COMPARISON OF THE LEVELS OF INTRA-SPECIFIC GENETIC-VARIATION WITHIN GIARDIA-MURIS AND GIARDIA-INTESTINALIS

The extent of intra-specific genetic variation between isolates of Gia rdia muris was assessed by allozyme electrophoresis. Additionally, the levels of allozymic variation detected within G. muris were compared with those observed between members of the two major assemblages of th e morphologically distinct species Giardia intestinalis. Four isolates of G. muris were analysed. Three (Ad-120, -150, -151) were isolated f rom mice in Australia, while the fourth (R-T) was isolated from a gold en hamster in North America. The ii isolates of G. intestinalis (Ad-1, -12, -2, -62, representing genetic Groups I and II of Assemblage A an d BAH-12, BRIS/87/HEPU/694, Ad-19, -22, -28, -45, -52, representing ge netic Groups III and IV of Assemblage B) were from humans in Australia . Intra-specific genetic Variation was detected between G. muris isola tes at four of the 23 enzyme loci examined. Similar levels of Variatio n were found within the genetic groups that comprise Assemblages A and B of G. intestinalis. These levels of intra-specific variation are si milar to those observed within other morphologically-distinct species of protozoan parasites. We suggest that the magnitude of the genetic d ifferences detected within G. muris provides an indication of the rang e of genetic variation within other species of Giardia and that this c an be used as a model to delineate morphologically similar but genetic ally distinct (cryptic) species within this genus. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd.