[Bed Bug Supplement] A Genomic Approach

Pesticide resistance and repellency can be an extremely challenging aspect of the pest management profession. In many instances, it can be the difference between achieving control or going back to the account again and again. Historically, bed bugs have been known to become resistant to pesticide applications over time, which has created an ongoing challenge. Pesticide resistance cannot be predicted. The burden of proof rests with the PMP whose client is not experiencing physical sightings, bites or any accompanying allergies.

Technological advances in genomics and the development of genomic analytical technologies have facilitated a wide-scale examination of the associated genetic foundation of why bed bugs are truly resistant on a biological level. These technologies provide insight into factors that also may cause bed bugs to be repellent to certain insecticidal products. Genetics is at the core of repellency. As insects reproduce, their genetic footprint is passed along, which allows their offspring to become increasingly pesticide resistant. DNA simply changes and evolves.
 

How They Survive.

In 2013, a widespread research study from the University of Kentucky and University of Washington (Zhu, Potter et. al. 2013) identified 14 molecular genetic markers of differing bed bug species in various parts of the United States. These 14 molecular genetic markers are traits that remain constant and are directly associated with pesticide resistance. By identifying resistance factors and adaptive strategies that bed bugs use as a defense mechanism, researchers can use these findings to develop newer, safer and more targeted treatments against bed bugs.

One unique discovery found in this study was the majority of the genetic factors that provide bed bugs with a strong resistant capacity are located on the outer layer of its body. The genetic compounds identified are responsible for the formation of its exoskeleton, chitin production and thickness, and most importantly, the breakdown of pesticides and enzymes that the bed bug comes in contact with as they travel. Bed bugs can become naturally adaptive in various areas of their integument (outer layer) so that some areas develop more resistance than others. This phenomena is similar to our skin that becomes naturally calloused due to friction or burn. With bed bugs, the research consensus is pointing towards certain areas of the exoskeleton adapting by becoming harder. The enzymes contained underneath the exoskeleton are naturally becoming more concentrated and therefore provide bed bugs the ability to break down insecticides at a faster rate in newer generations. The insecticide simply cannot reach the necessary receptors within the bed bugs body to do harm. As bed bugs are increasingly exposed to an insecticide, the traits within its DNA are passed on to its offspring and the resistance mechanism becomes stronger.

Bed bugs are naturally adaptive. They have an extremely flat body (prior to obtaining its first blood meal) and their natural instinct is to hide and breed in areas close to a warm-blooded host. For example, the ability to sense carbon dioxide expelled by a human host signals bed bugs that a blood meal is in close proximity. This adaptive strategy allows the bed bug to acquire a meal and thus, receive the sustenance necessary for survival. This stems from the bed bug’s DNA, mainly an overexpression of a genetic trait that causes a chemical reaction, allowing bed bugs the ability to sense a meal or repel from danger.

Bed bugs are not logical creatures that have extensive long-term plans, but they persevere and are able to breed and harbor at an epidemic proportion. Bed bug nymphs in particular have been studied extensively. It has been confirmed that the majority of bed bug nymphs will stay closest to a blood meal since their adaptive strategy and genetic makeup dictate that they must feed to survive. To venture off prior to feeding is dangerous. Adult bed bugs, especially females, will venture off as they need to feed and reproduce. The focus on later staged bed bugs is to harbor in an ideal climate where a substantial blood meal is available in order to reproduce at an optimal rate. It is evident that at differing stages of the bed bug’s life, the DNA code it possess changes, adapts or evolves.

Dr. Fang Zhu, who led the University of Kentucky 2013 study, stated, “Every living thing on Earth has a unique set of strategies to adapt to life-threatening situations in the environment” and bed bugs are no exception. These adaptations are at the heart of what makes bed bug control from a resistance and repellency standpoint so difficult.
 

Controlling Bed Bugs.

As PMPs, we rely strongly on pyrethroid insecticides as a means of control, whether in liquid or dust form. Pesticide resistance has been offset by the use of non-chemical means, whenever necessary. These non-chemical methods have become the norm when dealing with clients who are sensitive to chemicals and are concerned about the use of pesticides within their homes or businesses.

The professional pest management industry must continue to use all of the tools at its disposal. This is the foundation of Integrated Pest Management. Today, many pyrethroids have become “stronger” in that they’ve been combined with newer products and/or formulations. Traditional variations include one active ingredient or newer formulation that have an active ingredient and a “backdoor” supplemental active ingredient that offsets the potential for pesticide resistance. The pest management industry continues to remain in a constant state of improvement, primarily in the development of broad spectrum pyrethroid products, including products containing neonicotinoids as supplemental active ingredients.

These supplemental active ingredients have once again allowed the pest management industry to achieve control on a dynamic, ever-changing pest. The question remains: Are we setting ourselves up for failure due to the evolving resistant DNA that bed bugs possess? Only time will allow a comprehensive answer to that question.
 

Are Bed Bugs Savvy?

When it comes to repellency, the push towards non-repellent products continues primarily through products of a biological or organic nature that offset the octopamine of an insect. Octopamine is a neurotransmitter, a neuromodulator and a neurohormone. It is responsible for an insect’s overall “mood,” e.g., whether it promotes aggression or regression. Octopamine also promotes certain movements, and can be interrelated to excitability, such as a “fight or flight” response within an insect. Although octopamine has not been studied particularly with bed bugs, it does warrant a further investigation into whether a shift in DNA can also cause a shift in octopamine receptors within a bed bug.

Octopamine may be responsible for the savviness of a bed bug since it controls many receptors within the insect that can ultimately lead to resistance and repellency. DNA continually evolves and can cause blockages in areas of the bed bug where insecticidal products simply cannot reach. In humans, DNA is responsible for all of our underlying characteristics and traits. With insects, it is the same and as time passes, it will show that certain insects are more developed biologically and possess a savviness to outsmart a “one size fits all” pesticide application.

With human disease research, focus has been on developing technologies that encompass the use of genetic information to assess the best form of treatment against disease. Immunology and targeted treatments are common. The genomic age is here and a push toward a targeted bed bug treatment will soon be within our grasp. Developments in targeted pheromone technology against bed bugs recently has been developed on an effective level. These pheromone advances with a specific identification method and a targeted treatment create a recipe for an advanced and highly effective bed bug treatment that can achieve long-term control. Until these technologies become a mainstay in the industry, we must continue to rely on currently available products that keep pace with resistance and repellency factors.

The author is an associate entomologist with RK Environmental Services, Westwood, N.J.