Thanks to their thirst for human blood, the common bed bug is a well-known and despised indoor pest. Despite the fact that bed bugs feed on humans, scientists have historically kept common bed bugs low on the public-health-pest most wanted list because they are not known to carry any pathogens like ticks or mosquitoes can. But, researchers out of the University of Kentucky have spent the last few years researching other ways that bed bugs might threaten human health much in the same way that cockroaches and dust mites can.

 

 

Over the past few years, Zach Devries and his research team have been slowly chipping away at unraveling some mysteries surrounding the potential negative health impacts of chronic exposure to bed bugs. His lab has played an important role in elevating the importance of bed bugs as public health pests. The most recent publication to come out of the Devries lab by Johnalyn Gordon and Zach Devries that I’m covering here brings us one step closer to understanding exactly how bed bug exposure can have negative clinical effects. And it all has to do with tropomyosin.

Tropomyosin is a protein found in all animal life. But invertebrate tropomyosin is found to cause an allergic response in humans. Notably, allergic responses have been documented to tropomyosin from indoor pests such as cockroaches and dust mites. What’s more interested is that invertebrate tropomyosin can lead to a process known as “cross-reactivity” where exposure to tropomyosin from one source such as an insect, can potentially trigger a similar immune response from a different invertebrate source…such as shellfish. To oversimplify, someone with a shellfish allergy could potentially exhibit a similar allergic response if exposed to other invertebrate tropomyosin sources.

To better understand how bed bug tropomyosin may fit into this storyline, Gordon and Devries set out to investigate the similarities between bed bug tropomyosin and other known tropomyosin allergens. They also tested how and where tropomyosin levels may occur in a bed bug infested home, by testing tropomyosin levels in bed bug bodies, feces, and cast skins. Lastly, they examined bed bug tropomyosin persistence in the environment over time. And, here’s what they found.

• Bed bug tropomyosin is highly similar to the German cockroach, the American cockroach, and some dust mites, as well as shrimp, crab, and lobster.
• Tropomyosin levels were detected in crushed up bed bug bodies (cadavers).
• Levels were detectable for up to 18 months.

As an additional part of this study, the researchers also surveyed pest management professionals on what their follow up procedures were for typical bed bug treatments and found that bed bug carcass removal isn’t typically part of the standard practice for the majority of companies.

What this all could suggest is that exposure to bed bug tropomyosin, thanks to “cross-reactivity,” could result in similar sensitivity to other German and American cockroaches, and even shellfish! Though, what exactly that sensitivity could be at this point isn’t clear. And that dead bed bug bodies could serve as a tropomyosin reservoir, like a tropomyosin-time-bomb (credit goes to Dr. DeVries for this amazing phrase), if dead insects aren’t removed after service.

We still have a lot to learn to fully understand how bed bug infestations impact human health, but this research helps to add to our depth of knowledge. Importantly, it’s starting to become clear that bed bugs haven’t historically been given the respect they deserve as more than a nuisance pest in homes. And there still may be more concerning details to come. This research also tells us that bed bug removal is likely an important final step in reducing any negative health outcomes that PMP’s performing bed bug treatments should consider adding to their service protocols.

Article by Mike Bentley, PhD, BCE

References

Gordon, J.M., DeVries, Z.C. Identification of the pan-allergen tropomyosin from the common bed bug (Cimex lectularius). Sci Rep 14, 7281 (2024). https://doi.org/10.1038/s41598-024-57877-3

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