Studies on schistosomiasis in Southern Rhodesia

Abstract

The results embodied in the following report were obtained in the course of a general helminthological survey of Southern Rhodesia during the year 1930. The work was undertaken on behalf of the London School of Hygiene and Tropical Medicine which, in conjunction with the Government of Southern Rhodesia, has established a Rhodesian Research Fellowship for the purpose of facilitating the investigation of disease conditions in the Colony. The present investigation was begun in May 1930 and continued until February 1931.

When the work commenced schistosome infestations were known to be present both in the Europeans and the Natives of the Colony. From the clinical standpoint, however, the disease was regarded as relatively unimportant as the gross manifestations of the disease, either in its urinary or intestinal form were rarely encountered.

Precise knowledge was lacking on the intermediate molluscan hosts of the schistosome species met with in Rhodesia. Various fresh -water molluscs had, from time to time, been submitted to the Public Health Laboratory, Salisbury, but no animal experimentation had been carried out to determine the nature of the cercariae they chanced to harbour.

The possibility of the existence of reservoir hosts for mammalian schistosomes capable of parasitising man had not been investigated.

In the course of a few preliminary examinations it soon became apparent that schistosome infestations were much more prevalent amongst the Native population than had been hitherto suspected and on this account it was decided to devote as much of the available time as possible to a study of the schistosome problem.

While determining the incidence of the infestation amongst the Natives of the different regions of Southern Rhodesia, every opportunity was taken to investigate the bionomics of those fresh -water molluscs which constituted the intermediate hosts of the parasites. At the same time frequent autopsies were carried out on various mammals, such as monkeys, baboons, sheep, etc., for the purpose of detecting previously unsuspected hosts for the human schistosomes.