April 14 is World Chagas Disease Day. Since its discovery in 1909 by Brazilian researcher Carlos Ribeiro Justiniano Chagas, a Chagas disease epidemic has spread from the rural areas of Latin America to the United States. When untreated, patients are at risk for disorders including arrythmias, dilated cardiomyopathy, or heart failure, so raising awareness among healthcare providers is a priority.
Bernardo Lombo, MD, is an assistant professor of clinical medicine at the Yale School of Medicine and an expert in Chagas disease at Yale. Erica J. Rayack, is a joint-degree MSN/MPH student studying epidemiology of microbial diseases and family medicine at the Yale School of Public Health and the Yale School of Nursing. Rayack created an anonymous provider survey to assess knowledge of Chagas disease. We spoke with them about access to Chagas disease screening and medical services.
When did you learn about Chagas disease?
Erica J. Rayack: I first learned about Chagas disease from a Costa Rican physician who taught much of my study abroad program. Later, I learned more about the global burden of this disease while doing independent research for a global health class at the Yale School of Public Health. I was struck by just how neglected the disease is, especially in the United States where it’s estimated that just under 300,000 people have it, and anywhere from about 20 to 100 infants in the U.S. are born with the infection each year.
How does the infection spread?
EJR: The infection spreads through an insect vector. It’s been thought that most infections are caused by the insect biting a person, taking a blood meal, and then defecating parasite-infested feces near the bite area. However, there are now regions of the world where oral ingestion of the protozoan parasites is seen as the primary source of infection. Rather than a bite being to blame, oral ingestion would be due to something like a fresh fruit juice contaminated with the infected bug or bug feces. This has been hypothesized as a main route of autochthonous infection in the US as well, but, as far as I understand, that is an area that requires more research.
EJR: The number of congenitally-infected infants born in the U.S. each year is similar to that of phenylketonuria, which is typically diagnosed through newborn screening. The importance of screening a birthing parent or a patient contemplating pregnancy is highlighted both by the reduced risk of congenital transmission in patients treated prior to pregnancy, as well as the greater than 90% cure rate in infants treated within the first year of life. This high cure rate presents health care providers with a critical opportunity to prevent spread of Chagas disease from one generation to the next.
How might global warming or other factors contribute to the risk of infection?
EJR: Climate change is a factor that we think about with any insect vector. Triatomines can already be found in much of Latin America and almost 30 states in the U.S. Habitat loss changes where insects move in relation to humans, biting rates can change, reservoir species can become more accessible, or even an insect vector’s ability to transmit pathogens can change. We have a lot of research on this for vectors like mosquitos, which, of course, cause many more diseases than triatomine bugs. There are researchers in the U.S. tackling these kinds of questions in regard to Chagas disease and triatomine bugs, but it's an area that can use more attention as our climate continues to be altered by human activities. Whether the vector will pop up in new regions of the U.S. and belong to a species or subspecies capable of carrying and spreading the parasite remains to be seen, but it is certainly a concern of many Chagas researchers.
Having lived in a highly endemic region is a major risk factor. Countries with high prevalence of Chagas disease include Bolivia, Venezuela, Brazil, and Argentina, but the vectors and the disease itself extend throughout the Americas, including the Southwest United States. The risk of acquiring Chagas disease is often associated with living in rural parts of Latin America, though there are many exceptions to this rule. In the United States, even in the southwest, we are far less likely to come in contact with a parasite-carrying triatomine bug than in other areas of the Americas. That said populations are not static. People have never been known for always staying in one place. People emigrate and travel, and someone may move from a country like Bolivia, where screening programs for Chagas disease are relatively robust, to a country like the US, where almost no health care providers were taught to even consider screening their at-risk patients. Other providers may not perform a test until symptomatic Chagas disease has already developed. Thankfully, several groups in the U.S. are working to change this situation of continued neglect, such as the Strong Hearts program in East Boston, LASOCHA [Latin American Society of Chagas] out of the D.C. area, the Center of Excellence for Chagas Disease in Los Angeles, and public health professionals and clinicians at Texas A&M University. My hope is that our various specialties, schools, and clinical programs at Yale come together and focus more heavily on this health equity issue.
One of the best resources for health care providers, students, and researchers hoping to learn more are the Chagas disease sessions put out by UT Health San Antonio Project ECHO (Extension for Community Healthcare Outcomes). All past sessions are available on their website and CMEs are available for those who register and attend the sessions live.
Chagas disease prevention and research
Describe the complexities around Chagas disease testing?
EJR: One of the major complexities with encouraging more frequent testing is that in so much of the U.S. we don’t have strong programs to support patients after diagnosis and during treatment. Furthermore, we need more research and evidence to bolster or challenge current screening recommendations. For instance, one major recommendation is to screen patients who have lived a significant amount of time in an endemic country, but at what age might that screening have little to no benefit? Published recommendations do not specify for now.
Due to low specificity, two different assays should be used for diagnostic testing, following Pan American Health Organization and Centers for Disease Control and Prevention (CDC) guidelines. In the U.S. there are three ELISAs and one rapid immunochromatographic assay, all of varying accessibility to providers. Two positives are required for confirmed diagnosis and in the case of discordance, a third distinct test would need to be performed. Commercial labs may only carry one assay type, so, often, confirmatory testing must be done through the CDC.
What are the current recommendations for high-risk populations?
EJR: In 2022 Recommendations for Screening and Diagnosis of Chagas Disease in the United States was published in The Journal of Infectious Diseases. The authors are experts on Chagas disease in the U.S., including public health professionals, clinicians, and researchers. They published four major recommendations which they ranked by importance:
- Born in or lived >6 months in an endemic country (Mexico, Central or South America).
- Having a family member with Chagas disease.
- Lived in housing made of natural materials (mud, adobe, thatch, palm leaves) in Mexico, Central or South America,
- Being bitten by kissing bugs or finding kissing bugs in the home.
They go beyond this in their paper, including other valuable recommendations in their Table 2., such as what to do after an electrocardiogram abnormality is found in an at-risk patient.
Can you describe future areas of research?
EJR: Research on Chagas disease at Yale should be paired with more robust asymptomatic screening, whether that be for all higher risk patients, or targeted toward at-risk pregnant patients. The Yale New Haven Health System, Yale School of Public Health, Yale School of Medicine, Yale School of Nursing, and physician associate program provide fertile ground for developing a robust program, both for research and patient care. Ideally there would be community outreach, patient support programs, and interdisciplinary networks of healthcare professionals. As with any screening program, one of the most important things is to have an appropriate plan for screened patients who test positive, and for that we need collaboration between all relevant specialties.
Serological diagnosis in patients with suspected Chagas disease
Bernardo Lombo: Cardiologists should order T. cruzy serologic testing for patients with the epidemiological risk factors and:
- The presence on ECG of right ventricular branch block, left anterior fascicular block, first degree AV block, premature ventricular contractions, ventricular tachycardia, atrial fibrillation.
- Patients with congestive heart failure /reduced left ventricular function
- Presence of regional wall motion abnormalities on echocardiogram especially apical or basal inferolateral aneurysms