Tissue Responses and Mechanisms of Resistance in Schistosomiasis Mansoni in Abnormal Hosts

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Abstract
Summary Detailed histopathological examinations of tissues of resistant and susceptible hosts to Schistosoma mansoni were made to study the mechanism of resistance to schistosomiasis in abnormal hosts. The reaction to initial infections in 13 species of mammalian hosts confirmed the wide spectrum of host parasite relationships outlined by parasitological methods. The Hoeppli phenomenon was observed in the woodchuck. In the opossum eggs for the most part failed to gain access to the intestinal mucosa and the organ loads were very high. In the cottontail rabbit, the liver was the sole target organ and it absorbed nearly the entire egg production of the relatively few adults. In the muskrat, parasite development was stopped before adulthood was reached, but schistosomula reached the lungs where some evoked a granulomatous response and were trapped. In the fox, schistosomula were trapped in the corium and subcutaneous tissue and destroyed in situ. The implications of the striking similarity between the cellular reaction observed in the abnormal hosts and that in immunized laboratory animals was discussed in relation to known humoral and cellular mechanisms of defense.