Environmental surveillance of norovirus and hepatitis A virus in raw oysters at seafood retails in Sinaloa, Mexico: detection of GII.P13 norovirus genotype

Abstract

Background Norovirus (NoV) and hepatitis A virus (HAV) have emerged as the leading agents of non-bacterial acute gastroenteritis and hepatitis, respectively, primarily associated to food-borne outbreaks followed by the consumption of seafood. In Mexico, little is known about the molecular epidemiology of NoV and HAV, and a few studies have reported their presence in aquatic environments. In Sinaloa, the pleasure oyster (Crassostrea cortiziensis, Hertlein) is one of the main species consumed at seafood retails; however, information about the presence and genetic diversity of NoV and HAV is lacking. The aim of the present study was to investigate the prevalence and molecular diversity of NoV and HAV in raw pleasure oysters expended at seafood retails in Sinaloa, Mexico. Methods A total of 68 samples were collected at several seafood retails at four periods: Period 1 (October-November, 2010); Period 2 (December 2010-January 2011); Period 3 (March-April, 2011); and Period 4 (May, 2011). These oyster samples were tested for the presence of NoV and HAV by retrotranscription (RT)-nested PCR and RT-PCR, respectively. Enumeration of fecal coliforms was also conducted. In addition, an analysis of Binary Logistic Regression (BLR) was performed to determine a possible correlation of these enteric viruses with the presence of fecal coliforms and environmental temperature. Results Overall, NoV was detected in 57.3% of the 68 samples showing the highest occurrence (11/13) during Period 1 (October-November, 2010). No HAV-positive samples were detected. Fecal coliforms were more frequently detected (16/20) on Period 4 (May, 2011). A significant negative correlation between NoV and fecal coliforms was observed. A total of 28 sequences were obtained from NoV amplicons and surprisingly, phylogenetic analysis showed that all NoV sequences obtained from oysters belonged to GII.P13 genotype. Conclusions The results indicated that raw oysters expended at seafood retails are potential sources of human infection due to the presence of NoV, which interestingly were represented only by GII.P13 genotype. This is the first report confirming the presence of GII.P13 in Mexico, which may contribute with the better understanding of NoV genetic diversity and epidemiology.