Schistosoma mansoni : comparative studies on normal and unisexual infections
A comparative study was made between normal and unisexual S. mansoni infections to investigate interrelations between male and female parasites. Unisexual infections were successfully maintained in the snail Biomphalaria glabrata and in MF1 mice for a period of one year. Male S. mansoni from unisexual infections were of comparable size to males from bisexual infections, but females in the absence of males failed to grow beyond 49 days post-infection in the mouse and remained sexually immature over a period of one year in isolation. While bisexual infections in the mouse demonstrated hypochromic, microcytic anaemia with haemorrhage and portal hypertension as a result of pathogenesis associated with deposition of eggs in the host liver, the anaemia found in unisexual male infections was mild and developed late in infection. Unisexual female infections appeared to be comparatively non-pathogenic. A study of the nutritional interrelationship between male and female S. mansoni by SDS PAGE electrophoresis of protein components, revealed no major differences between the sexes. A particular protein under investigation (molecular wt. 66kDa) previously thought to be male-specific, was detected in all stages of S. mansoni under study, indicating that no major transfer of nutrients from male to female S. mansoni is occurring. Evidence was presented for the role of chemical messengers in relation to worm pairing and female reproductive morphogenesis. Results from staggered unisexual infections indicated possible release of chemicals from male worms which stimulated partial growth and vitellogenesis in unpaired females in vivo. Ecdy-steroids were detected in tissue extracts of male and female S. mansoni from bisexual and unisexual infections and their possible involvement in schistosome development is discussed. Investigation into the antiparasitic effects of the immunosuppressant drug cyclosporin A (CsA) showed the drug to be highly antischistosomal both therapeutically and prophylactically. Evidence from in vitro skin penetration of CsA-treated mouse skin suggests that the skin represents a major site of parasite attrition. The potential of CsA and other cyclosporin analogues for use in the prevention and treatment of human schistosomiasis is discussed.