Carlos Chagas

Carlos Justiniano Ribeiro Chagas was a Brazilian doctor and researcher who specialized in sanitation and microbiology. He is most famous for identifying the protozoal infection now known as Chagas disease, or American trypanosomiasis, and he also discovered the fungus that causes pneumocystis pneumonia. In 1909, while based at the Oswaldo Cruz Institute in Rio de Janeiro, he described both pathogens. He named the parasite *Trypanosoma cruzi* after his colleague and friend Oswaldo Cruz.

Chagas’s work stands out in medical history because he fully characterized a previously unknown infectious disease, including its pathogen, insect vector (the triatomine bug), animal hosts, symptoms, and how it spreads. He was also the first person to find and illustrate the parasitic fungus *Pneumocystis*, which later became notorious for causing pneumonia in AIDS patients.

Chagas was born on 9 July 1879, the eldest of four children. His father, a coffee farmer, died when Chagas was four. At age seven, his mother sent him to a Jesuit boarding school in São Paulo. In 1888, political unrest following Emperor Dom Pedro II’s abolition of slavery forced him to leave that school. He then attended a closer Catholic school, San Antonio, where he finished his secondary education.

He enrolled in mining engineering at Ouro Preto but contracted beriberi in 1895, which prevented him from continuing. While recovering in Oliveira, his uncle, a physician named Carlos Ribeiro de Castro, convinced him to study medicine. In 1896, Chagas entered the Medical School of Rio de Janeiro. For his dissertation, his mentor Francisco Fajardo suggested he research malaria, since British medical officer Ronald Ross had recently discovered how it was transmitted. Fajardo introduced Chagas to Oswaldo Cruz, founder of the Manguinhos Institute, who became his guide. This began a lasting friendship and Chagas’s lifelong association with Cruz’s institute. He graduated in 1902 with a dissertation on malaria and earned his doctorate the next year with a thesis on the hematological aspects of malaria.

After briefly working as a doctor in rural areas, Chagas took a position fighting malaria. In 1905, he worked for the Docas de Santos company at the port of Santos, São Paulo, tasked with controlling a malaria epidemic among workers. His successful prevention efforts allowed the port’s construction to finish. He innovated by using pyrethrum insecticide in homes, with striking results. His published work on this method became the global basis for malaria prevention and was adopted by a newly created Brazilian Ministry of Health service.

In 1906, Chagas returned to Rio de Janeiro and joined the Oswaldo Cruz Institute, where he spent the rest of his career. In 1907, a malaria outbreak among railroad workers in the Minas Gerais hinterland threatened construction of a new railway from Rio to Belém in the Amazon. The Brazilian government asked Cruz for help, and Cruz sent Chagas and an assistant, Belisario Penna, to investigate. They camped in Lassance, a small town near the São Francisco River, for two years. Chagas contained the infection within a year.

During his malaria work in Lassance, Chagas noticed that rural houses were heavily infested with a large blood-sucking insect of the genus *Triatoma*, known locally as the *barbeiro* (barber) because it bit people’s faces at night. In his own account, he described first encountering the bug during a trip to Pirapora, when an engineer showed it to him and his assistant. Intrigued by its blood-feeding habits and prevalence in homes, Chagas suspected it might transmit a parasite to humans or other vertebrates. He found flagellate protozoans in the insects’ intestines—a new species of *Trypanosoma*—and proved experimentally that infected bugs could transmit it to marmoset monkeys. He named the parasite *Trypanosoma cruzi* in honor of Oswaldo Cruz, later briefly calling it *Schizotrypanum cruzi* before settling on the original name.

His suspicion that the parasite could infect humans proved correct. He soon found it in the blood of a cat. Then, on 14 April 1909, he took blood samples from a two-year-old girl named Berenice Soares de Moura, who lived in the same hut as the cat, and discovered the parasite in her blood for the first time.