking past the intensive care unit and seeing a young boy—about 14-years-old—severely ill from malaria. He learned later that the boy had died the following day, and the unfortunate circumstance of it all stayed with Thomas. If the boy had been bitten by any other mosquito, he may not have died.
An underlying theme of Thomas’s career has been to address the question of what makes a pest a pest, and what can be done about it. Having witnessed the impact of malaria firsthand, and having been infected twice himself, the pest that Thomas thinks most about these days is the malaria mosquito, and he is currently working with an international team of researchers to implement a practical solution to what is considered to be one of the more severe public health problems worldwide.
Matthew Thomas, professor, College of Agricultural Sciences; Huck Scholar in Ecological Entomology
Huck Institutes of the Life Sciences
Center for Malaria Research
“I’m still driven to understand basic research questions, such as how environmental factors influence the distribution of malaria. But, it was obvious from being in Africa and having malaria that this is a pressing problem. Ultimately, it’s what we are going to do about it that motivates me the most.”
According to the Centers for Disease Control and Prevention, an estimated 445,000 people died of malaria in 2016—most were young children in sub-Saharan Africa. The cost of malaria in nations most impacted, including those in tropical and subtropical areas of the world, is enormous. While 70 percent of all malaria cases and deaths were concentrated to eleven countries—the majority of those being in Africa—the goal is to come up with solutions for wide-scale prevention in the hopes of staving off the potential spread of the disease.
Thomas, professor and Huck Scholar in Ecological Entomology, along with collaborators in Europe and Africa, have received a five-year, $10.2-million grant from the Bill & Melinda Gates Foundation to investigate a method for preventing the transmission of malaria. The method involves limiting mosquito access to houses by blocking openings and installing “eave tubes” that contain a unique type of insecticide-laced mosquito netting developed by Dutch partner In2Care that kills the insects as they attempt to enter.
“The use of insecticides to control mosquitoes has saved millions of lives, but this tactic is increasingly challenged because mosquitoes quickly evolve resistance to the very limited number of insecticides currently used in public health,” said Thomas. “The eave tube approach presents a novel strategy to help combat this challenge by simultaneously making houses more mosquito proof and providing a novel way of delivering insecticides, which creates opportunities for using a wider range of insecticidal products.
In Africa, mosquitoes have a strong preference for entering houses at night through eaves—the gaps between the roofs and the walls of houses. Many residents leave the eaves open to promote airflow and to cool their homes at night. The team’s novel eave-tube approach involves blocking the eaves and inserting tubes that act like chimneys to funnel human odors to the exterior of the home.
“The eave-tube approach presents a novel strategy to help combat this challenge by simultaneously making houses more mosquito proof and providing a novel way of delivering insecticides, which creates opportunities for using a wider range of insecticidal products.”
Attracted to the human odors, mosquitoes enter the tubes and encounter netting that has been treated with a coating that binds insecticidal particles to it. The netting can hold several kinds of powdered insecticides, including biological agents.
“The small amount of insecticide used in the tubes means that it is cheap to treat an entire house,” said Thomas. “Furthermore, retreatment is easy, as it requires simple replacement of small pieces of netting within the tubes.”
As an in-home solution, the eave tubes offer an elevated, yet simplified approach to malaria transmission prevention to complement the use of bed nets. While insecticide-treated bed nets are an excellent tool, Thomas explains that not everyone has access to one, they can become damaged, and they put the impetus on the individual to protect themselves. By offering a preventative solution at level of the household, Thomas hopes to add to the impact.
“Many global efforts have led to a marked reduction in malaria over the last fifteen years. We want to build on this momentum by offering new tools that can be put into place in the short term to help deal with the problem of insecticide resistance.”
“Eighty percent of transmissions happen at night when people are in their homes, so if you could stop mosquitoes from getting into the house then you will have taken personal protection to the level of the household,” Thomas said. “Equally, if you could kill mosquitoes at the level of the household then you can get this community benefit by stopping mosquitoes from coming back the next day or flying next door. That’s what is different about this technology. You just go to bed and you’ll be protected.”
Implementing the Solution
As part of a $5.6 million grant from the European Union, the research team developed initial prototypes and conducted proof-of-concept studies in semi-field and field settings in the Kilombero valley in southern Tanzania. This work was also supported in part by the USDA National Institute of Food and Agriculture and Hatch Appropriations.
The current project funded by the Bill and Melinda Gates Foundation expands on this work by installing eave tubes in approximately 3,000 homes in villages in Cote d’Ivoire, as well as a number of smaller-scale pilot studies in Tanzania. The researchers are examining householders in these villages and comparing them with equivalent control villages that have not been supplied with eave tubes to determine the effect of the intervention on malaria incidence. The team is also testing the mosquitoes caught in the villages for insecticide resistance. In addition to the entomological and epidemiological studies, researchers are also conducting socio-economic analyses to determine homeowner acceptance and create strategies for implementation across different regions and market sectors.
“That’s what is different about this technology. You just go to bed and you’ll be protected.”
“Our primary goals for this phase of the project are to demonstrate the health impact of eave tubes, and to build the foundation for commercialization and wide-scale implementation of the tubes,” Thomas said. “Many global efforts have led to a marked reduction in malaria over the last fifteen years. We want to build on this momentum by offering new tools that can be put into place in the short term to help deal with the problem of insecticide resistance. This is what eave tubes offer.”
This work is occurring at an opportune time, explains Thomas, as many African nations are focusing on housing development in anticipation of increased populations over the next several decades.
“This is an opportunity to ride the wave of urbanization and a growing economy in Africa,” Thomas said. “We can utilize the fact that people are already improving their houses, and we can do something to make that house even better by offering a level of protection to the homeowner and their neighbor, which in turn will benefit the community as a whole.”
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