Assessment of Gastroenteric Viruses in Marketed Bivalve Mollusks in the Tourist Cities of Rio de Janeiro, Brazil, 2022

Abstract

This study investigated the prevalence and genetic diversity of gastroenteric viruses in mussels and oysters in Rio de Janeiro, Brazil. One hundred and thirty-four marketed bivalve samples were obtained between January and December 2022. The viral analysis was performed according to ISO/TS 15216, and the screening revealed the detection of norovirus GII/GI (40.3%), sapovirus (SaV; 12.7%), human mastadenovirus (7.5%), and rotavirus A (RVA; 5.9%). In total, 44.8% (60) of shellfish samples tested positive for one or more viruses, 46.7% (28/60) of the positive samples tested positive for a single viral agent, 26.7% (16) tested positive for two viral agents, 8.3% (5) for three viral agents, and 13.3% (8) for four viral agents. Additionally, three mussel samples were contaminated with the five investigated viruses (5%, 3/60). Norovirus GII showed the highest mean viral load (3.4 × 10⁵ GC/g), followed by SaV (1.4 × 10⁴ GC/g), RVA (1.1 × 10⁴ GC/g), human mastadenovirus (3.9 × 10³ GC/g), and norovirus GI (6.7 × 10² GC/g). Molecular characterization revealed that the recovered norovirus strains belonged to genotypes GII.2, GII.6, GII.9, GII.17, and GII.27; SaV belonged to genotypes GI.1 and GIV.1; RVA to genotypes G6, G8, P[8]-III, and human mastadenovirus to types F40 and F41. The GII.27 norovirus characterized in this study is the only strain of this genotype reported in Brazil. This study highlights the dissemination and diversity of gastroenteric viruses present in commercialized bivalves in a touristic area, indicating the potential risk to human health and the contribution of bivalves in the propagation of emerging pathogens.

Keywords: ISO 15216; bivalve mollusk; food safety; gastroenteric viruses; genotyping; monitoring.

Figure 1

Geographic map of Brazil, highlighting the state of Rio de Janeiro, with the three collected points evaluated in this study: Angra dos Reis (yellow), Niterói (orange), and Rio de Janeiro (red) cities from January to December 2022.

Figure 2

Distribution and percentage of norovirus GI and GII (A), rotavirus A (RVA), human mastadenovirus (HAdV), and sapovirus (SaV) (B) detected in commercial bivalve mollusks collected over a 12-month period—January to December 2022—from three sampling sites: Angra dos Reis, Niterói, and Rio de Janeiro cities, Brazil.

Figure 3

Norovirus (NoV) GII, NoV GI, sapovirus (SaV), human mastadenovirus (HAdV), and rotavirus A (RVA) viral loads in bivalves collected over a 12-month period—January to December 2022—from three sampling sites: Angra dos Reis, Niterói, and Rio de Janeiro cities, Brazil. Box and whisker plots showing all the values distributed within the median (horizontal line in the box) and range concentrations (genome copies per gram (GC/g) of digestive tissue). *** p < 0.001; **** p < 0.0001.

Figure 4

Phylogenetic tree based on the partial capsid (ORF2, VP1 gene) region of norovirus GII. References strains were downloaded from GenBank and labeled with their respective accession numbers. Sequences obtained from bivalve samples (marked with a diamond) in this study from January to December 2022 in Angra dos Reis, Niterói, and Rio de Janeiro cities are shown per country followed by the internal register code number plus the city’s location, year of collection, and genotype (i.e., BRA/LVCA6546_city of Rio de Janeiro/2022/GII.27). Maximum likelihood phylogenetic trees were constructed with MEGA 11 software and bootstrap tests (2000 replicates) based on the Kimura 2-parameter model. The bootstrap percentage values of >70 are shown.

Figure 5

Phylogenetic trees based on (A) the partial VP1 gene of the sapovirus (SaV); (B) the partial VP7 gene of rotavirus A (RVA); (C) the partial VP4 region of (RVA), and (D) the hexon gene of the human mastadenovirus (HAdV). References strains were downloaded from GenBank and labeled with their respective accession numbers. Sequences obtained from bivalve samples (marked with a diamond) in this study from January to December 2022 in Angra dos Reis, Niterói, and Rio de Janeiro cities are shown per country followed by the internal register code number plus the city’s location, and year of collection (i.e., BRA/LVCA6812_city of Rio de Janeiro/2022). Maximum likelihood phylogenetic trees were constructed with MEGA 11 software and bootstrap tests (2000 replicates) based on the Kimura 2-parameter model. The bootstrap percentage values of >70 are shown.

Figure 5

Phylogenetic trees based on (A) the partial VP1 gene of the sapovirus (SaV); (B) the partial VP7 gene of rotavirus A (RVA); (C) the partial VP4 region of (RVA), and (D) the hexon gene of the human mastadenovirus (HAdV). References strains were downloaded from GenBank and labeled with their respective accession numbers. Sequences obtained from bivalve samples (marked with a diamond) in this study from January to December 2022 in Angra dos Reis, Niterói, and Rio de Janeiro cities are shown per country followed by the internal register code number plus the city’s location, and year of collection (i.e., BRA/LVCA6812_city of Rio de Janeiro/2022). Maximum likelihood phylogenetic trees were constructed with MEGA 11 software and bootstrap tests (2000 replicates) based on the Kimura 2-parameter model. The bootstrap percentage values of >70 are shown.