It was previously thought that Chagas disease, which kills an estimated 50,000 people per year, was exclusively carried by an insect called the kissing bug. But new research shows that bedbugs can also spread the disease, at least among mice.
University of Pennsylvania epidemiologist Michael Levy says he’s worried that bedbugs could distribute the parasitic disease among people, although there is no proof yet that this is happening.
Chagas disease is caused by a parasitic protozoan called Trypanosoma cruzi that slowly attacks internal organs like the heart. At first, it has very few outward signs. Then, about 20 years after infection, some 20 percent of infected people develop very serious problems, including arrhythmias and even sudden death from cardiac arrest, Levy tells Newsweek.
Due to this time lag and lack of recognition, Chagas disease has become a “silent epidemic”—it’s the most deadly parasite in the Americas, but the public doesn’t know anything about it, Levy says.
The parasite is spread by kissing (or “assassin”) bugs, which generally feed at night and go for uncovered areas like the face, often around the eyes or lips. These insects don’t directly spread the disease through their bite, but rather through feces; the protozoan can be transmitted when their waste is spread into wounds via scratching, or by entering the body through the eyes or mouth, Levy says.
Luckily, kissing bugs cannot generally get to humans at night if they live in well-made buildings. That’s one reason why Chagas disease transmission isn’t a significant problem in the U.S.—the few cases seen in the States are mostly brought in by travelers returning from Latin America.
In the past few years, however, bedbug populations have skyrocketed in the U.S. If these insects could spread the disease, and, says Levy, “it would be a disaster.… If Chagas starts to spread, we wouldn't know it, due to the slow nature of the disease.”
In a study published this week in the American Journal of Tropical Medicine and Hygiene, researchers showed that bedbugs can become infected after feeding on diseased mice. They also found in another experiment that protozoa-carrying bedbugs can pass on the parasite to mice.
Since the protozoa infects many mammals, including mice and humans, there’s no reason to think bedbugs couldn’t spread the disease among people too, Levy says, although he concedes there may be some as-yet-unknown reason why bedbugs couldn’t transmit the disease.
“Any time you have an infectious disease and identify a new route of infection, that's something to be concerned about,” says Rick Tarleton, a Chagas disease expert at the University of Georgia who wasn’t involved in the study.
Levy and colleagues demonstrated that many bedbugs do defecate shortly after feeding, increasing the chances that this insect could transmit the disease to humans via open wounds or another route. And bedbugs have an even closer relationship with humans than kissing bugs; certain infestations involve scores of insects feeding on humans every night, Levy says.
“Just for example let’s say you have bedbugs in a bed, and an infant in that bed with a pacifier, which comes into contact with [insect feces] and goes into the mouth,” Tarleton says. “That’s a potential transmission.”
Officials have made strides at reducing Chagas disease in countries like Peru, by going door-to-door and spraying insecticides for kissing bugs. But these insects are much easier to kill than bedbugs, which may be resistant to various chemicals and harder to find, Levy says. If bedbugs, which are spreading throughout South America, pick up Chagas, it could set back all of this progress by decades, he adds.
“I think the [study] is concerning, but it's not an over-the-top disaster,” Tarleton says. Not yet, anyway.