Chagas disease, which can cause long-term cardiac damage, is mainly found in rural Central and South America, but some experts are concerned that cases are beginning to rise in southern U.S. states. Infections have been reported in Arkansas, Arizona, Massachusetts, Tennessee and Texas, according to the CDC.
The disease is caused by the Trypanosoma cruzi parasite and is spread almost exclusively through bites from the triatomine insect, also called the "kissing bug," since it usually bites around the eyes and mouth, usually when they come out to feed at night. In rural Central and South America, the bugs are often found in the walls of homes made from mud, adobe or straw. The insect has also been found in other U.S. states but that does not necessarily mean the bugs carry the parasite, experts said.
While the disease can lead to serious complications, the vast majority of those infected will likely not show any symptoms, according to the CDC, which estimated that 300,000 people with Chagas disease live in the United States. A spokeswoman for the CDC said the agency does not have data on how many people are infected within the U.S. versus those infected before they arrive.
Dr. William Schaffner, an infectious disease expert at Vanderbilt University, said since the parasite can remain in the body for decades, it's extremely difficult to tell when a person was infected and that most people in the U.S. with the disease were likely infected before arriving in the country.
"Once the bug gets into you, it goes throughout the body and sets up quiet housekeeping ... in particular in the heart," Schaffner said. "It smolders there for many years, anywhere from 20 to 30 years."
The parasite resides in the insect's intestinal tract and can enter a human bloodstream if a person scratches a bite and the parasite enters through the scratches. The disease is not spread from person to person.
In previous decades, cardiologists almost never saw the infection, Schaffner said, but anecdotally infectious disease doctors and cardiologists are encountering the rare infection more and more.
Patients in the U.S. may have been infected years before they arrived and as they age their immune system gets weaker, and they "may develop these illnesses of cardiomyopaty or arrythmia," Schaffner said, noting the patients "had parasite silently traveling with them."
While transmission in the U.S. is rare, Schaffner said that epidemiologists are on the lookout for a rise of the Trypanosoma cruzi parasite or the triatomine insect as temperatures rise due to climate change.
"That is a smoldering concern," Schaffner said. "We're concerned that the ecology will change and as we get warmer climates ... we may see some more of certain kinds of infections and this might well be one of them."
The infection can be treated with medication, but if there is tissue damage to the heart, that has to be treated with supportive therapies, he said.