Bed Bugs Dying After Merck Drug Suggests Possible Weapon

Bed bugs died after feeding on people treated withMerck & Co.’s (MRK) Stromectol, a treatment typically used against parasitic worms, in the first study to investigate the drug’s potential to control the blood-suckers.

Three out of five bed bugs died after blood meals from people who had taken Stromectol, also called ivermectin, three hours earlier, according to research presented at a scientific meeting in Atlanta yesterday. The pill, along with conventional measures such as pesticides, may improve chances of eliminating the pest, said John Sheele, an emergency physician at Eastern Virginia Medical School in Norfolk, who led the study.

Stromectol is used to treat diseases caused by worm parasites such as river blindness, one of the leading causes of preventable blindness, and elephantiasis, or lymphatic filariasis, which causes certain parts of the body to become enlarged. Sheele’s research suggests its pesticidal properties may also fight bed-beg incursions, experienced by more than 400,000 New York City residents in 2009.

“Ivermectin is effective against a broad range of insects — body lice, head lice, scabies,” Sheele said in an interview. “What I’d like to be able to do is a real-world experiment where we find people who have bed bugs, treat them with the regimen and see does it get rid of their infestation.”

Bed bugs are small, flat insects that feed solely on the blood of people and animals while they sleep. The reddish-brown, wingless parasites are found across the globe from North and South America, to Africa, Asia and Europe. While they aren’t known to spread disease, bed-bug bites can cause itchy welts, excessive scratching of which can lead to skin infections, according to the Centers for Disease Control and Prevention.

Blood Meals

Sheele tested ivermectin, sold as Mectizan outside the U.S., on himself and three colleagues over five bed-bug blood meals. They allowed three adult and three juvenile bed bugs to feed on them before taking the drug. Then, using the same combinations of different insects, the test subjects allowed feeds 3, 8, 22 and 54 hours after consuming a standard dose, equivalent to 200 micro grams per kilogram of bodyweight.

Within three hours of feeding on ivermectin-laced blood, the apple-seed-sized critters were falling sick and dying, Sheele said. Ivermectin was most lethal for both juvenile and adult bed bugs on the first day of treatment, though it killed 42 percent of adults 54 hours after the drug was taken. Ivermectin also hampered the ability of beg-bug nymphs to shed their outer exoskeleton — a key step in their development.

The research, funded by Eastern Virginia Medical School’s department of emergency medicine, was presented at the American Society of Tropical Medicine and Hygiene’s annual meeting.