The bed bugs are coming and they are tougher than ever before

Written by Thomas Hesselberg

Tuesday, 24 February 2009

The bed bug (Cimex lectularius) sucking blood from a human. Wikimedia Commons courtesy of the U.S. Department of Health and Human Services.

A new study by biologist from the University of Kentucky shows that the bloodsucking bed bugs are increasing in numbers. The reason for this became clear, when the scientists subjected the bed bugs to a number of insecticides and observed their behaviour. The insects did not avoid the insecticides and when were able to cross insecticide barriers when exposed to sublethal doses.

Bed bugs are small night-active insects in the family Cimicidae (order hemiptera). Different species are found in both temperate and tropical regions, where they feed by sucking blood from humans and other warm-blooded hosts. Bed bugs are flattened, brown and have a length of 4-5 mm. They are attracted to body heat and CO₂, and typically feed every 5-10 days, but they can survive for almost a year without feeding.

The bites themselves are not painful to humans, but sometime after the bite the bite site swells and starts to itch. Infested beds often results in multiple bites every night and can cause insomnia so treatment and pest control is necessary. Bed bugs, however, are not known to transmit any diseases.

Scientists from the University of Kentucky studied the behavioural response of bed bugs to two insecticides (deltamethrin and chlorfenapyr) in the laboratory. They maintained a colony of bed bugs collected in different American cities by feeding them heated rabbit blood. The insects were then observed and video filmed when given a choice between two shelters, one of which was impregnated with an insecticide. In a separate set of experiments the scientists investigated whether the bed bugs would cross a barrier of insecticide soaked filter paper to reach food.

The results showed that chlorfenapyr was not avoided by the bed bugs. Some groups of bed bugs avoided deltamethrin whereas others apparently had developed resistance towards it. All groups of bed bugs were able to cross insecticide barriers to reach food.

The scientists conclude that current treatment of a bed bug infection requires large amount of insecticide to ensure lethal doses. However, with more effective insecticides and a better knowledge of bed bug behaviour can ensure a more effective treatment.

Reference
Romero, A., Potter, M. F. And Haynes, K. (2009) Behavioral responses of the bed bug to insecticide residues. Journal of Medical Entomology 46: 51-57.

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