Epidemiology Update of Hepatitis E Virus (HEV) in Uruguay: Subtyping, Environmental Surveillance and Zoonotic Transmission

Abstract

Hepatitis E Virus (HEV) infection is an emergent zoonotic disease of increasing concern in developed regions. HEV genotype 3 (HEV-3) is mainly transmitted through consumption of contaminated food in high-income countries and is classified into at least 13 subtypes (3a-3n), based on p-distance values from complete genomes. In Latin America, HEV epidemiology studies are very scant. Our group has previously detected HEV3 in clinical cases, swine, wild boars, captive white-collared peccaries, and spotted deer from Uruguay. Herein, we aimed to provide novel insights and an updated overview of the molecular epidemiology of zoonotic HEV in Uruguay, including data from wastewater-based surveillance studies. A thorough analysis of HEV whole genomes and partial ORF2 sequences from Uruguayan human and domestic pig strains showed that they formed a separate monophyletic cluster with high nucleotide identity and exhibited p-distance values over the established cut-off (0.093) compared with reference subtypes' sequences. Furthermore, we found an overall prevalence of 10.87% (10/92) in wastewater, where two samples revealed a close relationship with humans, and animal reservoirs/hosts isolates from Uruguay. In conclusion, a single, new HEV-3 subtype currently circulates in different epidemiological settings in Uruguay, and we propose its designation as 3o along with its reference sequence.

Keywords: Hepatitis E virus; Uruguay; molecular epidemiology; subtype 3o; wastewater.

Figure 1

Water sampling from different cities throughout Uruguay. Wastewater samples were analyzed from the cities indicated with a black full circle. Surface water samples were analyzed from the places indicated with a red full circle. The number of samples studied is shown in brackets for each location. Population density (People/Sq Km) per department is indicated in the map, based on the values extracted from Anuario Estadistico Nacional 2019, 96^a version, Instituto Nacional de Estadística (INE), www.ine.gub.uy (accessed on 12 June 2023). The map of Uruguay was obtained from the USGS National Map Viewer (http://viewer.nationalmap.gov/viewer/, accessed on 12 June 2023).

Figure 2

Phylogenetic reconstruction of HEV complete genomes for genotype 3. The tree was generated with the Neighbor-Joining algorithm using the Tamura-Nei parameters method employing Molecular Evolutionary Genetics Analysis (MEGA) v7 software. The robustness of the tree was determined via bootstrap analysis for 1000 replicates. Only values ≥60% are shown. Reference sequences for the subtypes 3a–3n and unclassified isolates are included. The putative new 3o subtype proposed for Uruguayan (MW598896 and MZ969073) and Brazilian sequences (OQ433914 and OQ433915) is shown and the proposed reference strain for this subtype (MW596896) is indicated with a black full circle.

Figure 3

Phylogenetic tree based on a 719 bp fragment within ORF2. Tree reconstruction was performed using the Neighbor-Joining method with the Tamura-Nei model using Molecular Evolutionary Genetics Analysis (MEGA) v7 software. The robustness of the tree was determined via bootstrap analysis for 1000 replicates. Only values of ≥60% are shown. Reference sequences for the subtypes 3a–3n and unclassified strains are included. The HEV-3 wastewater sequences (HE-67-WW and HE-112-WW) and the swine complete genome HEV-8_uy (MZ969073) reported in this study are indicated with a black triangle. Proposed reference sequence for the novel 3o subtype is indicated with a black circle.