Category Archives: Vibrio parahaemolyticus

Research – Raw Aquatic Food Products – A Source of Pathogens and Parasites


The harmful microorganisms of concern include both bacteria (e.g. Vibrio parahaemolyticus (VP) and Vibrio cholerae (VC)) and viruses (e.g. norovirus). VP occurs naturally in seawater (estuaries and coastal areas). Hence, some seafood is inevitably contaminated with VP. On the other hand, VC can live in both saltwater and freshwater such as rivers. In Hong Kong, norovirus is a prevalent foodborne virus that is commonly found in polluted seawater and shellfish living in polluted areas is easily contaminated.

Research – Advances in science and risk assessment tools for Vibrio parahaemolyticus and V. vulnificus associated with seafood: meeting report


Globally, the Vibrio parahaemolyticus and Vibrio vulnificus represent important human pathogens associated with the consumption of seafood. In response to the requests for scientific advice from Codex Committee on Food Hygiene (CCFH), risk assessments for the pathogens V. vulnificus, V. cholerae, V. parahaemolyticus and guidance on methods for the detection of Vibrio spp. with seafood have been conducted and published previously by JEMRA. In order to provide an update on the state-of-the-art advice regarding risk assessment for V. parahaemolyticus and V. vulnificus in seafood, an expert meeting was convened.

Several critical developments in the last decade were subsequently noted by the expert working group: 1) The emergence of highly pathogenic strains; 2) In response to climate change, there has been a significant geographical spread regarding when and where these seafood-associated Vibrio infections; 3) Demographic considerations are very important; 4) A range of new approaches for best practice; and 5) A range of new methods, such as those utilising genomics and satellite imagery. This report describes the output of that expert meeting.

RASFF Alert – