As a result of the lack of systematic screening in routine health care in the United States, Chagas disease is significantly underdiagnosed, and further, a brief report published in Clinical Infectious Diseases also found that 7.4% of relatives of existing patients also have Chagas disease.
Chagas disease is caused by infection with Trypanosoma cruzi and affects over 6 million people globally, including over 300,000 in the US, where it causes a greater disease burden in disability-adjusted life-years than any other parasitic disease. Early diagnosis, in the asymptomatic phase, can greatly improve Chagas disease morbidity and mortality. This study, conducted at the Center of Excellence for Chagas Disease at the Olive View-University of California, Los Angeles Medical Center, assessed T cruzi infection prevalence in a sample of 189 relatives of 86 patients who had been previously diagnosed with Chagas disease. Blood samples were tested using a Chagatest enzyme-linked immunosorbent assay (sensitivity = 98.8%, specificity = 99.6%), and all positive results were confirmed with an immunofluorescence antibody assay or an immunoblot assay using trypomastigote excreted-secreted antigens (sensitivity and specificity = 100%) at the Centers for Disease Control and Prevention.
Of the 189 relatives tested, 86 were born in the US, 55 in El Salvador, 24 in Mexico, and the remaining participants were from other areas of Latin America. Most respondents (73.0%, n=138) had a parent with Chagas disease, and of the remaining, 28 were siblings of a patient, 16 were spouses, 5 were parents, 1 was a son-in-law, and 1 was a niece. A positive Chagas disease diagnosis was confirmed in 7.4% of respondents (n=14), with the prevalence being much higher in adults than children. Ten of the 14 individuals (71.4%) were over age 40 years. El Salvador had the most confirmed cases of Chagas disease (9 of 55, 16.4%; P =.005), and the highest prevalence by relationship type was among siblings (25%; P =.001) and parents (40%; P <.045). Only 2.9% (n=4) of the 138 respondents with a parent with Chagas disease were seropositive, and all were maternal offspring. One of the 64 respondents under age 18 years was diagnosed — a 2-month-old infant of a Salvadoran mother. This case was the only positive diagnosis in respondents born in the US.
Study investigators concluded, “Detecting T. cruzi infection early and proactively, before progression to chronic symptoms, is a crucial step to reducing the heavy burden of [Chagas disease] in the United States and elsewhere.”
Hernandez S, Forsyth CJ, Flores CA, Meymandi SK. Prevalence of Chagas disease among family members of previously diagnosed patients in Los Angeles, California [published online March 28, 2019]. Clin Infect Dis. doi: 10.1093/cid/ciz087