Fig. 119.—Fasciolopsis buski. Cleared in glycerin. (From Jefferys and Maxwell.)
It seems to be capable of setting up quite an eosinophilia at the time the adult female is penetrating the crypts of Lieberkühn, so that it is probably of pathogenic importance.
Fig. 120.—A, Egg of Strongyloides intestinalis (parasitic mother worm) found in stools of case of chronic diarrhoea; B, Rhabditiform larva of Strongyloides intestinalis from the stools. (William Sydney Thayer, in Journal of Experimental Medicine.)
The parasitic or intestinal form (also known as Anguillula intestinalis) is represented only by females. These are about 1/12 of an inch (2 mm.) long and reproduce parthenogenetically. They have a pointed, four-lipped mouth, and a filariform oesophagus which extends along the anterior fourth of the body. The uterus contains a row of 8 to 10 elliptical eggs which stand out prominently in the posterior part of the body by reason of being almost as wide as the parent worm.
They usually live deep in the mucosa and the embryos emerge from the ova laid in the mucosa. The embryos escape from the eggs while still in the intestines, so that in the faeces we only find actively motile embryos. The eggs, which are strung out in a chain, never appear in the faeces except during purgation. As they greatly resemble hookworm eggs this is a point of great practical importance.
In fresh faeces we find hookworm eggs and Strongyloides embryos. The embryos are rather common in stools in the tropics. These embryos have pointed tails and are about 250 × 13 microns. They have a double oesophageal bulb. They are about 250 microns when they first emerge but may grow until they approximate 500 microns in the faeces. The mouth cavity of the embryo of the hookworm is about as deep as the diameter of the embryo at the posterior end of the mouth cavity; that of Strongyloides is only about one-half as deep as the diameter. If the temperature is low, below 15°C., these rhabditiform embryos develop into filariform embryos, which form the infecting stage.
It has been demonstrated by Fülleborn that infection of man takes place through the skin. If the temperature is warm, 25° to 35°C., these embryos develop into the free-living form. In this we have males and females, with double oesophageal bulbs, the male about 1/30 of an inch (¾ mm.) long with an incurved tail and 2 spicules and the female about 1/25 inch (1 mm.) long with an attenuated tail. These copulate and we have produced rhabditiform larvae, which later change to filariform ones. At this time the length is about 550 microns. These start up the parasitical generation.
For treatment thymol is usually recommended. Stiles speaks highly of sulphur.