Schistosoma japonicun infection in the pig as a model for human schistosomiasis japonica

Valuable information on human schistosomiasis japonica has been provided us ing primates and experimental rodent hosts. However, major drawbacks such a s high costs and ethical concerns for the primate models and large biologic al deviations for the rodent models have led to the search for more appropr iate models. Recent data on the pig indicate that this natural host for Sch istosoma japonicum might be a realistic alternative. As only very few resea rch groups have investigated the S. japonicum/pig model, the present review mainly deals with the experimental methods and the major host/parasite fin dings obtained from the authors own research group. With emphasis on a crit ical evaluation of the work, the results are compared to the scarce informa tion existing on human schistosomiasis japonica. Like in humans, S. japonic um establishes mainly in the large intestinal veins, with high faecal egg c ounts during the acute phase of infection, which varies greatly within and between days. Concomitant resistance is another shared feature, but studies in pigs have indicated that the phenomenon is more complex than generally thought. Clinical signs as eosinophilia and diarrhoea with mucus and blood in the acute phase of infection and hepatomegaly, increased portal diameter , periportal fibrosis and ascites in chronic infections are common findings in both humans and pigs. Low protein diet aggravates the disease in pigs b y increasing the establishment rates, the faecal egg excretion and the morb idity. A 100% cure rate is achieved when treating S. japonicum infected pig s with praziquantel at 40 mg/kg, and 4 weeks post treatment pigs remain res istant to reinfection. Lastly, human congenital S. japonicum infection has been confirmed in pigs but the implications of such infections for the path ogenesis of schistosomiasis japonica remain to be investigated. (C) 2000 El sevier Science B.V. All rights reserved.