Fig. 207.—Cross-section of bovine blood fluke (Schistosoma bovis), showing the position of the female in the gynæcophoric canal. × 200. (After Leuckart, 1894, p. 472, Fig. 209.)
If the parasites are lodged in the venous plexus of the genito-urinary system, the chief symptoms are: hæmaturia, pains in the lumbar region, the left iliac fossa, the thigh, or in the vulva, which may be spontaneous or may accompany micturition; cystitis, vesical calculus, urinary fistulæ, vaginal verminous tumours, nephritis.
The eggs accumulate in the capillaries, which they rupture; they traverse the mucosa and fall into the bladder, thus causing more or less hæmorrhage; in this way the hæmaturia is established, which is often the initial symptom. At first the urine is quite bloody, but it gradually becomes clearer, and it is only at the end of micturition that muco-purulent flakes are expelled, in which numerous eggs and even embryos are found; the urine contains also epithelial cells, more or less pus, eggs, and occasionally embryos. On micturition sharp pains are felt at the base of the penis or at the gland, possibly due to the passage of eggs. The passage of eggs through the walls of the bladder gives rise to cystitis; blood becomes more abundant in the urine after fatigue or coitus; clots may form and cause retention of urine; chronic urethritis may develop, evidently due to the presence of the eggs. In Egypt 80 per cent. of the cases of vesical calculus in man coincide with bilharziosis; the formation of the calculi evidently results from the presence of the eggs, for the central nodule always contains one or more of these structures. Urinary fistulæ, opening on the perineum, more rarely into the rectum, occasionally form. The mucosa of the vagina, also of the uterus and bladder, becomes impregnated with calcareous salts. Nephritis develops in grave cases.
Fig. 208.—Eggs of bovine blood fluke (Schistosoma bovis), showing the peculiar process on the end. a, b, Layers of the oviduct; c, eggs in the oviduct × 180; x, eggs deformed by pressure; y, spinous process on end of egg × 700. (After Sonsino.)
If the parasites lodge in the veins of the rectum the lesions caused are analogous to those described for the genito-urinary tract.
The heart, lungs, and liver generally remain normal.
Pathology. The bladder is reduced in size, while its wall is greatly thickened, due chiefly to hypertrophy of the muscularis; the mucosa is also thickened, and at certain points it is indurated by uric or calcareous deposits, but the principal lesion consists in ulcerations covered with sanious pus. Lesions analogous to those of the bladder are also observed in the lower third of the ureters, and may extend as high as the kidney; the ureter is enlarged and tortuous; the mucosa irregular; its lumen may remain nearly normal in size, but its wall becomes very thick: the flow of urine may be obstructed; in short, a veritable hydro-nephrosis obtains, which results in atrophic lesions of the kidney, and may finally end fatally.
The mesenteric lymphatic glands may hypertrophy, their substance becoming tumefied, presenting small hæmorrhagic centres, and containing eggs. The liver may contain eggs and become somewhat cirrhotic; the eggs accumulate in the branches of the portal veins, or after piercing the walls they lie in the hepatic parenchyma. The lungs may also contain eggs.