Detection of noroviruses in shellfish in the Netherlands

Abstract

Shellfish from oyster farms in the Netherlands and imported from other European countries were examined for viral contamination. A method that allows sequence matching between noroviruses from human cases and shellfish was used. The samples of shellfish (n = 42) were analyzed using a semi-nested RT-PCR that had been optimized for detection of norovirus in shellfish (SR primer sets). In addition, a different genome region was targeted using a second primer set which is routinely used for diagnosis of norovirus infection in humans (JV12Y/JV13I). To improve the detection limit for this RT-PCR a semi-nested test format was developed (NV primer sets). One of 21 oyster samples (4.8%) from Dutch farms was norovirus positive, whereas norovirus was detected in 1 out of 8 oyster samples (12.5%) and 5 out of 13 mussel samples (38.5%) collected directly after importation in the Netherlands. RNA from samples associated with an outbreak of gastro-enteritis in the Netherlands in 2001 was re-analyzed using the NV primer sets. At least one identical sequence (142/142 nt) was found in three fecal and in two oyster samples related to this outbreak. Further surveillance of norovirus by detection and typing of viruses from patients with gastroenteritis and shellfish is warranted to clarify the causes of future outbreaks.

Aichi Virus, Norovirus, Astrovirus, Enterovirus, and Rotavirus Involved in Clinical Cases from a French Oyster-Related Gastroenteritis Outbreak

“…More oyster samples were found to be contaminated with GII NoVs than GI strains in the first week after the contamination event, but after 4 weeks, a greater percentage of samples contained GI NoV strains. Previous studies have shown that GI NoVs are more resistant to sewage treatment (8) and are more often implicated in foodrelated outbreaks than are GII NoV strains (5,11,15,19). The findings in the present study support the hypothesis that GI NoVs are more stable in the environment and may explain the relatively higher frequency with which strains from this genogroup are associated with food-borne outbreaks.…”

“…Food contamination by sewage has often been suspected when multiple strains are detected in food or in patient stool samples, as previously reported with shellfish (4,5,15,18,19). Only noroviruses were detected or reported in prior re- (15) reported that the majority of mixed norovirus infections were associated with shellfish consumption.…”

Detection of Multiple Noroviruses Associated with an International Gastroenteritis Outbreak Linked to Oyster Consumption

“…During the 2 to 3 days of clinical disease (and probably longer after the disappearance of symptoms), viruses replicate in the intestine, which results in watery diarrhea and the shedding of a large quantity of progeny viruses (14). This, together with the very low infectious dose of NoVs and their high resistance in the environment, explains why more than half of food-borne NoV outbreaks have been associated with food requiring handling but no subsequent heating, with water, or with foods such as raspberries or shellfish (6,15,17,19,20,26). In this respect, shellfish are a unique food since they filter large volumes of water for feeding, they grow in coastal areas that may be contaminated by sewage, and they are usually consumed uncooked (8,18,31).…”

“…In this respect, shellfish are a unique food since they filter large volumes of water for feeding, they grow in coastal areas that may be contaminated by sewage, and they are usually consumed uncooked (8,18,31). Therefore, in countries where raw oysters represent a traditional food, a number of food-borne outbreaks of NoV gastroenteritis have been reported (6,12,15,19). However, it is sometimes a challenge in multiplestrain outbreaks to link cases to the consumption of the food (6,15,20).…”

Real-time PCR quantitative assessment of hepatitis A virus, rotaviruses and enteroviruses in the Tyume River located in the Eastern Cape Province, South Africa

“…NoV genogroup GI and GII specific primer sets which target the viral RNA-dependent RNA polymerase gene (Boxman et al, 2006) were used. These primer sets have been used in previous studies for detecting NoV GI and GII in environmental samples (Victoria et al, 2010).…”