The discovery of Chagas disease (1908-1909): great successes and certain misunderstandings and challenges

The discovery of Chagas disease is one of the most important and resounding successes in the history of parasitic biology and human parasitic pathology. For the first time, a single researcher discovered a new parasite, its vector, experimental animals susceptible to being infected by the parasite, the acute and chronic disease caused by that parasite, and the domestic and wild cycle of the disease 1,2 . In 1907, the director of the Oswaldo Cruz Institute named Dr. Carlos Chagas the head of the malaria control program instituted for the workers who were extending the Brazilian Central Railway in the north of the State of Minas Gerais. Chagas installed himself in a train car that was both his home and his laboratory in the small town of Lassance. In 1908, while studying the blood of a small marmoset (Callithrix penicillata) that was very common in the area, he found a Trypanosoma species to which he gave the name Trypanosoma minasense. That same year, the engineer Cantarino Mota, who was involved in the railway construction, called Chagas’ attention to a type of hematophagous insect known as kissing bugs, which were living in thatched huts in the area. When Chagas inspected the huts, in the cracks of the walls, he found hundreds of these insects, which he named “Conorrhinus sanguessuga” (now called Panstrongylus megistus) (Figure 1A). Examining the hindguts of those insects, he noted the presence of numerous flagellates that he identified as “chritidias”, today known as epimastigotes (Figure 1B). At that time, he made two hypotheses: a) epimastigotes could be T. minasense in vectors; and b) the flagellates could be another human parasite. Due to the lack of adequate laboratory facilities in Lassance, Chagas sent specimens of the insects infected with flagellates to Dr. Oswaldo Cruz in Rio de Janeiro, who made the insects feed on clean marmosets (Callitrix). Three to four weeks later, by October/November 1908, the trypanosomes were found in the Callitrix blood. Cruz immediately called Chagas, who verified that the new Trypanosoma were completely different from Trypanosoma minasense due to varied morphology, with thin and thick forms and large and peripheral blepharoplasts (Figure 1C). Chagas also infected marmosets, dogs, guinea pigs, and rabbits and cultivated the parasite in agar blood medium. He named the new parasite Trypanosoma cruzi in homage to Cruz, his teacher.