Multilocus Genotyping of Giardia duodenalis in Mostly Asymptomatic Indigenous People from the Tapirapé Tribe, Brazilian Amazon

Abstract

Little information is available on the occurrence and genetic variability of the diarrhoea-causing enteric protozoan parasite Giardia duodenalis in indigenous communities in Brazil. This cross-sectional epidemiological survey describes the frequency, genotypes, and risk associations for this pathogen in Tapirapé people (Brazilian Amazon) at four sampling campaigns during 2008–2009. Microscopy was used as a screening test, and molecular (PCR and Sanger sequencing) assays targeting the small subunit ribosomal RNA, the glutamate dehydrogenase, the beta-giardin, and the triosephosphate isomerase genes as confirmatory/genotyping methods. Associations between G. duodenalis and sociodemographic and clinical variables were investigated using Chi-squared test and univariable/multivariable logistic regression models. Overall, 574 individuals belonging to six tribes participated in the study, with G. duodenalis prevalence rates varying from 13.5–21.7%. The infection was positively linked to younger age and tribe. Infected children <15 years old reported more frequent gastrointestinal symptoms compared to adults. Assemblage B accounted for three out of four G. duodenalis infections and showed a high genetic diversity. No association between assemblage and age or occurrence of diarrhoea was demonstrated. These data indicate that the most likely source of infection was anthropic and that different pathways (e.g., drinking water) may be involved in the transmission of the parasite.

Giardiasis in urban and rural Amazonas, Brazil is driven by zoonotic and cosmopolitan A and B assemblages

“…(9) A similar scenario occurred among indigenous peoples in Mato Grosso, Midwest Brazil, where assemblage B was also predominant. (10) Globally, most studies showed a higher prevalence of assemblage B (20) with the exception of Australia, where A was predominant. (4) The diversity of sub-assemblages identify here, was also been demonstrate in other studies.…”

“…(8,16) Considering only larger population studies, assemblage A was most frequently identified in Southeastern Brazil, (6,17,18) but assemblage B has been identified as prevalent in other Brazilian regions. (10,19) Interestingly, in the only genotyping study of G. duodenalis in Amazonas/Brazil, conducted in Santa Izabel do Rio Negro, an area inhabited mainly by indigenous peoples, assemblage B was predominant. (9) A similar scenario occurred among indigenous peoples in Mato Grosso, Midwest Brazil, where assemblage B was also predominant.…”

“…(4) The diversity of sub-assemblages identify here, was also been demonstrate in other studies. (10,21,22,23) Likewise, the highest frequency of the AI (BG) sub-assemblage has also been identified in humans in Southeastern Brazil, (17,18) however, worldwide, the sub-assemblage AI(BG) is rare in humans. (24,25,26) The second sub-assemblage most frequent in this study AIII(BG) is also the most prevalent in the indigenous population of Brazilian Amazon.…”

“…(24,25,26) The second sub-assemblage most frequent in this study AIII(BG) is also the most prevalent in the indigenous population of Brazilian Amazon. (9,10) In other Brazilian regions, AIII(BG) is a rare genotype, identified only in Paraná/ South Brazil (n = 1/10, BG). (27) Globally, this genotype was identified in Mozambique/Africa (n = 8/14, BG), (22) Malaysia (n = 6/18, BG) (28) and France (n = 6/14, BG).…”

“…(8) As for the Amazon biome, the prevalence of assemblage B has been noted in two studies conducted in this region based on small indigenous groups. (9,10) To date, there is a gap in terms of animal studies on the occurrence of Giardia in this biome.…”