First investigation of Ostreid herpesvirus-1 and human enteric viruses in a major scallop production area in Brazil

Bivalve mollusks may be affected by numerous infectious diseases, which cause high mortality rates and economic burdens for producers. Another challenge for bivalve aquaculture is the protection of farms from human contamination, such as sewage and stormwater discharges. Ilha Grande Bay (IGB), located in Rio de Janeiro state, is the largest Brazilian producer of scallops (Nodipecten nodosus). This region has recently suffered a mass mortality of mollusks, and several environmental contaminants have been reported in the area. To contribute to the elucidation of scallop collapse and better characterize the human impacts, this study assessed the circulation of mollusk (Ostreid herpesvirus-1 [OsHV-1]) and human (mastadenovirus [HAdV] and norovirus GII) viral pathogens in waters and animals produced at IGB. Neither water nor animals were positive for OsHV-1. However, of the 7 points analyzed, 5 points showed contamination by HAdV or norovirus. HAdV and norovirus were detected in 5.5 and 6.9% of the analyzed water samples, respectively, in concentrations ranging from 2.39 × 10³ to 1 × 10⁵ genome copies/L. One scallop sample was positive for norovirus (4.5%). These results demonstrate human contamination in the region, presenting a risk of consumer contamination, and a non-association between OsHV-1 and the mass mortality described in scallops.