I’m hanging out at the park while my preschooler blows bubbles or plays in the sandbox with his friends. The sun begins setting and I’m beginning to notice the prick and the itching that arises on my skin. Everyone is having a fun time, unbothered by those pesky mosquitoes swarming around. Why am I the only one that’s getting eaten alive?
To answer this question, let’s take a look at the skin microbiome.
(I noticed a little blurb about this topic in one of my favorite newsletters, Your Local Epidemiologist and I had to dig in further!)
A person’s unique skin microbiome can attract mosquitoes
Mosquitoes use many cues to find their next host – heat, carbon dioxide, visual cues, and a vast array of molecules that attract them to their next meal. One source of these molecules is the skin microbiome, the microbes that live on the skin.
Research published in the early days of next-generation sequencing looked at how the skin microbiome could influence whether mosquitoes were more or less attracted to certain people. For the study, Niels Verhulst and colleagues studied microbes and odors from 48 volunteers by giving them nylon socks to wear for 24 hours. They also gave the participants a set of instructions for what they could or couldn’t do during this timeframe. At the end of the 24 hours, the researchers collected volatile compounds responsible for odor from the foot and sampled for bacteria on the participants’ feet and sequenced them.
By comparing these data points, the researchers found that participants who were more attractive to the mosquitoes had higher abundances of bacteria, but that the overall bacterial population was less diverse compared to those that attracted fewer mosquitoes. The team also found correlations with two common skin bacteria: Staphylococcus spp. was 2.62 times higher in those that highly attracted mosquitoes compared to those that were poorly attractive to mosquitoes and Pseudomonas spp. was 3.11 times higher in those that poorly attract mosquitoes than those that were highly attractive to mosquitoes.
Engineering the skin microbiome to repel mosquitoes
Because microbes are responsible for producing the odors in sweat that attract mosquitoes, it’s possible that identifying these odors, and the odors that repel them, could help develop mosquitoes repellents.
To see this work in action, we turn to research from Omar Akbari’s group published in 2024. This work looked at reducing the amount of lactic acid bacteria produced. Lactic acid is a well-established attractant for mosquitoes and is produced in the bacteria Staphylococcus epidermidis and Corynebacterium amycolatum. The team engineered these bacteria to produce less lactic acid by deleting their lactate dehydrogenase gene. They applied these bacteria to the skin of mice by dipping a swab in a culture of the engineered bacteria and painting it onto exposed skin on mice 15 times over three consecutive days. At the same time, the researchers did the same study set up using wild-type S. epidermidis that produced lactic acid.
The researchers found that the mice treated with the engineered bacterium that weren’t producing lactic acid had reduced levels of mosquito attraction and feeding that lasted 11 days. On the other hand, mice treated with the wild-type S. epidermidis made the mice more attractive to mosquitoes because of the lactic acid they produced.
This finding is interesting on a practical level if you compare it to current mosquito repellent technologies. The common repellent DEET lasts 4-8 hours, which becomes impractical for areas impacted by malaria, dengue fever, and other mosquito-borne illnesses. Frequent application can become both logistically and cost prohibitive. However, DEET boasts a >90% reduction in mosquito attraction. The authors of this study mention that their method reduces attraction by 55.3-68%, but since it lasts longer, there is a trade off.
Is a microbiome-based mosquito repellent in our future?
I’d be interested to see what follow up studies come out of this. Alongside reducing lactic acid levels produced by skin bacteria, could engineering the same bacteria to produce more molecules that repel mosquitoes help? Or what about simultaneously reducing the levels of other molecules mosquitoes are attracted to? The researchers also published another paper that same year that looked at other volatile molecules from bacteria and how they affect mosquito landing. Also, how long will a microbiome-based insect repellent last? The study above suggests 11 days but this was after a three day period with multiple swabs a day. A few years ago, I wrote a news story about engineering bacteria to deliver drugs to the skin. They found a similar finding – the bacteria stayed on the skin much longer than current topicals.
While mosquito bites feel like a minor nuisance, in the context of the global rise in mosquito-borne illnesses, repelling mosquitoes has real public health consequences. I’m excited to see what new solutions are out there beyond short-lived sprayed repellents and whether microbiome-based strategies can give a more long-term effect.
Further reading
- Composition of Human Skin Microbiota Affects Attractiveness to Malaria Mosquitoes. PLoS One. 2011.
- Engineered skin microbiome reduces mosquito attraction to mice. PNAS Nexus. 2024.
- Identification of human skin microbiome odorants that manipulate mosquito landing behavior. Scientific Reports. 2024.
- Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles. Insects. 2023.
- Vector-borne Diseases. American Mosquito Control Association
Featured image source: NIAID