Risk Assessment in Shellfish-Borne Outbreaks of Hepatitis A

Abstract

In the present work, we aimed at determining the relationship between the hepatitis A virus (HAV) numbers in imported frozen coquina clams involved in two hepatitis outbreaks, as well as the risk for human health. Due to HAV unculturability, a standardized TaqMan real-time reverse transcription-PCR controlling the virus/ nucleic acid extraction and enzyme efficiencies was employed to figure the exposure dose for clams responsible for hepatitis cases. HAV numbers were then employed to figure the risk of infection based on a dose-response model for echovirus 12. The estimated risk of infection after consumption of lightly cooked clams matched actual attack rates. Our data show that prospective monitoring of bivalve samples may fail to prevent the occurrence of outbreaks, since HAV was detected in 44% of samples directly associated with cases but was undetectable in samples that were randomly collected from the importers and belonged to the same batches. A correlation was nevertheless observed between the prevalence of hepatitis A cases in the harvesting areas and positive HAV isolation in clams, which points to the need to identify and prevent hazards rather than relying on random sampling of finished products to ensure safety. However, when evidence shows that a critical limit of viral contamination has been exceeded in the potential sources of contamination discharging into the shellfish-growing beds, quantitative virological analysis addressing quality assurance and quality control requirements should be performed with the bivalves. This work provides the first evidence of accurate HAV levels in shellfish involved in outbreaks that could be of use for risk assessment purposes.

Food safety issues in fresh produce: Bacterial pathogens, viruses and pesticide residues indicated as major concerns by stakeholders in the fresh produce chain

“…By the scientists, product control was not considered as an important control measure, suggesting that they are familiar with the limitations related to sampling and product analysis from a statistical point of view, in particular for microbial hazards (Pinto, Costafreda, I, & Bosch, 2009;Jongenburger, Reij, Boer, Gorris, & Zwietering, 2011). Other stakeholders such as the competent authorities were convinced that because of growing international trade, border controls of product will become increasingly important as an additional measure to assure food safety.…”

Analytical Methods for Virus Detection in Water and Food

“…Data on shellfish is still scarce, but some publications reported NoV concentrations ranging from 10 2 to 10 4 copies per gram of digestive tissues (Nishida et al 2007;Le Guyader et al 2003. HAV has recently been quantified in naturally contaminated shellfish samples, showing titers ranging from 10 3 to 10 5 HAV genomes per gram of clam (Costafreda et al 2006;Pintó et al 2009), and it has also been reported in titers of 0.2-224 infectious particles per 100 g shellfish meat (Williams and Fout 1992). Therefore, the methods for detection of viruses on food samples must have a high level of analytical sensitivity and specificity.…”

“…Recently, the use of a nonpathogenic viruses, mengovirus MC0 (Mattison et al 2009) and feline calicivirus (Butot et al 2008;Cannon et al 2006;Hewitt and Greening 2004;Pintó et al 2009), have been proposed as process control, although the latter has been reported to be an inappropriate surrogate for NoV in acid conditions (Pintó et al 2009). Quantitative standardized procedures presently enable to perform quantitative microbial risk assessment (QMRA) in food samples (Gassilloud et al 2003;Arnal et al 1998).…”

Scientific Opinion on the minimum hygiene criteria to be applied to clean seawater and on the public health risks and hygiene criteria for bottled seawater intended for domestic use

“…Survival/growth in ice, fishery products and seawater HAV is a highly stable virus, able to persist for extended times in the environment (Abad et al, 1994a;Abad et al, 1994b;Sobsey et al, 1988) and its transmission by contaminated foods and drinking water has been demonstrated (Bosch et al, 1991;Dentinger et al, 2001;Pinto et al, 2009;Reid and Robinson, 1987;Rosemblum et al, 1990;Sanchez et al, 2002), although most cases seem to occur through person-to-person transmission. Foods of primary importance are those susceptible to be contaminated at the pre-harvest stage such as bivalve molluscs, particularly oysters, clams and mussels, salad crops, such as lettuce, green onions and other green leafy vegetables, and soft fruit, such as raspberries and strawberries.…”