BILHARZIOSIS 



1927 



and Mesopotamia, and in the West Indies. In Egypt, according to 

 Sandwith, infection probably takes place in the early winter months 

 when the floods have subsided. 



etiology. — The cause of the disease is Schistosoma hcBmatohium. 

 The life-hisfory is described in Chapter XXIV., p. 584. The 

 method of infection is by the cercariae penetrating the skin or 

 mucous membranes and developing into adults, which live and 

 copulate in the portal and vesical veins, while the eggs leave the 

 body with the urine. 



It occurs in any race and at any age, except infancy, but is 

 more common in males than in females, due, it is thought, to the 

 men washing in streams and working in the fields barefooted. 

 According to Miss Elgood's investigations, the disease is common 

 also in young girls, even in those who 

 do not bathe, and who use filtered 

 water. It is rare in Europeans, being 

 much more common among the natives, 

 in whom it is prevalent among the working 

 classes, especially the field-labourers. 



Fig. 778B. — Photographs of Bulinus 

 contorfus. 



Fig. 778A. — MiRAciDiuM 

 OF Schistosoma Hcs- 

 matobiu n. ( x 300 Di- 

 ameters. ) 

 (Photomicrograph.) 



Pathology. — The worms live in the porta 

 vein, but proceed to the venules of the 

 bladder to lay the eggs. The irritation 

 of these eggs excites a round-celled infiltra- 

 tion, sometimes of a very extensive nature, 

 giving rise to a sort of bilharzial granu- 

 lation tissue — that is, a tissue composed of 

 round cells and eggs. Madden divides 

 the pathological changes into two classes — the hypertrophic and the 

 atrophic. In the former, which is more common in mucous mem- 

 branes, there is proliferation of the epithelium, with the formation 

 of flattened projections or papillomata, while vesicles may also form, 

 and, according to Madden, by bursting, give rise to the ulcers which 

 at times are seen. 



The ova may escape from the mucosa, according to Looss, without 

 the aid of ulceration, by working their way between the epithelial 

 cells into the lumen of the viscus. Underneath the mucosae the 

 round-celled infiltration forms the typical bilharzial granulation 

 tissue, and leads to much thickening of the wall of the viscus, and, 

 proceeding to connective-tissue formation, may cause marked 



