Penn Study Shows Bed Bugs Can Transmit Parasite that Causes Chagas Disease
The bed bug may be just as dangerous as its sinister cousin, the triatomine, or “kissing” bug. A new study from Penn Medicine researchers in the Center for Clinical Epidemiology and Biostatistics demonstrated that bed bugs, like the triatomines, can transmit Trypanosoma cruzi, the parasite that causes Chagas disease, one of the most prevalent and deadly diseases in the Americas.
The role of the bloodsucking triatomine bugs as vectors of Chagas disease—which affects 6 to 8 million worldwide, mostly in Latin America, and kills about 50,000 a year—has long been recognized. The insects infect people not through their bite but feces, which they deposit on their sleeping host, often around the face, after feeding. Bed bugs, on the other hand, are usually considered disease-free nuisances whose victims are left with only itchy welts from bites and sleepless nights.
In a study published online this week in the American Journal of Tropical Medicine and Hygiene, senior author Michael Z. Levy, PhD, assistant professor in the department of Biostatistics and Epidemiology at the University of Pennsylvania’s Perelman School of Medicine, and researchers at the Universidad Peruana Cayetano Heredia in Peru conducted a series of laboratory experiments that demonstrated bi-directional transmission of T. cruzi between mice and bed bugs.
In the first experiment run at the Zoonotic Disease Research Center in Arequipa, Peru, the researchers exposed 10 mice infected with the parasite to 20 uninfected bed bugs every three days for a month. Of about 2,000 bed bugs used in the experiment, the majority acquired T. cruzi after feeding on the mice. In a separate experiment to test transmission from bug to mouse, they found that 9 out of 12 (75 percent) uninfected mice acquired the parasite after each one lived for 30 days with 20 infected bed bugs.
In a third experiment, investigators succeeded in infecting mice by placing feces of infected bed bugs on the animal’s skin that had either been inflamed by bed bug bites, or scraped with a needle. Four out of 10 mice (40 percent) acquired the parasite by this manner; 1 out of 5 (20 percent) were infected when the skin was broken by the insect’s bites only. A final experiment performed at the Penn bed bug lab in Philadelphia demonstrated that bed bugs, like triatomines, defecate when they feed.
“We’ve shown that the bed bug can acquire and transmit the parasite. Our next step is to determine whether they are, or will become, an important player in the epidemiology of Chagas disease,” Levy said. “There are some reasons to worry—bed bugs have more frequent contact with people than kissing bugs, and there are more of them in infested houses, giving them ample opportunity to transmit the parasite. But perhaps there is something important we don’t yet understand about them that mitigates the threat.”
T. cruzi is also especially at home in the guts of bed bugs. “I’ve never seen so many parasites in an insect,” said Renzo Salazar, a biologist at the Universidad Peruana Cayetano Heredia and co-author on the study. “I expected a scenario with very low infection, but we found many parasites—they really replicate well in the gut of the bed bugs.”
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