Pulmonary manifestations of schistosomiasis.

Trematodes of the genus Schistosoma, which occur as parasites in some parts of the venous circulatory system in human beings, are very frequent in Egypt. Infection is almost the rule among Egyptian peasants, and it is estimated that 60 to 70 per cent of the inhabitants are infected. It used to be considered that the affection was limited to the lower urinary and intestinal tracts, with visceral complications limited to the abdominal organs, particularly the liver, spleen, and kidneys. It is only relatively recent that affection of the lungs has attracted attention. Two species of the parasite occur in Egypt. Sch. mansoni inhabits the tributaries of the portal vein, while Sch. haematobium thrives in the vesical, prostatic and uretenic veins. They may, however, occasionally exchange localities, and double infection is frequent. Infection occurs by contact with water which has been contaminated with ova passed by an infected person. The ova hatch out a “miracidium” which then infects a special kind of snail. In this it undergoes further development, and emerges as a “cercarla” which swims about in the water. If a human being comes in contact, the cercarla penetrates the skin, and is carried by the circulation through the lungs to its final habitat where it develops into the adult worm. This lays its eggs in the venules of the bladder or rectum, and during muscular contraction of these organs the ova are expelled into the lumen, from which they escape with the urine or feces. The chief clinical manifestations are the passage of blood in the urine or stools. The most frequent complications are cirrhosis of the liver, urinary tract infection, pyonephrosis and urinary calculi. Historical: Belleli’ reported Bilharzia ova in the lungs in 1885. Symmers2 described Schistosoma worms in the vessels of the lungs in 1905. In 1928 Sorour3 described the pathology of Bilhanizial lesions in the lungs, and further pathological studies were made by Shaw and Abu Ghareeb in 1938.