Pestology Blog

The Lethal and Sterile Doses of Gamma Radiation on the Museums Pest, Varied Carpet Beetle, Anthrenus verbasci (Coleoptera: Dermestidae) 

Gamma radiation is what turned Bruce Banner into the hulk- so when I found this article, I immediately had to see what it could do to carpet beetles. Much to my initial disappointment, I learned it did not turn them large mean and green, but I digress.  

To get ourselves situated, beetles in the family Dermestidae are commonly called carpet beetles. Carpet beetles are common household pests, often being found in carpets as their name suggests. Outside of a regular home, these pests are particularly destructive in museums. The artifacts held in museums from papers, fabrics, taxidermy, and many other organic materials, are under consistent threat from these beetles. Think of all the priceless history we keep not only on display, but archived away for the future. The larvae of these destructive beetles will eat away organic material, and over time can completely destroy critical items that preserve the world’s cultural heritage.  

Carpet beetles, like many stored product pests, can have a long life cycle, taking even a few years to go from egg to larvae to adult.

The priceless artifacts of museums cannot be exposed to many products the structural pest management industry would usually use. The fragile nature of the artifacts, many of whom cannot be cleaned or have delicate chemical balances, prevent use of almost every product at a PMP’s disposal. Now as you know, PMP’s have more tools to use than just insecticides. In this case, there are other IPM options to control carpet beetles. One of these options that is emerging is gamma radiation. 

Gamma radiation must be very specifically measured to be implemented in only the dosage necessary for the life stage being targeted. The dosages are often measured in a unit called kilograys. The goal of the research was to determine the lethal and sterilizing doses of radiation specifically for the varied carpet beetle. Note that different species have different dosages needed, making this pest specific research necessary.

The researchers reared the carpet beetles in the lab and took groups of each life stage to test against the radiation. They took each group and exposed them to a period of radiation at 5 different levels. Radiation exposure was done in an enclosed machine to keep the personnel involved safe from the radiation. In parts of the experiment, the irradiated adults were mated to see the viability of their eggs.  

As you might expect with the larvae, there was a significant positive correlation with higher radiation killing more of them. The larvae also became increasingly deformed with higher radition. Radiation reduced pupal emergence but did not deform the adults. At higher levels the pupa did not emerge and instead disintigrated internally.  

The younger the beetle, the more sensitive it was to radiation which follows the established trend that the less differentiated the cells in an organism are, the more susceptible it is to radiation. So the most differentiated cells are in adults and those are the least sensitive to radiation needing 1 kilogray to get to 100% mortality in three weeks. Even younger pupae were greatly affected, but older pupae were less so as they were more differentiated.  

The takeaways here were that the sterilizing dose and lethal doses discovered could be a viable option for killing these pests. The sterilizing dose would prevent future larvae and when needed the lethal dose would kill all of them.

Now with all that being said, one thing you may be thinking is "How safe is this to perform or administer?" Well, the device that irradiates the samples also encloses them so that the radiation isn’t getting out to everyone nearby. In the context of museum pests, if you had an infested artifact, the idea would be potentially put the artifact in a radiation chamber leave it there for whatever time is needed for the beetles to die. and then wait till the artifact is safe again. Basically, this method, when regular precautions are taken, would not pose a risk to personnel involved.

Article by Ellie Lane, BCE-Intern

References

Hamza, A., Zahran, N. & shafeay, N.E. The lethal and sterile doses of gamma radiation on the museums pest, varied carpet beetle, Anthrenus verbasci (Coleoptera: Dermestidae). Sci Rep 13, 16984 (2023). https://doi.org/10.1038/s41598-023-43739-x 

Identification of the Pan-allergen Tropomyosin from the Common Bed Bug (Cimex lectularius)

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

Scuttle Fly Megaselia scalaris (Loew) (Diptera: Phoridae) Endoparasitoid as a Novel Biocontrol Agent Against Adult American Cockroaches (Periplaneta americana)