Serological response to nifurtimox in adult patients with chronic Chagas disease: An observational comparative study in Argentina

Author summary Nifurtimox has been a treatment for Chagas disease since the 1970s, is a World Health Organization Essential Medicine, and was recently approved to treat pediatric patients in the USA. Chagas disease is typically transmitted to humans via insect bites and is endemic in parts of Latin America. Symptoms may be mild or absent in the early acute phase of disease and about two-thirds of individuals remain largely asymptomatic in the subsequent chronic phase. However, some chronic patients experience severe cardiac or gastrointestinal effects up to 30 years after infection. Chronic Chagas disease is treatable, but positive serology can persist long after the parasite has been cleared. Studies of the effectiveness of nifurtimox in the chronic phase of the disease have historically been limited by small size or short follow-up duration. From 3,633 patients with Chagas disease identified during review of hospital records in Argentina, we analyzed data retrospectively from 1,497 adults diagnosed with chronic Chagas disease over a 14-year period (1967-1980), looking for negative seroconversion among individuals who received nifurtimox or were untreated. The study had limitations that impact interpretation of the findings: treatment regimens and the amount of time patients were followed both varied, and many untreated patients unexpectedly underwent spontaneous negative seroconversion. However, patients treated with nifurtimox were at least twice as likely to be seronegative as untreated patients, providing supporting evidence for the effectiveness of nifurtimox in adults with chronic Chagas disease.