Studies on migration, development and the fate of schistosoma mansoni in the Laboratory rat

Abstract

Previous studies have shown that the rat is not a permissive host of Schistosoma mansoni. More cercariae die in the skin of this host during penetration than in the permissive laboratory hosts such as mice and hamsters; the worms which grow in this host are usually stunted; and they inhab:t the liver and produce relatively few eggs which give rise to non-viable miracidia. Also it has been observed that there is always a rapid drop in the number of worms recovered by perfusion after the fourth week of infection. However, there are still many gaps in our knbwledge of the biology of this parasite in this particular host. In this study attempts were made: to trace the route(s) of migration of the schistosome from the lungs to the liver; to study its development; and to determine the fate of the worms which apP?rently disappear from the liver of this host after the fourth week of infection. Results of these investigations have shown that: S, mansoni migrates from the lungs to the liver mainly through the blood vascular system; and that, a few parasites may migrate through the pleural ti~ue, into the pleural cavity, across the diaphragm, into the peritoneal cavity, and thence into the liver; but there was no evidence of the use of any other route(s), The development of the parasite in the rat ~s the same as that occuring ~n the mouse (a permissive hostof the parasite) upto around the twenty-eighth day, Thereafter development, particularly that of the female worms appears to be delayed, and is completed around the forty-second day of development. Most of the worms which appear to disappear from the liver of this host, actually rema~n trapped ~n blood vessels of the organ and therefore can not be recovered by perfusiono He re they induce a leucocytic inflammatory reaction, involving mainly eosinophils, macrophages and lymphocytes, which eventually destroys them. A few of the "disappearing", worms are carried in the ~loodstream to other parts of the body such as the heart and