Global market: shellfish imports as a source of reemerging food-borne hepatitis A virus infections in Spain

Shellfish-Associated Enteric Virus Illness: Virus Localization, Disease Outbreaks and Prevention

Numerous outbreaks of shellfish-borne enteric virus illness have been reported worldwide. Most notable among the outbreaks are those caused by NoV and HAV. Lessons learned from outbreak investigations indicate that most outbreaks are preventable. Anthropogenic sources of contamination will continue to invade shellfish growing waters. Shellfish, by their very nature, will continue to bioconcentrate these contaminants, including enteric viruses. There is no quick fix for enteric virus contamination of shellfish; however, vigilance on behalf of the industry, regulatory agencies, and the consumer could substantially reduce the incidence of illness. Enhanced monitoring in all areas of shellfish production, harvesting, distribution, and processing would help to reduce viral illnesses. Pollution abatement and improved hygienic practices on behalf of the industry and consumers are needed. Improved analytical techniques for the detection of enteric viruses in shellfish will lead to enhanced shellfish safety and better protection for the consumer and the industry. Better reporting and epidemiological follow-up of outbreaks are keys to reducing the transmission of foodborne viral infections. It is anticipated that recent advances in analytical techniques, particularly for NoV, will lead to better monitoring capabilities for food and water and a reduction in the incidence of enteric virus illness among shellfish consumers.

Hepatitis A outbreak associated with a revolving sushi bar in Chiba, Japan: Application of molecular epidemiology

AIM

  The number of hepatitis A cases in Japan as well as in other developed countries has been progressively decreasing during the last several years. There is no universal hepatitis A vaccination program in Japan, and a hepatitis A virus (HAV) epidemic in Japan is not unlikely. In 2011, a hepatitis A outbreak associated with a revolving sushi bar occurred in Chiba, Japan. We aimed to analyze this outbreak.

METHODS

  Twenty-seven patients associated with this outbreak were admitted to the National Hospital Organization Chiba Medical Center. Molecular epidemiologic investigations were conducted.

RESULTS

  Twenty-six of the 27 patients had gone to the same revolving sushi bar, and then clinical symptoms appeared. HAV RNA was detected by reverse transcription polymerase chain reaction in 23 of the 27 (85.1%) patients whose sera had tested positive for anti-HAV immunoglobulin M. All isolates from this outbreak were clustered within subgenotype IA, displaying 100% sequence homology with each other in 232 bp from all 23 patients. All isolates belong to the IA-1 sublineage, which is endemic to Japan.

CONCLUSION

  A revolving sushi bar was associated with a hepatitis A outbreak, and molecular epidemiological investigations proved useful.

Changing risk profile of hepatitis A in The Netherlands: a comparison of seroprevalence in 1995-1996 and 2006-2007

The prevalence of antibodies to hepatitis A virus (HAV) was assessed in a nationwide sample (n=6229) in The Netherlands in 2006-2007, and compared to the seroprevalence in a similar study in 1995-1996 (n=7376). The overall seroprevalence increased from 34% in 1995-1996 to 39% in 2006-2007, mainly due to vaccination of travellers and an increased immigrant population. Risk factors remain travelling to, and originating from, endemic regions, and vaccination is targeted currently at these risk groups. Our results show a trend of increasing age of the susceptible population. These people would also benefit from HAV vaccination because they are likely to develop clinically serious symptoms after infection, and are increasingly at risk of exposure through imported viruses through foods or travellers. The cost-effectiveness of adding elderly people born after the Second World War as a target group for prophylactic vaccination to reduce morbidity and mortality after HAV infection should be assessed.

Impaired function of CD4+/CD25+ T regulatory lymphocytes characterizes the self-limited hepatitis A virus infection

BACKGROUND AND AIM

Hepatitis A virus (HAV) causes a transient illness leaving permanent protection against reinfection. Few data are available on the regulatory mechanisms involved in the CD4+ T helper activation. We aimed to investigate the frequency and function of CD3+/CD4+/CD25+ T cells with regulatory function (Tregs) during acute HAV infection.

METHODS

We enrolled 35 consecutive patients and 15 healthy donors, enumerated Tregs by flow cytometry assay and evaluated, after immunomagnetical sorting with magnetic beads, their ability to inhibit the proliferation of CD4+/CD25- T lymphocytes at different ratios (1:1, 1:10, 1:20).

RESULTS

All patients had the usual course of infection. Our immunological analysis showed Tregs frequency in these patients (6.5% [range, 5-8.8%]; 36 [range, 10-87] cells) did not have any statistical difference compared with healthy donors (6% [range, 5-8%]; 48 (range, 23-71) cells), while their ability to suppress CD4+/CD25- was drastically reduced at different ratios (Mann-Whitney U-test; ratio 1:1, 93% vs 72%, z = -3.34, P < 0.0001; ratio 1:10, 86% vs 51%, z = -4.04, P < 0.001; ratio 1:20, 56% vs 30%, z = -3.43, P < 0.0001). After the seroconversion, CD4+/CD25+ frequency and function in HAV-infected patients did not differ from healthy individuals.

CONCLUSION

CD4+/CD25+ T cells seem to be impaired in their function during the HAV acute infection. This evidence might help to determine an optimal T helper cell immune network that is a predisposing factor for a self-limiting disease.

