The Centers for Disease Control and Prevention considers it one of five neglected parasitic infections in need of targeted public health action. And while its transmission is still considered rare in the U.S., it seems residents of Texas may be at greater risk than scientists previously thought.
The disease is American Trypanosomiasis, more commonly known as Chagas disease. Chagas is a vector-borne disease in which the parasite is transmitted to animals and people by blood-sucking insects known as “assassin bugs” or “kissing bugs” (here’s what the bugs look like). However, the parasite isn’t transmitted through a bite, per se; as the kissing bug sucks on your blood, it may drop its feces into the wound and it’s in the feces where the parasite is found. Chagas disease is endemic in parts of Latin America, Central America and in Mexico. But the risk of Chagas isn’t entirely clear in the U.S., where some have described Chagas as an emerging disease.
Rosa A. Maldonado, an associate professor of biological sciences at the University of Texas in El Paso, was curious about the risk of Chagas in the U.S. too. She had read studies finding that a significant number of dogs in Texas had tested positive for Chagas and so it made sense that insects must be carrying the parasite as well.
“If animals are infected that means insects have to be infected around here, too,” Maldonado told me.
So, she conducted her own study, the results of which were recently published in the journal Acta Tropica. A colleague told her that there were plenty of kissing bugs at the university’s Indio Mountains Research Station in Hudspeth County out in west Texas, not far from the Mexico border. So with the help of a student, Maldonado collected 39 kissing bugs for testing. She expected that perhaps 40 percent — maybe even half — of the bugs would test positive for the Chagas-causing parasite. But in the end, 24 of the bugs — or 61.5 percent — were carrying the parasite.
“I was expecting it to be high, but not that high,” she said.
Chagas disease has an acute and chronic phase. During the acute phase, symptoms can include fever or swelling; rarely, the disease can cause severe inflammation in the heart or brain. After the acute phase, most people experience a chronic asymptomatic phase. About 20 to 30 percent of infected people will develop debilitating or life-threatening medical problems. CDC estimates that more than 300,000 people in the U.S. have the Chagas parasite, though most contracted it outside the U.S. in endemic countries and only rare cases of domestically acquired Chagas have been documented.
Maldonado’s study noted that an estimated 12 million people are infected with Chagas worldwide. A 2013 Lancet study calculated the annual global economic burden of Chagas at about $7 billion. Maldonado and her study co-authors Munir Buhaya and Steven Galvan write: “Currently, there are no vaccines against Chagas nor effective treatment for the chronic disease. Therefore, improved knowledge of the local epidemiology and ecology is needed to develop a more comprehensive assessment of the magnitude of local transmission risk that will lead to more efficient efforts to prevent transmission.”
Maldonado hypothesizes that Chagas infection is probably underestimated in the U.S., as it’s not well tracked and most doctors probably don’t think to consider Chagas as a cause of related symptoms. She noted that the U.S. Food and Drug Administration has approved diagnostic tools that blood banks can use to test for Chagas, as the disease can be transmitted by blood transfusion. While the agency doesn’t require such testing, many blood banks do test for the disease.
As for the everyday Texan, Maldonado said kissing bugs are hard to find in cities and typically live in wild areas. But if you’re worried, she said to fill in holes and cracks that a bug can use to get inside your home or keep attractive hiding places, such as piles of wood, away from your house. As for Maldonado’s future Chagas research, she plans to do more testing for Chagas in stray dogs and cats in El Paso, which would point to infected kissing bugs in the area as well.
“The good news is that if we keep screening, we can start to raise awareness,” she told me.
To request a full copy of the Acta Tropica study, see this news release from the University of Texas-El Paso.
Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.