From 1895 to 1901, Stiles kept insisting that hookworm disease should be of frequent occurrence in the U. S.
A. J. Smith found several cases in persons living in Texas and recognized the fact that these hookworms were different from those of Europe. It was from a study of material from Smith and Claytor in the U. S. and, later on, from Ashford in Porto Rico, that Stiles, in 1902, reported a new genus of hookworm as existing in man. It was first named Uncinaria americana but Uncinaria, belonging to the hookworm of the fox, was not valid, so he changed the name to Necator americanus.
Fig. 88.—Geographical distribution of Ancylostomiasis. Stars show where disease is widely prevalent. Triangles, where less so.
Geographical Distribution.—The disease is rare outside the tropical and subtropical countries except in mines or tunnels where suitable conditions of warmth and moisture exist.
It is extremely prevalent in India and Egypt as well as in China and other parts of the East. It is a very important infection in Porto Rico and the Philippine Islands. It is extensively distributed in South America, especially Brazil, as well as in Central America, Mexico and the Southern States of the U. S. The inhabitants of many of the islands of the Pacific are heavily infested. Hookworm disease is common in southern Europe.
Etiology and Epidemiology
Etiology.—The hookworm infections of man come almost entirely from two parasites, Ancylostoma duodenale, the Old World species, and Necator americanus, which is generally called the New World species from its having first been reported from the U. S. by Stiles. Hookworms belong to the class Nematoda and family Strongylidae.
Quite recently Lane has reported a new species, A. ceylanicum, as having been obtained from 3 men in Bengal, after treatment. This species is the one that infects the civet cat in Ceylon. So far as we know the other human species belong solely to man.