Bed bugs’ ability to withstand inbreeding and still produce healthy offspring is one of the reasons just one or two introductions into a building can soon result in a serious infestations, researchers announced at the American Society of Tropical Medicine and Hygiene (ASTMH) annual meeting. After virtually disappearing in the 1950s, Cimex lectularius, the common bed bug, has returned in a big way over the last ten years.

Bed bugs have also developed resistance to pyrethroids, a type of insecticide that used to be much more effective in controlling them.

ASTMH researchers also offered new ways of controlling these pests in apartments and houses. They say it is possible to prevent insecticide resistance. There are new compounds about that can attract and repel them, they added.

Bed bugs are blood-suckers. However, they do not transmit disease. They provoke allergic reactions, including itching and inflamed welts. They are known as pests that pose an economic and social threat to residents and owners of homes, apartment buildings, public buildings and hotels. Controlling them can be costly.

Bed bug, Cimex lectularius
Cimex lectularius, a bed bug. They don’t transmit disease, but provoke allergic reactions

Rajeev Vaidyanathan, PhD, associate director of Vector Biology and Zoonotic Disease at SRI International,said:

“New York City alone spends between $10 million and $40 million per year on bed bug control, and these numbers are repeated in other major cities across the US.

Over 95 percent of pest control agencies reported bed bugs as a priority in 2010, thus superseding termites as the number one urban pest.”

There are from ten to one hundred times more reports of infestations today in hotel rooms, apartment blocks, and family homes compared to twenty years ago, the researchers explained. Scientists are still not completely sure why.

Bed bugs are able to inbreed without compromising their genetic integrity, i.e. they can still produce healthy young – this means that you only need a few of them to start a serious infestation.

Coby Schal, PhD, and Ed Vargo, PhD, from North Carolina State University (NCSU), set out to examine the genetics of bed bugs. They performed two studies on three apartment buildings in New Jersey and North Carolina. They found that within each apartment the bugs were very closely related – there was an extremely low genetic diversity within each single building. This means that each infestation started off with a very small number of bugs. Their studies are currently being peer-reviewed.

If bed bugs are able to inbreed and still produce healthy offspring, they can spread easily from one apartment to the next in the same building rapidly.

The team carried out a separate study which looked at 21 infestations from Florida to Maine. In virtually all cases, the source was a single room within a building.

Schal said:

“Inbreeding gives bed bugs an advantage in being able to colonize. A single female that has been mated is able to colonize and start a new infestation. Her progeny and brothers and sisters can then mate with each other, exponentially expanding the population. With many organisms, extensive inbreeding would cause serious mutations that would eventually bring about an end to the population.”

The researchers added that cockroaches also appear to be successful inbreeders.

Bed bugs have become progressively resistant to previously effective insecticide treatments. A new study has shown that it is possible to neutralize the mechanism that makes the bed bug resistant to pyrethroids insecticides.

Ken Haynes, PhD, an entomologist from the University of Kentucky and team have been researching on bed bug insecticide resistance. Collaborators, Subba Reddy Palli and Fang Zhu targeted specific enzymes within the insects that are linked to the P450 detoxification system that breaks down the insecticides before they reach their targets. They used RNA interference against the P450 family enzymatic partner to selectively switch off the system inside the bed bugs, thus preserving the efficacy of deltamethrin (the insecticide).

Bed bug behavior is influenced by several compounds. Scientists say they are discovering new ones. If they can identify and understand what the functions of chemical compounds the bed bugs secrete are, they might have a better chance of controlling infestations.

Vaidyanathan and team isolated seven new bed bug compounds that had never been detected before. These could become attractants (to attract the bugs). The idea is to create a cocktail of these compounds to attract the pests into a trap.

Entomologist, Mark Feldlaufer, PhD, who works in the US Department of Agriculture’s Agricultural Research Service, is carrying out research into pheromones that can influence bed bug behavior. There are some alarm compounds that warn insects of the same species that there is danger – the team has examined their chemical blueprint.

Feldlaufer’s investigation discovered which chemicals are associated with the outer skeleton of bed bugs. He is trying to find out whether dogs might be able to sniff out some of these chemicals, i.e. sniff out bed bugs. Dogs are used by professionals in pest management to seek out pests, just as they are used to find drugs, lost people and explosives.

Vaidyanathan says:

“Bed bugs are our oldest roommates. There is even evidence of bed bugs in Pharaonic Egypt. The problems we are seeing with bed bugs in North America did not happen overnight. They are the consequence of multiple repeated introductions from all over the world.

We have the highest concentration in the history of our species of humans living in cities. For as long as we’ve been standing on two legs, we’ve lived in rural areas. Over the last ten years, the majority of humans have moved to urban areas.

This is the perfect setting for creating a high density of mammal nests for bed bugs. Bed bugs do not have wings; they are nest parasites, so our own population density has helped them to thrive.”

Within a single building the genetic diversity of bed bugs is limited. However, the NCSU scientists explain that the genetic diversity of bed bugs throughout East Coast high – the pests come from several places, from both within the USA and abroad.

Domestic and international travel is a major factor in the increase of bed bug infestations. Industrial poultry production is another – bed bugs feed on chickens. Household furniture and items are also partly responsible for the explosion in the number of reported infestations in the USA.

Heat treatment and insecticides are currently used to deal with infestations. Insecticides which humans have easy access to have not usually been tested on bed bugs, the researchers stressed.

With heat treatment you heat the whole home – furniture and belongings can be packed in boxes and heated at a high temperature for about sixty minutes. These options are expensive and not suitable for long-term infestations. President of ASTMH, Peter J. Hotez, MD, PhD, said:

“Just as with other global diseases once thought under control and then neglected, bed bugs have shown the ability to resurge in great numbers once our vigilance wanes.To stay one step ahead of bed bugs and other parasitic organisms, we need to sustain investment in research for new tools.”

Written by Christian Nordqvist