Lesions Caused by Eggs of the Changhua Strain of Schistosoma Japonicum in the Liver of Formosan Monkeys *

Abstract

In the liver of Formosan monkeys infected with the Changhua strain of Schistosoma japonicum, previous investigators found large granulomata with an extensive area of central necrosis, but their nature was not determined. Livers of 17 Formosan monkeys infected with the Changhua strain were studied. Lesions varied greatly according to individual susceptibility. Lesions were caused by single eggs or by a conglomerate of eggs. The single-egg lesion was of usual size, often containing an immature, but occasionally a mature, egg. The immature egg could directly elicit a lesion of the productive stage. In the lesion elicited by a mature egg, vacuolation and liquefaction of giant cells were occasionally seen. The lesion caused by a conglomerate of eggs was many times larger than the lesion with a single egg, and an area of central necrosis, which was encircled by mature eggs, was noted. Worm lesions were found simulating a large lesion due to eggs with central necrosis, but worm remnants could usually be identified. We conclude that the size and morphology of the single-egg lesions in Formosan monkeys infected with the Changhua strain were similar to those of the Japanese strain. Special features in the infection of Formosan monkeys by the Changhua strain were the occurrence of central necrosis in the lesions (especially in the conglomerate-egg lesions), the elicitation of the productive stage of lesions by immature eggs in the early stage of infection, and the great variation of individual susceptibility to the parasite.