Epidemiological and molecular evidence supports the zoonotic transmission ofGiardiaamong humans and dogs living in the same community

Abstract

Giardia duodenalisisolates recovered from humans and dogs living in the same locality in a remote tea-growing community of northeast India were characterized at 3 different loci; the SSU-rDNA, elongation factor 1-alpha (ef1-α) and triose phosphate isomerase (tpi) gene. Phylogenetic analysis of the SSU-rDNA and ef1-α genes provided poor genetic resolution of the isolates within various assemblages, stressing the importance of using multiple loci when inferring genotypes toGiardia. Analysis of the tpi gene provided better genetic resolution and placed canineGiardiaisolates within the genetic groupings of human isolates (Assemblages A and B). Further evidence for zoonotic transmission was supported by epidemiological data showing a highly significant association between the prevalence ofGiardiain humans and presence of aGiardia-positive dog in the same household (odds ratio 3·01, 95% CI, 1·11, 8·39,P=0·0000).