This important parasite was first described by Dubini 1 in 1838. Bilharz 2 and Griesinger3 recognized this parasite as the cause of the Egyptian chlorosis. Some time afterward the anchylostoma was observed in severe cases of anaemia among workmen in tunnels and brickmakers.

The anchylostoma duodenale is cylindrical in shape, 0.5 to 1 mm. thick and 6 to 18 mm. long. It is yellowish or grayish-white in color, with translucent edges. The male is much shorter than the female. The cephalic end is curved toward the dorsal surface and is provided with an oral capsule at the margin of which there are six hooklike teeth. Further within the capsule there are three sharp chitinous processes (Figs. 60 and 61). The male is more slender and transparent than the female. Its head end is bent backward. The tail end appears somewhat swollen, containing the bursa copulatrix, and is much more curved than the head. In the female the caudal end is pointed and armed with an awl-like prong; the genital opening lies behind the centre of the body. The eggs are oval, 0.06 mm. in length and 0.03 mm. in width (Fig. 62).

1 Angelo Dubini: Gaz. med. Lombard., 1843.

2 Bilharz: Wiener med. Wochenscbr., 1856.

3 Griesinger: Arcb. f. physiolog. Heilkunde, 1854.

Male of Anchylostoma Duodenale

Fig. 60. - Male of Anchylostoma Duodenale. (Schultheiss.) a. Head with mouth-capsule; b, oesophagus; c, intestine; d. anal glands; e, cervical glands; f, skin; g, muscular layer; h, porus excretorius: i. triple bursa; k, ribs of the bursa; /, testicular canal; m, vesicula seniinalis; u, ductus ejaculatorius; o, groove of latter; p, penis; q, sheath of penis. Magnified 30 diameters.

Cephalic End of Anchylostoma Duodenale

Fig. 61. - Cephalic End of Anchylostoma Duodenale. (Schultheiss.) a. Mouth-capsule; b, teeth of ventral border; c, teeth of dorsal border; d, buccal cavity: e, skin-sac on ventral side of head; f, muscular layer; g, dorsal groove; h, oesophagus.

Eggs of Anchylostoma Duodenale

Fig. 62. - Eggs of Anchylostoma Duodenale. (Perroncito and Schultheiss.) a, b, c, d. Different stages of cleavage; e, f, eggs with embryos. Magnified 300 diameters.

The habitat of the anchylostoma is the duodenum, the jejunum, and the upper part of the ileum. Here the worm attaches itself to the intestinal mucosa and feeds by sucking the blood of his host. According to Leichtenstern,1 active migration of the worm begins at the time of the first copulation in the fifth week. Young worms change their place quite frequently and hence give rise to repeated hemorrhages. Colic, and acute anaemia are encountered at an early period after infection.

Under favorable conditions the eggs develop outside of the body into rhabditis-like larvae, becoming enclosed in a protecting envelope or encysted. In this stage the larvae may be carried along with the dust and contaminate fruit and water. On reaching the small intestine they develop into mature worms. This parasite is always encountered in great numbers if present in the intestines. Leichten-stern never found them in a smaller number than one hundred, but sometimes their total reached three thousand.

The symptoms produced by anchylostoma consist of gas-tralgia, nausea, occasionally vomiting, constipation, rarely diarrhoea, and severe anaemia, the latter becoming progressively worse. The patient with anchylostoma does not greatly emaciate, but becomes pale, extremely weak, and suffers from dizziness and shortness of breath after the slightest exertion. His extremities are cold, slight hemorrhages occur frequently, and oedema of the ankles develops. A systolic murmur may be heard at the apex of the heart, the pulse is accelerated, and fever may be present toward evening. An inclination to eat earth (geophagia) is not rarely observed.

1 Leichtenstern: Centralbl. f. klin. Medicin, 1885, and Deutsche med. Wochenschr., 1885, 1886, 1887.

The dejecta are of a brownish color, although admixture of blood cannot be recognized macroscopically. Microscopically Charcot-Leyden's crystals, as well as the eggs of the parasites, are often found in the stools. The urine rarely contains albumin, but frequently indican. The condition of the blood resembles that found in pernicious anaemia: enormous decrease of the red blood corpuscles, poikilocytosis, nucleated red blood corpuscles, and a slight increase of the leukocytes, especially of the eosinophile cells.

Anatomically the mucosa of the small intestine is found greatly congested and ecchymoses are visible here and there. Peyer's patches and the solitary follicles are often swollen. The heart is found hypertrophied and dilated, the liver and spleen may be diminished in size, normal, or in an amyloid condition. The same can be said of the kidneys. There is no doubt that the principal deleterious action of the anchylostoma consists in the profuse loss of blood caused by the parasites. Whether some toxic substances generated by them participate in producing the grave symptoms is questionable.

The course of the disease is protracted and its severity depends greatly upon the number of parasites present. If the latter is great, the disease may progress quickly and the patient succumb with the symptoms of general dropsy, dyspnoea, and heart failure or pulmonary oedema. If the number of the parasites is small, the patient may live many years and ultimately recover entirely. Recover}' is also possible by successful expulsion of the parasites from the intestinal tract.

The diagnosis of anchylostomiasis is made by the presence of the symptoms of anaemia in conjunction with the discovery of the anchylostoma eggs in the dejecta.

With regard to prophylaxis the above given rules for the prevention of the round- and thread-worms are also applicable here. Extreme cleanliness of the body and of the food is of greatest importance.

The treatment consists in the administration of extract of male-fern, which should be employed in the same manner as described above for the tapeworm disease.