Abstract
In Puerto Rico man is the only known definitive host of Schistosoma mansoni infection. The experimental data included in this report are based on infections of laboratory rats and rabbits and rhesus monkeys, as well as on one accidental human infection. Twenty-three rats, 8 rabbits and 4 monkeys were submitted to inoculation, either by placing the animal for one to 2 hours in a bath of water swarming with cercaria, or by placing desirable food in such water, or by spraying infected water into the animal's mouth. Evidence that cercariae were attacking the animal's skin within an hour after exposure was furnished by the extreme nervousness and later by intense pruritus of the exposed tissue of the animal. This continued for several hours after the animals were removed from the infective bath. All animals exposed became infected. The animals were sacrificed under anesthesia at intervals varying from 16 hours to 70 days, the cavities were opened, the various organs and tissues carefully inspected for gross evidence of infection and then the several organs were separated by ligation and removed from the body into isotonic citrate solution. These tissues and organs were thoroughly perfused and/or chopped up and the solution centrifuged and then examined for migrating larvae. Likewise, suitable portions of each organ were fixed in Zenker's fluid and sectioned. By these methods it was found possible to trace the route of migration and development of the young worms day by day through the prepatent period.
In general the development follows that described by various workers for Schistosoma japonicum, the Oriental blood fluke, but with important exceptions. The migration route is as follows. Entry of the cercariae through the skin takes place within a few hours after exposure. Within 16–20 hours after inoculation the larvae have left the skin, most usually via the peripheral veins, but at times passing through peripheral lymph nodes.
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