The relation of these parasites to certain diseases of domestic animals has been studied by veterinary surgeons. Sarcosporidia may cause fatal epizoötics among sheep.
There is still a wide field open for research in regard to the structure and development of these parasites, and the manner in which the hosts become infected.
Fig. 102.—Longitudinal section of a muscle of the domestic pig, with Sarcocystis miescheriana. × 30. (After Kühn.)
Fig. 103.—Transverse section of the muscle of a pig, with Sarcocystis miescheriana. × 38. (After Kühn.)
The Sarcosporidia usually appear as elongate, cylindrical, or fusiform bodies, rounded at both extremities and of various lengths and breadths (fig. 102). In some species they may be from 16 mm. to 50 mm. long, as in the sheep and roebuck. These bodies are the so-called sarcocysts or Miescher’s tubes. They lie in transversely striated muscular fibres which they distend more or less. The forms found in the connective tissue are apparently parasites which originally inhabited the muscular fibres, and only on disintegration of the fibres reached the connective tissue, where they grow to large oval or globular bodies (fig. [105]). The mammalian muscles usually infected are those of the œsophagus, larynx, diaphragm, body-wall, and the psoas muscles. The skeletal muscles may be affected in acute cases, as well as those of the tongue and eye. The heart muscles are sometimes parasitized.