By Ajay K. Singh, MBBS, FRCP, MBA
April 18, 2017
In managing patients with heart disease, most of us do not think about the possibility of Chagas’ disease (CD). CD is estimated to affect 5 million people worldwide and according to CDC seroprevalence estimates, affects about 300,000 people. CD accounts for nearly five times as many disability-adjusted life years lost as malaria. CD is estimated to cause approximately 7000 deaths annually.
A recent study by Sheba and colleagues of a convenience cohort of 4,755 Latin American-born residents of Los Angeles County reports that 1.24% tested positive for CD.
Bern and colleagues provide a comprehensive review of CD. The disease was discovered in 1909 and is named after the Brazilian physician Carlos Chagas; Chagas’ is also known as American trypanosomiasis.
The protozoan parasite Trypanosoma cruzi (T. cruzi) is the cause of CD. It is thought that immigrants from Latin American countries acquire the trypanosomal infection from transmission by insect vectors (carried in the gastrointestinal tract of triatomine bugs) found in impoverished rural areas of Latin America. Triatomine bugs are also known as “kissing bugs” because they bite while a person is asleep around the thin skin of the face around the eyes and mouth. T. cruzi transmission occurs when infected bug feces contaminate the bite site or intact mucous membranes, but it can also be transmitted through transfusion, via a transplanted organ, and congenitally.
CD has both an acute and chronic phase of disease. The acute phase is either asymptomatic, or associated with fever in a subset of patients with a chagoma. These chagomas contain the parasite and present with swelling and inflammation at the site of inoculation. Acute CD can rarely also present with more severe myocardial and central nervous manifestations.
The chronic phase manifests either with cardiac or digestive disease. Cardiac CD is a cardiomyopathy characterized by a chronic inflammatory process involving all chambers, conduction system damage, and a progressive dilated cardiomyopathy with congestive heart failure. Patients may also present with thromboembolism due to thrombus formation in the dilated left ventricle or aneurysm. Gastrointestinal CD disease is less common than cardiac CD and geographically distinct (mostly detected in Argentina, Bolivia, Chile, Paraguay, Southern Peru, Uruguay, and parts of Brazil rather than northern Latin America, Central America, or Mexico) and usually affects the esophagus and/or colon, resulting from damage to intramural neurons.
So what are the implications from the Sheba study? Sheba and colleagues make several recommendations. First, the prevalence of CD in the US has been underestimated and more awareness is necessary. Indeed, the US Center of Disease Control (CDC) considers CD, along with as cysticercosis, toxocariasis, toxoplasmosis and trichomoniasis, as a neglected parasitic infection. Second, earlier diagnosis and treatment of CD might significantly impact the morbidity and mortality of the disease. And, third screening strategies should be considered for individuals at high risk: Latin American immigrants from endemic areas would be at the top of the list for screening. Indeed, screening tests are available for CD. Besides these, while CD is more common among immigrants, it has been detected in native-born Americans underscoring the importance of considering CD in the differential diagnosis of a cardiomyopathy.
Dr. Ajay K. Singh is the Senior Associate Dean for Global and Continuing Education and Director, Master in Medical Sciences in Clinical Investigation (MMSCI) Program at Harvard Medical School. He is also Director, Continuing Medical Education, Department of Medicine and Renal Division at Brigham and Women’s Hospital in Boston.