MOLECULAR VARIATION IN GIARDIA

Molecular characterisation of species within the genus Giardia has rev ealed that much of the phenotypic heterogeneity, particularly within t he species G. duodenalis, has a genetic basis. The source of this gene tic variation appears to arise from predominantly asexual, clonal repr oduction, although occasional bouts of sexual reproduction cannot be r uled out. Genetic variation is extensive with some clones widely distr ibuted and others seemingly unique and localised to a particular endem ic focus. Little attention has been given to the molecular epidemiolog y of Giardia infections. Future studies should be directed at studying the ecology and dynamics of transmission of Giardia clones, particula rly in localised areas, and to evaluating the factors that serve to ma intain genetic diversity between clones, especially the role of inter- clonal competition. Future research using molecular techniques should aim to identify and follow Giardia clones in nature and correlate gene tic typing with important clinical and epidemiological characteristics such as virulence, drug sensitivity and zoonotic potential.