Charles Darwin, Chagas’ disease, and the killer kissing bugs of California

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It is possible, although very unusual, to get Chagas’ disease in the United States. The medical journal Open Forum Infectious Diseases recently reported a case of Chagas’ disease acquired in California. A healthy 19-year-old student from the greater Los Angeles area donated blood, and tested positive for Chagas’ disease. (Blood donations in the United States are routinely screened for Chagas’ disease, as it is estimated that 300,000 Latin American immigrants in the United States have been infected with Trypanosoma cruzi.) He had never traveled to Latin America; his infection probably came from a kissing bug bite in his sleep during one of several camping trips in southern California. Tests showed no evidence of heart damage. He had a good response to four months of treatment with the anti-parasitic drug nifurtimox, although this drug gave him temporary side effects of anxiety and depression.

Kissing bugs are found in much of the United States. However, only kissing bugs in the southwest United States are highly likely to carry Trypanosoma cruzi. Kissing bugs in California and Texas may be especially likely to spread Chagas’ disease. In one study, 28% of kissing bugs from southern California and 55% of kissing bugs from northern California were carrying Trypanosoma cruzi. In the borderlands of south Texas, 57% of kissing bugs are infected with Trypanosoma cruzi.

The major reason why the spread of Chagas’ disease is rare in the United States is housing. Housing standards in the United States are generally higher than in affected parts of Latin America, and it is rare for kissing bugs to invade homes here. However, it is possible for kissing bugs to gain entry to American houses that are dilapidated, as happened in one case of human infection in Louisiana after Hurricane Katrina.  Bed bugs, which can transmit Chagas’ disease in laboratory experiments, are common in some parts in the U.S., but there is little evidence that they are an important real-world source of infection with Chagas’ disease.

Keeping Chagas’ disease at bay

There is an urgent need for more research into the spread and treatment of Chagas’ disease in the United States. The drugs used to treat Chagas’ disease are not well tolerated, and they are not effective in patients who have already developed heart damage. At present, your risk of getting infected with Chagas’ disease in the United States is very low, especially if your house or apartment is in good shape, and you avoid camping outside in the open. However, some scientists are worried that Chagas’ disease may become more common in the future. Increasing development in areas where kissing bugs are found may bring them in contact with humans more often. As well, the kissing bugs that carry Chagas’ disease could spread northward with climate change. As Darwin might observe, it’s an evolving situation.

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