Chagas disease an emerging, overlooked threat in southern US

NEW YORK - Chagas disease is an emerging public health threat across a broad swath of the southern United States and is largely underdiagnosed and treated, according to a series of studies presented today in New Orleans at the American Society of Tropical Medicine and Hygiene (ASTMH) annual meeting.

Chagas disease (American trypanosomiasis) is a tropical parasitic disease caused by the protozoan Trypanosoma cruzi transmitted by blood sucking triatomine insects, also known as "kissing" bugs for their habit of feeding on people's faces while they sleep. It can also spread through the blood supply. Since 2007, all potential blood donors in the U.S. are screened for exposure to the Chagas parasite.

In a study of Texas blood donors between 2008 and 2012, about one in 6,500 tested positive for the Chagas parasite, reported Melissa N. Garcia, epidemiologist at Baylor College of Medicine in Houston. That rate is consistent with other studies in the southern U.S., she noted, but is 50 times higher than the national rate of one in 300,000 put forth by the Centers for Disease Control and Prevention (CDC).

"We were astonished to not only find such a high rate of individuals testing positive for Chagas in their blood, but also high rates of heart disease that appear to be Chagas-related," Garcia said in a conference statement.

"About one-third of people with Chagas disease will develop heart disease from it," she noted in an interview with Reuters Health. "The heart disease is characterized by both electrical and structural abnormalities. Over the course of 10 to 30 years, patients can typically have very few signs but develop an enlarged heart, which can be fatal if not treated," Garcia said.

The Baylor team followed 17 Houston-area blood donors infected with the Chagas parasite and found that seven (41%) had undiagnosed electrocardiographic abnormalities consistent with Chagas cardiomyopathy. Six (36%) of them are suspected to have acquired Chagas in Texas. "That's really scary," Garcia said.

A separate study reported at the conference shows that most people who test positive for Chagas disease go untreated.

Dr. Jennifer Manne-Goehler, of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, reported that 1,908 Chagas cases were identified in the blood donation system from 2007-2013. But the CDC provided only 422 courses of benznidazole or nifurtimox used to treat Chagas during this period.

"This highlights an enormous treatment gap," Dr. Manne-Goehler said in a statement. "In some of the areas of the country we know there are a lot of positive blood donors, yet people still don't get care. We don't know what happens to them because there is no follow up."

Garcia and her colleagues have been working with physicians in Texas to increase awareness and diagnosis of Chagas disease.

"Traditionally, when physicians think of Chagas disease they think of someone from Latin or South America. Our study really highlights that we are starting to see cases here in the United States and in people who have never left the States -- people who don't really fit the traditional image of Chagas," she told Reuters Health.

"We've actually had a long history of Chagas in the state of Texas and in the United States," said Garcia, adding that the first case of locally acquired infection dates back to 1955.

"When we speak with cardiologists, the majority know of Chagas disease but it's not in their differential," she said. "There are very specific cardiac abnormalities associated with Chagas. Anyone that doesn't have diabetes or hypertension and is otherwise in pretty good health, but has heart problems, that's the kind of person you think of for Chagas."

While it's unclear how many triatomine bugs in the United States may carry the Chagas parasite, a pilot study conducted by the Baylor team may shed some light on the issue.

In tests on a random sample of 40 triatomine bugs found near homes in 11 central-southern Texas counties they found 73% of the insects carried the parasite and half of the positive bugs had dined on human blood in addition to animals including dogs, rabbits, and raccoons.

"The high rate of infectious bugs, combined with the high rate of feeding on humans, should be a cause of concern and should prompt physicians to consider the possibility of Chagas disease in U.S. patients with heart rhythm abnormalities and no obvious underlying conditions," Dr. Kristy Murray, associate professor of tropical medicine at Baylor, said in a statement.

References: Reuters Health
comments powered by Disqus