MOLECULAR VARIATION IN THE HUMAN SCHISTOSOMES

It is now recognised that intraspecific variation is widespread in the human schistosome species. This review evaluates recent advances in t he detection and characterisation of variants within the human schisto somes and the implications of this variation in terms of infectivity a nd development in intermediate and definitive hosts, drug responsivene ss, pathogenicity and immunogenicity. It also examines advances in the methods used to detect variation and highlights the use of genetic ap proaches, notably enzyme electrophoresis and, especially, the recent a pplication of DNA methods. Molecular techniques, such as restriction f ragment length polymorphism (RFLP) analysis, polymerase chain reaction (PCR) and DNA sequencing are now proving invaluable for distinguishin g species and strains of schistosomes and recent progress in this rema rkably dynamic area is emphasised.