Heterophyes heterophyes, v. Sieb., 1852.
Syn.: Distomum heterophyes, v. Siebold, 1852; Heterophyes ægyptica, Cobbold, 1866; Mesogonimus heterophyes, Railliet, 1890; Cœnogonimus heterophyes, Looss 1900; Cotylogonimus heterophyes, Braun, 1901.
Length up to 2 mm., breadth 0·4 mm.; the neck not sharply defined; in life it stretches to double the length of the hind body. The scales are rectangular, 5 µ to 6 µ by 4 µ, their posterior margin serrate with seven to nine teeth. Cuticular glands are numerous on the ventral surface, especially in the fore part of the body, and partly discharge at the anterior border of the oral sucker. The oral sucker is 0·09 mm., the ventral sucker 0·23 mm. in diameter; the pharynx measures 0·05 to 0·07 mm. in length; the œsophagus is about three times as long; posteriorly the intestinal cæca are directed one towards the other and terminate beside the excretory bladder. Close in front of the posterior ends of the intestinal branches are the two elliptical testes, which are not exactly on the same level. In the middle in front of them is the receptaculum seminis, and in front of the latter lies the spherical or elliptical ovary. The two vasa efferentia unite to form the vas deferens, which after a short course passes over into the angularly bent seminal vesicle; after the entry of the prostatic glands it becomes united with the metraterm (vagina), and the common duct opens into the genital sucker. The latter is somewhat smaller than the ventral sucker, lateral to and close (0·15 mm.) behind it, and bears a not entirely closed ring of from seventy-five to eighty chitinous rods (20 µ in length). The vitellaria on either side consist of about fourteen acini. The uterus is spread almost throughout the entire posterior part of the body. The eggs have thick shells with a knob resembling that of Clonorchis eggs but not so prominent, and measure 30 µ by 17 µ; they contain a completely ciliated miracidium with a rudimentary intestinal sac.
Fig. 163.—Heterophyes heterophyes, v. Sieb. C., cerebral ganglion; I., intestinal cæca; Ct.g., cuticular glands; V.sc., vitellaria; Ut., genital sucker; T., testes—the excretory bladder between them; L.c., Laurer’s canal; R.s., receptaculum seminis, with the ovary in front of it; G.c., ventral sucker; Vs., vesicula seminalis, 53/1. On the left side above, an egg, 700/1, is depicted, and below it three chitinous rodlets from the genital sucker. 700/1. (After Looss.)
This species was discovered in 1851 by Bilharz in the intestine of a boy who died in Cairo; a second case was only found in 1891 and published by R. Blanchard, so that it appeared as if the species were very scarce. According to Looss, this is, however, not the case, but the species easily escapes notice on account of its small size. Looss found it in Alexandria twice in nine autopsies, and once in Cairo, and has recently stated that in man “it is not at all uncommon to meet with the parasite in cadavers, and the eggs of the worm in the stools of the patients.” Leiper records one case from Japan and one from China. The parasites occupy the middle third of the small intestine, and even when present in large numbers appear to be harmless.
This small species, according to Looss, frequently occurs in Egyptian dogs, less so in cats, and has also been found in the fox, as well as once in Milvus parasiticus; Janson also reports this species from the intestine of the dog in Japan.