A contribution to the study of acute schistosomiasis (an experimental trial)

Abstract

In an attempt to establish an experimental model of acute schistosomiasis, sequential histological changes were investigated in the skin, lung, liver and spleen of mice infected with 30 or 100 cercariae of Schistosoma mansoni according to four sets of experiments: single infection, repeated infections, unisexual infection and infection in mice born from infected mothers. Animals were killed every other day from exposure up to 50 days after infection. Only mild, isolated, focal inflammatory changes were found before the appearance of mature eggs in the liver, even when repeated infections were made. Severe changes of reactive hepatitis and splenitis appeared suddenly when the first mature eggs were deposited, around the 37th to 42nd day after infection. The mature eggs induced lytic and coagulative necrosis of hepatocytes around them which was soon followed by dense infiltration of eosinophils. So, mature egg-induced lesions appeared as the major factors in the pathogenesis of acute schistosomiasis in mice. Mice born from infected mothers were apparently able to rapidly modulate the egg-lesions, forming early fibrotic granulomas. The murine model of acute schistosomiasis appeared adequate for the study of pathology and pathogenesis of acute schistosomiasis.

Immunopathology of Schistosoma mansoni infection

“…In experimental studies, sequential histologic examination of infected mice showed severe reactive hepatitis around the first eggs deposited in the liver. Microvacuolated hepatocytes were visible adjacent to the eggs, coagulative necrosis was evident, and the area was surrounded by eosinophils (9 (215). Clinical manifestations seen in patients, i.e., skin rash, eosinophilia, pulmonary edema, or diarrhea, are consistent with this contention (36,106,234).…”

Histopathological study of Schistosoma mansoni infection in the murine model using the PC (Pará) and LILA (Maranhão) strains

“…Andrade and Azevedo (1987) however assert that, before the egg-depositing, only small and isolated changes could be seen in the hepatic parenchyma of mice infected with cercariae of the Feira de Santana (BA) strain of S. mansoni. Severe alterations of reactional hepatitis and necrotic-exudative reactions were only first observed on the 37th day of infection, when the first eggs of the trematode were found in the liver.…”

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

“…Most studies concerned monkeys where both unisexual male trickle infection (Vogel and Minning 1953) and bisexual trickle infection (Webbe and James 1973;Cheever and Duvall 1974;Damian et al 1981;Sturrock et al 1984;Reid et al 1995;Farah et al 1997) induced a convincing protective effect to a bisexual challenge. Trickle infections on mice also induced a convincing protective effect but only concerned repeated bisexual infections (el-Garem et al 1970;Moloney et al 1984;Andrade and Mauadie de Azevedo 1987;Lewis et al 1987;Coelho et al 1995). The protective effect of unisexual male or female trickle infections on mice has never been tested.…”