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 the detection and characterisation of variants within the human schistosomes and the implications of this variation in terms of infectivity and development in intermediate and definitive hosts, drug responsiveness, pathogenicity and immunogenicity. It also examines advances in the methods used to detect variation and highlights the use of genetic approaches, notably enzyme electrophoresis and, especially, the recent application of DNA methods. Molecular techniques, such as restriction fragment length polymorphism (RFLP) analysis, polymerase chain reaction (PCR) and DNA sequencing are now proving invaluable for distinguishing species and strains of schistosomes and recent progress in this remarkably dynamic area is emphasised.