Report of First Expedition to South America. Harvard School of Tropical Medicine

Abstract

This very excellent report deals with the investigations of the first expedition sent out by the Harvard School of Tropical Medicine, to study certain forms of tropical disease occurring in South America.The report treats of the sanitary conditions of the places visited, namely, Kingston, Jamaica, Colon, Panama, Buenaventura, Guyaquil, Callao, Lima, and certain mountain towns in the interior of Peru.While at Guayaquil yellow fever was very prevalent and many cases of this disease were studied.Especial attention was paid to the study of the blood, owing to the reports of Seidlin regarding the presence of a protozoon which he has named Paraplasma flavigenum and which he regards as the cause of the disease.As a result of their investigation of the blood in yellow fever, these investigators say: "We were unable, however, to detect any bodies which suggested a parasitic nature in the blood in this disease."The larger portion of the report deals with the investigations of oroya fever and verruga peruviana and as the results of their investigations the authors have determined, apparently without question, that these conditions are distinct diseases.Verruga peruviana is due to a virus which may be transmitted to animals by direct inoculation, the nature of which is still unknown, while oroya fever is due to a parasite of the red blood corpuscle, which cannot be transmitted to animals.The parasite concerned in the etiology of this disease is of interest to protozoologists because it apparently belongs to a new genus which Strong has called Bartonella, naming the genus after Barton, who in 1905 first described the bodies within the red corpuscles.The specific organism causing oroya fever has been named Bartonella bacilliformis.Multiple infection of the red cells is common in severe infections, as many as ten of the parasites being present in one cell.Morphologically the parasites occur in the form of minute rods resembling a bacillus, measuring from 1 to 2 microns in length and rounded or oval forms, measuring from 0.3 to 1 micron in diameter.Both rods and rounded forms contain, in stained preparations, granules which may be interpreted as chromatin.The investigators were unable to infect either monkeys or rabbits with this parasite.While unable to find any parasite in the cases of verruga peruviana studied, the authors were able to produce very typical lesions in both monkeys and rabbits, thus demonstrating the distinct nature of the two diseases.They were unable to definitely decide whether the virus of verruga is filterable, but believe that ultimately it will be shown to be so.As regards the transmission of the two diseases the authors were unable to determine in what manner this occurred but lean to the opinion that some arthropod is concerned.Uta, a disease of the skin, occurring in Peru, was also studied and the authors were able to demonstrate that this disease is due to a species of Leishmania.As regards the species they say: "For the present at least, from the evidence available we do not feel justified in creating a new species for the parasite discovered by us as the etiological factor of uta."A wise decision in view of the present unsatisfactory classification of the Leishmanias.The report also contains a description of a new Linguatulid parasitic in the crocodile, in Equador, which Wheeler has named Poracephalus crocodili; a discussion by Brues of the flies of the family Phoridea obtained by the expedition, and some notes on Peruvian mosquitoes and mosquito literature, by Knab.