BIOLOGICAL AND GENETIC-ANALYSIS OF A LONGITUDINAL COLLECTION OF GIARDIA SAMPLES DERIVED FROM HUMANS

Duodenal aspirates from children investigated for diarrhoea have been examined for the presence of Giardia over an eleven year period, and w here possible, in vitro or in vivo Giardia cultures in mice were estab lished. Based on biochemical characteristics of electrophoretic karyot ype, RFLP analysis and rDNA hybridization studies of 40 stocks at leas t two major varieties, or demes, of Giardia have infected the populati on of South East Queensland and environs during this period. These dem es carried different rDNA repeat units and differed markedly in both t he electrophoretic karyotype pattern and the molar representation of c hromosome bands. From 1983 to 1991 only one deme was documented. The f irst evidence of a new deme seen in local children occurred in 1991 an d was followed by a predominance of this deme in 1993. These 40 stocks do not represent all positive samples. Other stocks established in vi vo were not able to be cultured in vitro, and these probably represent other demes. Since all of the stocks were derived from children with similar chronic symptoms it appears that at least two demes of Giardia are pathogenic.