A dangerous, sometimes deadly, infection spread by kissing bugs is regularly spreading within America. In a recent paper, researchers are claiming that Chagas disease is endemic to parts of the southern U.S. and is probably here to stay.
Scientists in Florida, Texas, and California made the case in a paper published last month in the journal Emerging Infectious Diseases. Citing evidence from infected humans, animals, and kissing bugs, they argue that Chagas has established a persistent presence in the country, albeit at low levels. Correctly recognizing that Chagas is endemic, they say, will allow us to better combat the infectious disease, which can cause chronic heart problems if left untreated.
The kissing bug disease
Chagas is caused by the parasite Trypanosoma cruzi, and the infection is spread by various species of kissing bugs, or triatomines. As their nickname implies, kissing bugs feed by sucking blood from around a host’s mouth (or sometimes eyes). The bugs usually infect people via the poop they leave behind near a bite wound.
People infected with the parasite can first experience an acute phase of flu-like illness, after which the infection enters a chronic phase if left untreated. Most people avoid any symptoms in either phase, but up to a third of people with chronic Chagas disease will eventually experience serious health problems, such as an enlarged heart and colon. People can also die from heart failure or sudden cardiac arrest as a result of the infection. It can take years and even decades for these chronic symptoms to appear.
About 8 million people worldwide are thought to have Chagas, including 280,000 in the United States. Most of these U.S. cases were caught elsewhere, particularly in parts of Central and South America where T. cruzi is locally circulating. But the researchers present evidence that the parasite has probably made a cozy home within the southern U.S. as well.
Why Chagas should be seen as endemic
For starters, there have likely been locally acquired (autochthonous) human cases of Chagas documented in at least eight states, including Texas, California, and Florida. These cases are typically found in people with no relevant travel history or other risk factor for having caught the parasite outside of the area.
The researchers additionally note that southern U.S. states are known to have several kissing bug species that can theoretically carry and transmit the T. cruzi parasite, including species that will regularly invade human dwellings.
And studies have detected the parasite circulating among local kissing bug populations. Just last July, for example, researchers found that a third of kissing bugs collected in Florida carried the parasite. The parasite has also been commonly found in local wildlife, captive animals, and pets (dogs in particular), providing a reservoir for it to survive in the environment.
All of these bits of data together point to a single conclusion. “T. cruzi and the ecologic conditions that sustain its transmission cycles are naturally occurring throughout the southern half of the United States,” the researchers wrote.
A low-level but persistent threat
The one silver lining is that Chagas is likely hypoendemic to the southern U.S., the researchers say, meaning it’s only present in low levels. But as things stand now, we’re largely fighting blind against it.
Chagas disease in people is not a nationally notifiable condition, so doctors in most places aren’t obligated to report cases to their health departments, the researchers point out. It is notifiable in some of the states where local cases have been found, but not all (in California, only two counties require notice).
While Chagas might not be as huge an issue in the U.S. as it is in other parts of the Americas, classifying it as endemic will allow scientists to better track its distribution and range, the researchers say. Improved awareness of the disease will also make it easier for infected people to get the timely care they need before their infection turns into something more serious and potentially life-threatening.
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