An account is given of field studies carried out at Lake Lindoe in Central Celebes where a remarkable endemic focus of echinostomiasis was first discovered by Brug and Tesch in 1937. In three villages the incidence of infestation was found to be 96, 44, and 24 per cent. The parasites are rapidly expelled by tetrachlorethylene medication and as many as 250 worms have been recovered after a single treatment. The species is characterized by the possession of 37 collar spines; in this respect it resembles Echinostoma revolutum Froelich more than it does any other member of the Echinostomidae recorded from man. While the morphological features whereby the marita stage may be distinguished from that of E. revolutum are not striking, it appears that more tangible differences may be recognized in the redia and cercaria stages. At Lake Lindoe larval development was found in natural infections of a small planorbid, Anisus (Gyraulus) sarasinorum; the metacercaria was found in several pulmonate snails, e.g., Viviparus javanicus rudipellis and also in the mussel, Corbicula lindoensis Boll., which occurs in large numbers in certain parts of the lake. These mussels form a regular part of the diet and the echinostome infection rates in the 3 villages is proportionate to the distances that the villages have to travel to procure mussels for the pot and, by the same token, to pollute the lake so as to bring about infection of the mussels.
Infection of man with the production of the characteristic worms followed the ingestion of mussels. Rats and mice have also been experimentally infected, but the worms do not grow as large as they do in man and the worms are spontaneously expelled a few weeks after attaining maturity.
Reservoir hosts were sought among several species of aquatic birds that frequent Lake Lindoe and in several species of rats found in domestic surroundings with negative results. Attempts to infect chickens were also unsuccessful. These biological considerations fortify the minor morphological differences between E. revolutum and the subject of this paper, which is consequently distinguished by the name Echinostoma lindoensis n. sp.
Formerly Fellow of the John Simon Guggenheim Memorial Foundation.