Molecular epidemiology of Giardia spp. in northern Vietnam: Potential transmission between animals and humans

Hanako Iwashita,Tetsuhiro Sugamoto,Taichiro Takemura,Asako Tokizawa,Thiem Dinh Vu,Tuan Hai Nguyen,Tho Duc Pham,Na Ly Tran,Hang Thi Doan,Anh Hong Quynh Pham,Tetsu Yamashiro

doi:10.1016/j.parepi.2020.e00193

Abstract

Giardia spp. is detected frequently in humans and animals. Although many studies have been conducted on the epidemiology of giardiasis, there is a scarcity of information on the genetic diversity and the dynamics of transmission of Giardia spp. in Vietnam. The zoonotic potential of Giardia spp. remains elusive. The objective of this study was to determine the genetic diversity of Giardia spp. in both humans and livestock to assess the existence of a route of infection between livestock and humans. Our goal was to assess the role animals play in the epidemiology of human infection in northern Vietnam. In Hien Khanh commune in northern Vietnam, 311 households with 1508 residents were randomly selected for a diarrheal cohort study. Of these, 2120 human diarrheal samples were collected from 1508 residents in 2014 and 2017. Of these, non-diarrheal samples were cross-sectionally collected from 471 residents. At the same site, livestock samples from buffalo, dairy and beef cattle, pigs, and dogs were collected. All stool samples were examined for Giardia spp. by Direct Immunofluorescence Assay (DFA) using fluorescent microscope. DNA extraction, PCR analysis of the 3 genes (bg, gdh, tpi), and sequencing analysis were continuously carried out. A total of 23 animal stool samples, 8 human non-diarrheal samples, and 36 human diarrheal samples were Giardia spp. were positive by PCR using the bg and gdh genes. Giardia spp. assemblage AII and E were detected in both animal samples and human samples in this study site. The detection of assemblage E in human stool samples suggests the first human case report in Vietnam. We assume that the unexpected human infection of all Giardia assemblages including A, B, and E may be due to an environment contaminated with animal and human feces in this village.

Highlights

Giardia spp.is the etiologic agent of giardiasis in humans and other animals throughout the world (Ryan and Cacciò, 2013)
Assemblage A was categorized in 2 sub-assemblages; one is sub-assemblage AII, which is commonly found in humans (Avendaño et al, 2019; Faria et al, 2017; Hernández et al, 2019; Lecová et al, 2018; Naguib et al, 2018), it has been reported in a number of studies in animals; and the other sub-assemblage AIII is mainly found in animals (Feng and Xiao, 2011; Ryan and Cacciò, 2013; Thompson and Ash, 2016)
Our research revealed that the novel genotype belonging to assemblage AIII has been isolated only in buffalo and assemblage B appeared only in humans

Summary

Introduction

Giardia spp.is the etiologic agent of giardiasis in humans and other animals throughout the world (Ryan and Cacciò, 2013). Previous epidemiological studies have shown that Giardia spp. is common in livestock worldwide. In central Vietnam, Nguyen et al detected Giardia spp. in cattle in small-scale farms (Nguyen et al, 2016). Researchers considered cattle, pre-weaned calves, to be a major contributor to zoonotic infections (Abeywardena et al, 2012; Santín et al, 2009). In Vietnam, the raising of livestock including cattle and other animals is a traditional agricultural practice (Nguyen et al, 2016). The zoonotic transmission potential of Giardia spp. remains a major and unresolved issue

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