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844

Synonyms.—Amphistomum watsoni; Cladorchis watsoni; Paramphistomum watsoni.

History.—This parasite was found in 1904 by Watson in the duodenum and upper part of the jejunum of a negro patient from German West Africa who died of starvation and diarrhœa. The stools were numerous, watery, and of a bilious colour, and contained many yellow, translucent, oval trematodes. At the post-mortem the jejunum was found to be full of these trematodes, some of them alive and still adherent. The mucosa showed no hæmorrhages, but appeared to be slightly congested. The other parts of the bowel, as also the other organs, were normal. The parasite is said to occur in monkeys and to be common in natives near Lake Tchad.

The parasite.—W. watsoni (Fig. 191) is of a reddish-brown colour and measures 8 to 10 mm. in length by 4 to 5 mm. in breadth; it is oval in shape. The oral sucker is small; the ventral sucker or acetabulum large and at the posterior extremity of the body. The genital pore opens at the anterior end of the ventral surface on a level with the bifurcation of the intestine. The ova measure 125 μ in length by 75 μ in breadth.

Life-history.—We know nothing of the life-history of this parasite, but probably it is similar to that of P. cervi, the conical fluke of cattle and sheep, which was thoroughly worked out by Looss in 1896. The eggs of P. cervi contain a ciliated embryo (miracidium) which escapes from the eggshell under the stimulus of light and moisture. Swimming about in the water, which it must necessarily reach for further