Carlos Chagas - The Discovery of Chagas Disease

The Discovery of Chagas Disease

In 1906, Chagas returned to Rio de Janeiro and joined the Oswaldo Cruz Institute, where he remained working for the rest of his life. In 1909, he was sent by the Institute to the small city of Lassance, near the São Francisco River, to combat a malaria outbreak among the workers of a new railroad to the city of Belém in the Amazon. He stayed there for the next two years and soon was able to observe the peculiar infestation of the rural houses with a large hematophagous insect of the genus Triatoma, a kind of "assassin bug" or "kissing" bug (barbeiro or "barber" in Portuguese, so called because it sucked the blood at night by biting the faces of its victims). He discovered that the intestines of these insects harbored flagellate protozoa, a new species of the Trypanosoma genera, and was able to prove experimentally that it could be transmitted to marmoset monkeys which were bitten by the infected bug. Chagas named this new parasite Trypanosoma cruzi in honor of Oswaldo Cruz and later that year as Schizotrypanum cruzi and then once again as Trypanosoma cruzi.)

Chagas suspected that the parasite could cause human disease, due to the prevalence of the insect vector in human households and its habit of biting people, so he took blood samples and, on April 23, 1909, discovered for the first time the same Trypanosoma parasite in the blood of a three year-old girl. He also observed parasitic inclusions in the brain and myocardium which would explain some of the clinical manifestations in diseased people and closed the proposed life cycle of the parasite by suggesting that the armadillo could be its natural reservoir. To complete his work on the pathology of the new disease, Chagas described 27 cases of the acute form of the disease and performed more than 100 autopsies on patients who exhibited the chronic form.

His description of the new disease was to become a classic in medicine and brought him domestic and international distinction. He was elected to the National Academy of Medicine and received the prestigious Schaudinn Prize for the best work in protozoology and tropical medicine, on June 22, 1912. The contenders were luminaries such as Paul Ehrlich (1854–1915), Emile Roux (1853–1933), Ilya Mechnikov (1845–1916), Charles Laveran (1845–1922), Charles Nicolle (1866–1936) and Sir William Boog Leishman (1865–1926), several of them who had already received or would receive the Nobel Prize for Medicine. Chagas was twice nominated for the Nobel Prize, in 1913 and 1921, but never received the award.

Chagas was also the first to discover the parasitic fungal genus Pneumocystis in the lungs of his Trypanosome-experimentally infected animals. At the time he did not recognize it as a separate organism and therefore he described his genus Schizotrypanum to accommodate both life-cycles that he illustrated beautifully. But, his discovery led others to further investigate and describe Pneumocystis as a distinct genus, which is now known to be a fungus. Chagas, followed the literature closely and quickly confirmed the distinction, whereupon he again adopted the name Trypanosoma cruzi that he had originally coined. Pneumocystis is now linked to another disease, PCP or Pneumocystis pneumonia caused by one species (P. jirovecii) but the original Pneumocystis species seen by Chagas in Guinea pigs has not yet been named as a separate species.