Detection of hepatitis A virus (HAV) in oysters (Crassostrea gigas)

Because shellfish (oysters, clams, and mussels) are filter-feeders, pathogens become concentrated within them, and human consumption of raw, or under-cooked shellfish can result in disease outbreaks. Identification of hepatitis A virus (HAV) in shellfish has been difficult for several reasons: the concentration of virions in shellfish tissues are very low, detection methods based on in vitro propagation are unreliable, recovery of virions from shellfish tissues is inefficient, and PCR inhibitors in shellfish tissues limit the success of RT-PCR. These facts underlie difficulties in determining cause and effect relationships between hepatitis A outbreaks and detection of HAV contamination in shellfish samples. We have developed a reliable and highly sensitive method for detection of HAV in oyster tissues at low levels (0.001 FFU/ml-fluorescent focus units per milliliter). Our method combines dissection of the gastrointestinal oyster tract, organic extraction before PEG precipitation, and RNA extraction with Trizol LS, followed by RT-PCR and hybridization using a digoxigenin-labeled HAV cDNA probe. Our results will benefit both public health officials concerned about hepatitis A infections caused by consumption of HAV-contaminated oysters and shellfish producers who require reliable methods for quality control of commercial oyster production.

Clusters of autochthonous hepatitis A cases in a low endemicity area

At the University Hospital of Besançon (département of Doubs, France), an unusually high number of patients were hospitalized for hepatitis A during the 1999-2000 period, some of whom had not travelled abroad. This prompted us to conduct an investigation on a population basis and search for clusters of cases possibly related to local sources of contamination. Accordingly, case definition was restricted to autochthonous cases. During the 1999-2002 period, 45 autochthonous cases were classified as possibly originating from local environmental sources. A space-time scan statistic detected one most likely cluster (standardized incidence ratio 20.63, 95% confidence interval 10.6-37.1), consisting of 11 persons (of whom five children had attended the same swimming pool). It remained significant in a sensitivity analysis, strongly supporting the hypothesis of an environmental source of contamination. This study reveals the necessity of regular surveillance for hepatitis A and raises the issue of virological surveys of pool waters.

Pressure inactivation of hepatitis A virus in strawberry puree and sliced green onions

Hepatitis A can be acquired by ingesting contaminated produce. To investigate the potential of high-pressure processing as an intervention strategy for virus in produce, strawberry puree and sliced green onions were inoculated with > 10(6) PFU of hepatitis A virus and treated with pressures ranging from 225 to 375 megapascals (MPa) in 25-MPa increments at ambient temperature. Subsequent virus extraction and plaque assay determined that hepatitis A virus was inactivated in strawberry puree and sliced green onions after 5-min exposures to pressures of 375 MPa with log PFU reductions of 4.32 and 4.75, respectively. Hepatitis A virus was equally sensitive in puree and onions at pressures > or = 350 MPa. For treatments of < 325 MPa, the virus was more sensitive to pressure in strawberry puree than in sliced onions with log reductions of 1.2, 2.06, and 3.13 observed for strawberries and 0.28, 0.72, and 1.42 observed for onions after 5-min treatments at 250, 275, and 300 MPa, respectively. Although high-pressure processing may cause some organoleptic alterations to strawberries and onions, results show high-pressure processing will inactivate hepatitis A virus in these foods.

Determinants of acquiring hepatitis A virus disease in a large Italian region in endemic and epidemic periods

Viral hepatitis A is endemic in Puglia region (southeast Italy). Over the last 13 years, annual incidence rates have ranged from 4 to 138 per 100,000 inhabitants and periodical regional epidemics have been described. Between 1 January 1996 and 31 December 1997 over 11,000 cases of hepatitis A were reported accounting for an annual incidence rate over 130/100,000. To identify exposures during the epidemics, a case-control study was performed in two different rounds and since 1997, an enhanced surveillance system has permitted the monitoring of exposures of subsequent cases. Raw seafood consumption was identified as the major risk factor for hepatitis A. Adjusted odds ratio and 95% confidence intervals for this exposure from the first round of the case-control study was 38.6 (12.2-122.4) and for the second round for consumption of raw mussels it was 30.7 (16.0-52.0). Hepatitis A epidemiology in Puglia is consistent with an endemic situation sustained by locally contaminated seafood consumed raw and by the recurrence of large epidemics, where size is influenced by the accumulation of susceptible subjects in the population.

High-pressure inactivation of hepatitis A virus within oysters

Previous results demonstrated that hepatitis A virus (HAV) could be inactivated by high hydrostatic pressure (HHP) (D. H. Kingsley, D. Hoover, E. Papafragkou, and G. P. Richards, J. Food Prot. 65:1605-1609, 2002); however, direct evaluation of HAV inactivation within contaminated oysters was not performed. In this study, we report confirmation that HAV within contaminated shellfish is inactivated by HHP. Shellfish were initially contaminated with HAV by using a flowthrough system. PFU reductions of >1, >2, and >3 log(10) were observed for 1-min treatments at 350, 375, and 400 megapascals, respectively, within a temperature range of 8.7 to 10.3 degrees C. Bioconcentration of nearly 6 log(10) PFU of HAV per oyster was achieved under simulated natural conditions. These results suggest that HHP treatment of raw shellfish will be a viable strategy for the reduction of infectious HAV.