Differentiation between mixed infection and recombination, key to the zoonotic potential of the protozoan parasite Giardia duodenalis

Abstract

Human giardiasis is caused by two assemblages (A and B) of Giardia duodenalis, which have a worldwide distribution and are also associated with infection of other mammalian hosts. To investigate the zoönotic potential of Giardia duodenalis, a highly specific and sensitive real-time PCR assay was developed. This assay is based on 6 different loci from a region of 50 kb centered around the triose phosphate isomerase gene. Assemblage specific primers were designed and tested on 51 Swedish fecal DNA samples, tested positive for Giardia duodenalis with several other techniques.

The specificity of the assays was found to be 100% (i.e., no cross-reaction observed), the sensitivity was in the range of 5-10 copies (equivalent to 1-2 trophozoites). In 6 of the 51 samples (12%) we confirmed the presence of a mixed infection, assemblage A and B present in one sample.

The newly developed qPCR is a reliable detection technique for assemblage A and B in human fecal samples. Future research will provide useful information on the prevalence of mixed infections and the identification of possible recombinants.