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A successful vocation

Pirajá da Silva described the schistosomiasis parasite (Schistosoma mansoni) 104 years ago in Bahia


The researcher conducted detailed analyses and documented all discoveries and statements with photographsNAFTALE KATZ / CPQRR / FIOCRUZ

Physician Manuel Augusto Pirajá da Silva did not enjoy clinical work. His interests focused entirely on academic studies, an uncommon thing in 1896, when he graduated from the School of Medicine in Salvador. A native of the state of Bahia from the town of Camamu, he practiced medicine in the inner state and in Manaus (state of Amazonas), but at the first opportunity he moved to the Bahia state capital planning to only work on research into tropical diseases. It worked. In 1908, he described the parasite Schistosoma mansoni, which causes schistosomiasis and published an article about the study in Brazil and in France, in the same year, and then in England, in 1909.

“Pirajá was absolutely right to pursue his vocation for an academic life,” says Roberto Santos, a medical researcher who has been president of the Federal University of Bahia, minister of Health and governor of Bahia. “Of the academics that focused on researching tropical diseases in Bahia, his is the most original work.” The disease that Pirajá investigated is popularly known as barriga-d’água (water-belly). It mainly affects the intestines, liver and spleen and is one of the principle parasitical diseases in Brazil.

Pirajá da Silva (1873-1961) first turned to scientific research in 1902, when he was named medical clinic assistant at the School of Medicine. The head professor was Anísio Circundes, who had visited London’s School of Tropical Medicine, created by the Scotsman Patrick Manson, who established the field of tropical medicine. Circundas inspired Pirajá to become enthusiastic about this when he described research in the area.

At the time, there was as argument going on about the parasite Schistosoma haematobium, which had been discovered in 1851 by the German helminthologist Theodor Bilharz. The British, led by Manson, said that schistosomiasis might be caused by a different species of the genus Schistosoma. The Germans, led by Arthur Looss, from the Cairo School of Medicine, believed only in one species. In 1907, one of Manson’s assistants, Louios Sambon, analyzing the morphology of an egg that was different from those of S. haematobium and from a single poorly conserved worm, concluded that this was a new species. In honor of the scientist who had considered the possibility of there being other species of the same worm, Sambon called this the Schistosoma mansoni.

Pirajá was aware of the discussion. Since 1904, he had been looking unsuccessfully for S. haematobium eggs in schistosomiasis patients in Bahia. In 1908 he published in Brazil-Médico the article “Contribuição para o estudo da schistosomíase na Bahia” [Contribution to the study of schistosomiasis in Bahia]. Here, the researcher described eggs and a parasite that were different from the S. haematobium ones.

“Pirajá found eggs with a lateral spicule in the rectal mucosa and the vena cava of autopsied patients with Bahian clinical schistosomiasis,” Santos tells us. The lateral position of the eggs’ spicule (a small thorn) was different from its polar position in the S. haematobium eggs found in the bladder mucosa of Africans with the disease. “In the vena cava of the people from Bahia with schistosomiasis, he also found adult worms, both male and female, even in the copulation position.”

First, Pirajá named the new species S. americanum; subsequently, he concluded it was the same S. mansoni named by Sambon. “The difference between the work of Pirajá and Sambon is that the Brazilian described the worm in the most correct manner possible, with detailed analysis, whereas the Englishman did it based on Manson’s intuition,” says Naftale Katz, researcher emeritus at the Oswaldo Cruz Foundation, from the René Rachou Research Center in the city of Belo Horizonte.

Pirajá’s contribution as co-discoverer of S. mansoni was never publicly acknowledged by the English. The Brazilian scientist maintained correspondence with Robert Leiper, also from the English school and connected with both Manson and Looss. Leiper was always reticent about admitting, even in personal letters, the importance of the work conducted in Bahia.

Other European scientists were more generous. Proof of this is that in 1913, Pirajá da Silva was invited by the Karolinska Institute, which awards the Nobel Prizes, to nominate a candidate for the Medicine or Physiology category that year. Pirajá proposed Carlos Chagas, for his work on Trypanosoma cruzi. The official website, informs us that those who are invited to nominate candidates for the prize are people that the institute considers