How bed bugs dodge poisons designed to control them

January 11th, 2009 - 1:08 pm ICT by ANI  

University of Massachusetts

Washington, Jan 11 (ANI): In a first of its kind study, toxicologists at the University of Massachusetts Amherst and Koreas Seoul National University have explained how bed bugs develop resistance to drugs like pyrethroid neurotoxins, especially deltamethrin, that once kept them in check.

Led by senior researcher John Clark and colleagues, the study revealed that these nocturnal bloodsuckers have evolved to trick the latest generation of chemicals used to control them since DDT was banned.

The researchers summarized that diagnostic tools to detect the relevant mutation in bed bug populations have been urgently needed for effective control and resistance management.

They specifically found that bed bugs in New York City have acquired mutations in their nerve cells, which blunt the neurotoxic effect of the pyrethroid toxins used against them.

The mutations affect sodium channels (resembling pores) in the neurons outer membrane, where electrical nerve impulses are produced.

Earlier, these nervous system poisons could effectively paralyse and kill the bugs, however, this is not the case anymore.

Resistance means mutations are acquired over time by selection with pyrethroids, so the neuronal pores no longer respond to their toxic effects.

It was found that these pores in New York City bed bugs are now as much as 264 times more resistant to deltamethrin.

This type of pyrethroid resistance is common in many pest insects and the failure of the pyrethroids to control bed bug populations across the United States and elsewhere indicates that resistance is already widespread, said Clark.

He explained that for the study, the researchers collected hard-to-control bed bugs from New York City, plus easy-to-control bed bugs from an untreated colony in Florida.

The New York population was determined to be highly resistant (264 times more resistant) to deltamethrin as compared to the Florida population by contact exposure.

Also, it was found that resistance was not due to the increased breakdown of deltamethrin (enzymatic metabolism) by the resistant bed bugs but appeared to be due to an insensitive nervous system.

Using molecular techniques, they sequenced genes related to the sodium ion channels operation in both groups and identified two mutations found only in the resistant population.

Similar mutations have been found in other pyrethroid-resistant insects and are likely the cause of the resistance in bed bugs.

The study was published in the current issue of the Journal of Medical Entomology. (ANI)

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