Though generally regarded as a nuisance or irritant pest, the common bed bug (Cimex lectularius) is known to be capable of harboring more than 40 human disease-causing pathogens. It’s the transmission back to humans that bed bugs seem not to be as good at as some of their other blood-feeding cousins. But entomologists have some evidence that bed bug feces can be a channel for disease transmission, so it’s wise to study which pathogens bed bugs can carry and just how well those pathogens can survive within them.
To that end, bed bug researchers at New Mexico State University have investigated the ability of bed bugs to carry Trypanosoma cruzi, the protozoan that causes Chagas disease, and report their findings in a new article published Friday in the Journal of Medical Entomology. In a lab experiment, the researchers found that nearly all bed bugs they fed with T. cruzi-infected blood later showed live forms of the pathogen in their guts and that T. cruzi frequently survived through its hosts’ molting.
That latter finding, known as transstadial persistence, is notable because bed bug nymphs typically molt after each blood meal, which they do five times before reaching their adult stage, says Alvaro Romero, Ph.D., assistant professor of urban entomology at NMSU and senior researcher on the study. “If T. cruzi could not persist throughout the molting process, nymphs would be less effective as vectors since they would have to feed on an infected host to reacquire the parasite in their guts after each molting. says Romero.
“Romero and colleagues Brittny Blakely and Stephen Hanson, Ph.D., sought to understand how long T. cruzi could survive within bed bugs, and they found that—in addition to the parasite surviving across nymphal stages—T. cruzi lasted as long as 97 days in adult male bed bugs fed with infected blood (whether it could last longer is unknown, as the experiment stopped after that period). The evidence might have important epidemiological implications, Romero says, in case cycles of T. cruzi infection between bed bugs and humans get established in areas endemic to Chagas disease.
Chagas disease is a vector-borne infection with symptoms ranging from mild to life-threatening, and it is spread primarily by insects in the Triatominae subfamily, a grouping of approximately 130 species found in the Americas. (They’re often known as “kissing bugs,” for their habit of feeding on sleeping humans’ faces.) The blood-feeding insects spread Chagas disease through their feces, and the infection affects as many as 8 million people in Mexico, Central America, and South America, according to the U.S. Centers for Disease Control and Prevention.
The NMSU researchers’ findings offer further evidence that bed bugs could be potentially capable of spreading Chagas disease in natural conditions. A study by the University of Pennsylvania School of Medicine published in 2015 showed bed bugs could spread the infection to mice in a lab setting, though further research is needed, Romero says, to judge whether such transmission can occur from bed bugs to humans, in a real-world setting, and to what degree.
“We also hope this work triggers interest from the Latin American research community to look in more detail at the epidemiology of Chagas, or any other disease, in their countries and better understand the potential of bed bugs to transmit the disease causal agent in natural conditions,” Romero says.