In 2025, the Global One Health Academy offered Postdoctoral Support Awards to accelerate postdoctoral research in One Health at NC State. Charles Kwadha, Ph.D. was a recipient of the 2025 Postdoctoral Support Awards for a project on olfactory-mediated behavior of bed bugs. He has since moved on from NC State and is now a researcher at the Norwegian Institute of Bioeconomy Research (NIBIO). Learn more about Dr. Kwadha and how the Global One Health Academy helped support his research on detection and treatment of bed bugs through his featured spotlight below!
What did you study for your postdoc at NC State? What/who inspired you to pursue this field of study?
I am an insect chemical ecologist, interested in understanding how insects use scent to communicate between themselves and to find food. This is quite important because we can use that knowledge to manage insects that damage crops as well as those that transmit diseases to humans and animals. During my time at NC State, I worked in Coby Schal’s lab in the Department of Entomology and Plant Pathology. Schal lab studies Urban Entomology with main focus on cockroaches and the common bed bug that impact people in indoor environments and explores sustainable methods of managing the pests. I specifically was studying the behavior and chemical ecology of bed bugs, identifying and optimizing scent components from their blood hosts. Managing bed bugs is a challenge, one way to go around this is to get better lures to improve detection and trapping systems.
Growing up in Kenya, especially during my high school days, I came across articles in the local newspapers about the late Thomas R. Odhiambo who is the founding director of the International Center of Insect Physiology and Ecology (icipe) and became interested in Entomology. As an undergraduate student at the University of Nairobi, I selected entomology courses where I was introduced to the concept of insect communications and how chemical cues are such a significant language in the insect world. Picture a bee hovering or approaching a flower, there could be two reasons for this: 1) The bee is attracted to the color of the flower or 2) The flower or microbes associated with it are releasing some chemical compounds to attract the pollinator.
What are the implications of your research, and how does it fit into the One Health framework?
As we know, bed bugs have a lot of implications for human health. In addition to the discomfort, bites cause allergic reactions. Some people experience psychological trauma and anxiety. Accumulation of bed bug waste contaminates the air in our houses posing a grave health risk. Not only are they a nuisance for humans, but they also can infest poultry farms, causing allergic reactions and in severe cases reduction in egg production. The close ties between bed bugs, chickens, and humans, and the health risk that hinges in that association certainly fits under the One Health framework as it impacts people, poultry, the environment (through use of pesticides for control), and overall productivity.
How did GOHA’s support help advance your One Health related research?
GOHA gave us financial support to test the question, “Human or Chicken odors?” in which we wanted to find out whether bed bugs have a preference between human or chicken scent. To obtain chicken swabs, I collaborated with Dr. Rocio Crespo and Rebecca Wysocky from the NC State College of Veterinary Medicine (CVM) and Dr. Kenneth Anderson from the Prestage Department of Poultry Science (CALS). Once we had chicken and human swabs, we presented them to bed bugs in a Y-tube platform. The platform has two-arms which makes it possible for us to present bed bugs with two choices. First, we presented chicken swabs vs control, then human swabs vs control, and then chicken vs human swabs. From the preliminary results, we found that chicken scent attracts bed bugs, similar to human scent. When it comes to preference, we observed a change of preference depending on the type of experiment and platform used. However, these findings are not conclusive and require additional experiments to validate it. As we were doing these tests, we came up with a new question, “Could scent components identified from chicken plus human scent be more attractive to bed bugs than components identified from human scent alone?” We don’t have an answer yet, but we are observing some promising trends. Right now, the Schal lab is working on optimizing identified scent compounds to help design effective traps for use in both human and animal settings.
Another activity that was made possible through GOHA’s support was a trip to Yale University where I visited Dr. John Carlson’s lab, which studies mechanisms (receptors, neurons, and circuits) used by insects to sense scent. I also had the opportunity to present my research, “Navigating the odorscape: Effects of physiological status on bed bug odor preferences,” at a mini-symposium organized by Dr. Carlson. I had a stimulating interaction with Dr. Carlson and members of his lab as well as Dr. Emmanuelle Jacquin-Joly and her lab members, from INRAE-France, whose visit overlapped with mine.
Additionally, I was able to collaborate with Dr. Chris Hayes and Dr. Ayako Wada-Katsumata which led to a publication, “Bed bug preferences for host odor or aggregation odor are differentially modulated by physiological state in various odorscapes,” published in the journal of Pest Management Science. In this publication, we showed that hungry bed bugs are more likely to go where human scent is coming from (as they associate the scent with food). However, those that recently fed on blood find human scent unappealing and instead are interested in another type of scent called aggregation scent, coming from their hiding places.
The final activity made possible through GOHA’s support was my mentoring of Sage Wieck, an undergraduate student currently in her third year, pursuing a zoology major with a minor in entomology. Sage has a keen interest in the interaction of bugs and birds. This was a perfect opportunity for her to get introduced into bed bugs’ behavior and chemical ecology. During the mentorship, Sage impressively mastered the art of handling and testing bed bugs. She is running additional experiments to finalize the project. We are really happy that she is still interested and is actively involved in the project.
What are you doing currently? How do you incorporate One Health into your current career?
In November 2025, I moved to Norway where I am currently working at the Norwegian Institute of Bioeconomy Research (NIBIO) as a research scientist. In my new position and together with the team, we identify and develop safe alternatives to pesticides that growers can use to manage agricultural pests. Our research focuses specifically on greenhouse pests, such as aphids and mites, which aggressively attack vegetable crops. Commonly used synthetic pesticides are detrimental to both human and environmental health. Therefore, our main goal at NIBIO is to find more sustainable methods to mitigate pest populations while improving overall crop, environmental, and human health.
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