This parasite is white and filiform, 4 to 12 mm. long and 0.2 to 0.6 mm. thick (Fig. 58). The males are much smaller than the females. The oxyuris has three small knoblike lips. The female possesses two uteri passing backward and forward from the end of the vagina. The opening of the latter is situated above the middle of the body. The eggs are 0.05 mm. long and 0.02 wide. The contents are granular and the shell appears white.

Oxyuris Vermicularis: a, natural size; b

Fig. 58. - Oxyuris Vermicularis: a, natural size; b. head; c, tail, magnified; d, head greatly magnified.

Infection takes place when the eggs of oxyuris reach the stomach. Here the shell opens and the embryo migrates into the small intestine (Fig. 59). After fructification has taken place the females usually begin to wander along the intestinal canal. In the caecum they generally make quite a long sojourn until the eggs are almost ripe. Then they again begin to pass downward. According t o Leichtenstern, Lutz, and Huber, the females do not pass their eggs within the intestinal canal. As a rule they first leave the bowel and then deposit the eggs. For this reason the fecal matter usually does not contain any eggs.

Development of Oxyuris Vermicularis

Fig. 59. - Development of Oxyuris Vermicularis. (Heller.) a-e, Segmentation of the yolk; f. ovum containing tadpole-shaped embryo, seen from the side: g, abdominal view of the same; h, ovum with worm-shaped embryo; i, embryo escaping from the shell; k free embryo capable of motion.

The symptoms which are most frequently observed consist in pronounced pruritus ani due to the irritation produced by the passing of the parasites out from the rectum. Frequently the itching annoys the patient as soon as he retires. Various nervous symptoms are occasionally observed: anorexia, nausea, dizziness, palpitation of the heart, pollutions and spermatorrhoea in the male; besides diarrhoea occasionally occurs. Pronounced anaemia is encountered, although rarely. In rare instances the parasites reach the vagina and cause irritation there. Nymphomania has then been observed.

Infection probably occurs through direct conveyance of the eggs by the unwashed hands of the host. It is also possible that ova dried by the sun exist on fruit, radishes, or salads, in which state they may be carried into the stomach.

The diagnosis of the thread worm is made by inspection of the anal region and by the finding of the oxyuris.

With regard to prophylaxis extreme cleanliness is of the greatest importance. Fruits should be thoroughly cleaned and then peeled before they are eaten. The eating utensils of a person infected with oxyuris should never be used by another, unless they have been thoroughly disinfected. The same applies to the clothes. Sleeping with an infected person should be forbidden, and even touching his hands requires immediate washing, as otherwise infection may take place.

Treatment

Santonin is the principal remedy for combating oxyuriasis. It is given in the same way as described in the treatment of ascaris lumbricoides. Here, however, irrigations of the bowel with water and the addition of a few drops of benzene or thymol or vinegar (three to four tablespoonful to a quart), or of sapo medicatus in a one-half to one-per-cent solution may be advantageously used. The anal region should be thoroughly cleansed. If the pruritus ani is quite intense, application to the anal region and rectum of unguentum hydrarg. cinerei or the use of a suppository of ung. hydrarg. cinerei 1 gm., in cacao butter 2 gm. will afford relief.