Giardia duodenalis cysts isolated from wild moose and reindeer in Norway: genetic characterization by PCR-rflp and sequence analysis at two genes.

There are few genotyping studies of Giardia duodenalis isolates from cervid hosts, although a previous study suggested that cervids may be a source of infection for humans and cattle. Giardia duodenalis isolates collected from wild moose (Alces alces) and reindeer (Rangifer tarandus) in Norway during 2002 and 2003 were characterized by polymerase chain reaction-restriction fraction length polymorphism (PCR-RFLP) at the beta-giardin gene, and sequence analysis at both the beta-giardin and glutamate dehydrogenase (gdh) genes. All results suggested that these isolates (n=25) belonged to assemblage A. Three different restriction patterns were obtained with PCR-RFLP, one of which has previously been associated with assemblage A. At the beta-giardin gene, sequences from six reindeer isolates and one moose isolate were identical to a previously published assemblage A sequence from G. duodenalis cysts isolated from dairy calves. The other 10 moose isolates could be divided into five groups, with between two and 14 single nucleotide polymorphisms (SNPs) from the published genotype A2. At the gdh gene, three different sequences were obtained, differing from each other by between one and 15 SNPs and which have all been previously published as genotype A1, but with different specific hosts. Grouping of the isolates based on the sequences from both genes gave complex results; whereas all the G. duodenalis isolates from reindeer grouped together, two moose isolates, which had identical sequences at the beta-giardin gene, had sequences that differed from each other by 15 SNPs at the gdh gene. The results of these studies, together with the large Norwegian populations of these cervids and the amount of fecal matter they produce, indicate that moose and reindeer may be significant reservoirs of G. duodenalis infection in Norway, which may be of importance to veterinary and public health.