Genetic Diversity of Giardia duodenalis: Multilocus Genotyping Reveals Zoonotic Potential between Clinical and Environmental Sources in a Metropolitan Region of Brazil

Abstract

Background Giardia duodenalis is a flagellate protozoan that parasitizes humans and several other mammals. Protozoan contamination has been regularly documented at important environmental sites, although most of these studies were performed at the species level. There is a lack of studies that correlate environmental contamination and clinical infections in the same region. The aim of this study is to evaluate the genetic diversity of a set of clinical and environmental samples and to use the obtained data to characterize the genetic profile of the distribution of G. duodenalis and the potential for zoonotic transmission in a metropolitan region of Brazil.Methodology/Principal FindingsThe genetic assemblages and subtypes of G. duodenalis isolates obtained from hospitals, a veterinary clinic, a day-care center and important environmental sites were determined via multilocus sequence-based genotyping using three unlinked gene loci. Cysts of Giardia were detected at all of the environmental sites. Mixed assemblages were detected in 25% of the total samples, and an elevated number of haplotypes was identified. The main haplotypes were shared among the groups, and new subtypes were identified at all loci. Ten multilocus genotypes were identified: 7 for assemblage A and 3 for assemblage B.Conclusions/SignificanceThere is persistent G. duodenalis contamination at important environmental sites in the city. The identified mixed assemblages likely represent mixed infections, suggesting high endemicity of Giardia in these hosts. Most Giardia isolates obtained in this study displayed zoonotic potential. The high degree of genetic diversity in the isolates obtained from both clinical and environmental samples suggests that multiple sources of infection are likely responsible for the detected contamination events. The finding that many multilocus genotypes (MLGs) and haplotypes are shared by different groups suggests that these sources of infection may be related and indicates that there is a notable risk of human infection caused by Giardia in this region.

Occurrence and multilocus genotyping of Giardia duodenalis in captive non-human primates from 12 zoos in China

“…In this study, all the G. duodenalis-positive specimens were assemblage B, which is consistent with previous studies [15,16,18]. Assemblage B is common in humans worldwide [6,17,27,28]; therefore, NHPs may contribute to sporadic human infection [23,24]. Of the 25 G. duodenalis-positive specimens, the bg, tpi, and gdh loci were successfully amplified and sequenced from 21, 21, and 20 specimens, respectively ( Table 3).…”

“…Compared with other countries, the average infection rate in this study was closed to that in Thailand (7.0%, 14/200) [9] and Uganda (11.1%, 9/81) [10], but lower than that in North-West India (31.2%, 53/170) [11]. The differences of infection rates in NHPs may be related to animal health status, detection methods, or geo-ecological conditions [2,8,15,16,[22][23][24][25][26][27][28][29]. Nested PCR protocols based on single-copy genes (bg, tpi and gdh) had considerable lower diagnostic sensitivities than those based on multiple-copy genes (e.g.…”

Predominance of Giardia duodenalis Assemblage AII in Fresh Leafy Vegetables from a Market in Southern Brazil

“…Despite the efforts to relate the subgroups to the symptoms of giardiasis, conflicting results have been observed, and to date, there is no definitive correlation between the genotype and clinical symptoms (1). However, the AI genotype has been frequently reported in infected animals, whereas genotype AII has been observed in humans (2, 23) and might be responsible for clinical symptoms of giardiasis, including diarrhea (9,13,17). Colli et al (3) observed the presence of subgroup BIV in 2 (18.18%) of 11 positive vegetable samples, as well as in human samples in the same municipality, in a region near the one sampled in the present study.…”

“…Subgroup AII predominated in our samples, and subassemblages AI, AII, BIII, and BIV are potentially zoonotic (9). Despite the efforts to relate the subgroups to the symptoms of giardiasis, conflicting results have been observed, and to date, there is no definitive correlation between the genotype and clinical symptoms (1).…”

Genotyping ofGiardia duodenalisisolates in asymptomatic children attending daycare centre: evidence of high risk for anthroponotic transmission

“…In South America, most studies have focused on childhood infections and both assemblages have been identified [9,10,18,19], with a predominance of assemblage B [9,18,19]. In Brazil, assemblages A and B have also been recovered from human infections in different populations including children [14,[20][21][22][23], hospital patients [22,24,25] and fishing village populations [26]. Assemblages A and B sequences have been further classified to subassemblages AI, AII, BIII and BIV.…”