Chagas: An Emerging Infectious Disease Threat In U.S.
October 1, 2015 | By: Judy Stone
Chagas, a parasitic disease, is the latest invisible killer infection to be recognized as a growing threat here. The infection is transmitted by the Triatomine bug, known as the “kissing” bug. The bugs infect people through bites—often near the eyes or mouth—or when their infected feces are accidentally rubbed into eyes or mucous membranes. Some transmission occurs from mother to child during pregnancy. Occasionally, transmission is through contaminated food or drink.
Most people in the U.S. with Chagas disease probably became infected as children, living in Latin America. The infection often has few symptoms early on, but after several decades, strikes fatally, often with sudden death from heart disease. I suspect that, similar to Lyme disease, the magnitude of disease and deaths from the protozoan parasite, Trypanosoma cruzi, which causes Chagas disease, is unrecognized in the U.S.
In Latin America, however, up to 12 million people might be infected, with a third going on to develop life-threatening heart complications. Chagas is a major cause of congestive heart failure and cardiac deaths, with an estimated 11,000 people dying annually, according to the WHO.
There are an estimated 300,167 people with Trypanosoma cruzi infection the U.S., including 40,000 pregnant women in North America. There are 30,000-45,000 cardiomyopathy cases and 63-315 congenital infections each year. Most of the people come from Mexico, El Salvador, Guatemala, Honduras, or Argentina; Bolivia has the highest rate of Chagas in the world.
But in the U.S., we don’t often think of Chagas. Even as an infectious disease physician, I’ve never treated anyone with it, and it is not on my radar. So when a physician sees a patient who may have come to the U.S. as a child, and now has diabetes and hypertension, he or she is likely to attribute the heart disease to that and not look for infection. In fact, though, there are large pockets of undiagnosed disease. For example, a survey in Los Angeles of patients with a new diagnosis of cardiomyopathy who had lived in Latin America for at least a year, found 19% had Chagas disease, and they had a worse prognosis than those without the infection.
There are other reasons Chagas is overlooked. One is that Chagas is not a reportable disease except in four states, and Texas only began reporting in 2010. Most cases here have been detected by screening of blood donations, which has found about 1 in every 27,500 donors to be infected, according to CDC. However, a 2014 survey showed “one in every 6,500 blood donors tested positive for exposure to the parasite that causes Chagas disease.” A map of positive donations is here. While the triatome bugs are most common in the southern half of the U.S., they are actually quite widespread, as shown here.
Much bigger barriers to diagnosis are social and cultural. Many patients lack health insurance. Others are undocumented immigrants fearing deportation. Health literacy and language barriers are huge. There is a stigma associated with the diagnosis, as there is for many patients with TB, as Chagas is associated with poverty and poor living conditions. As Daisy Hernández noted in her excellent story in the Atlantic, “it’s hard, if not impossible, for moms with Chagas and no health insurance to see the doctors who would connect them to the CDC” and “patients don’t necessarily have savings in case they have adverse reactions to the medication and can’t work.”
There are pockets of Chagas in the states, including Los Angeles, the Washington metropolitan area, and the Texas border, where there are large immigrant communities from endemic areas. But I suspect that with climate change, we’ll see more Chagas in the southwest U.S., as more triatomine bugs are found further north. One recent study found more than 60% of the collected bugs carried the Trypanosome parasite, up from 40-50% in two similar studies. There are also now seven reports of Chagas infection that are clearly autochthonous, or locally acquired. University of Pennsylvania researcher Michael Levy has shown that bedbugs might be capable of transmitting Chagas, but no one has shown that they actually do. Entomologist and Wired author Gwen Pearson nicely explains why bedbugs are an unlikely vector and notes that you “far more likely to be injured by misusing pesticides to try to exterminate” them.
There’s more bad news. Treatment for Chagas is effective if given early in infection, although with significant side effects. There is no effective treatment for late stages of gastrointestinal or cardiac disease. A newly released study showed that benznidazole was no more effective than placebo in reducing cardiac complications, even though it reduced levels of parasites in the blood.
The two drugs available to treat Chagas, benznidazole and nifurtimox, are not yet FDA approved and are only available through the CDC under investigational protocols. Both carry significant side effects. Treatment of children with early Chagas is generally effective but, as with many drugs, treatment is hampered by lack of data on pediatric dosing and limited formulations. There is little research funding for new drug development, with less than US $1 million (0.04% of R&D funding dedicated to neglected diseases) focused on new drugs for Chagas disease, according to the Drugs for Neglected Diseases Initiative (DNDi).
Where do we go from here? The most immediate and cost-effective proposals are to increase surveillance for disease and screening of high-risk populations. Since the most effective treatment is given early in the course of infection, screening of pregnant women and children is a priority, as is education for these women and Ob-Gyn physicians.
While there is no effective treatment for advanced disease, efforts are underway to develop a vaccine against Chagas. The National School of Tropical Medicine at Baylor College of Medicine just received a boost from a $2.6 million grant from the Carlos Slim Foundation for their initiative.
Chagas, like sickle cell, highlights disparities in access to screening and early treatment for serious illnesses disproportionately affecting the poor and people of color. While a moral and ethical issue, the choices made to gut public health programs for “cost saving” will also be unnecessarily costly in the end.
About: Judy Stone
I cover infectious diseases, medicine, drug development, and ethics.
I am an Infectious Disease specialist, experienced in conducting clinical research and the author of Conducting Clinical Research, the essential guide to the topic. I survived 25 years in solo practice in rural Cumberland, Maryland, and now work part time as an Infectious Diseases locum tenens physician. I especially love writing about ethical issues, and tilting at windmills as I advocate for social justice. As part of my overall desire to save the world when I grow up, I have become particularly interested in neglected tropical diseases. In my next life, I would love to teach overseas. When not slaving over hot patients, I can be found playing with photography, friends’ dogs, or in my garden. Follow on Twitter @drjudystone