For a number of years Japanese physicians had noted the existence of a disease characterized by splenic and hepatic enlargement, ascites and cachexia. In August, 1904, Katsurada discovered ova with a ciliated embryo in the stools of patients with this disease. He found schistosomes in the portal vessels of dogs and cats containing eggs similar to those seen in the human cases. He named this trematode S. japonicum. In November, 1904, Catto discovered the parasite at an autopsy on a Chinaman. In 1910 Lambert, in China, described a disease, which he called urticarial fever, and a short time afterward Houghton established the connection between this disease and the more advanced stages of Japanese schistosomiasis.
Fig. 108.—Ovum of Schistosoma haematobium. By William Pepper. (Jefferys and Maxwell.)
Fig. 109.—Ovum of Schistosoma mansoni. By William Pepper. (Jefferys and Maxwell.)
Pathology
The pathological lesions are almost entirely due to the irritation of the eggs with resulting connective tissue increase or ulcerative processes. For some reason these flukes select the inferior mesenteric vein and make their way to the vesical plexus of veins in the case of S. haematobium and to the haemorrhoidal vessels for the other species. At times the ova or worms may be carried over to the systemic veins by way of the channels of anastomosis. In the terminal vessels the female gives off the eggs which penetrate the adjacent mucosa giving rise to inflammatory thickenings and the extrusion of the irritating eggs into the lumen of the bladder or rectum.
In the bladder these terminal spined eggs cause haematuria and form the nucleus for vesical calculi. The mucosa may also show wart-like excrescences. If the eggs are swept back through the portal vessels to the liver an interlobular cirrhosis results which would seem to be due entirely to the irritation of these egg emboli and not to toxic products of the worms themselves. Marked ureteral and kidney lesions may result as complications of cystitis or primarily from irritation by ova. In women the vagina, vulva and cervix uteri may show papillomatous thickenings. Bilharzial lesions of the male urethra are not uncommon and may lead to fibroid thickenings and fistula.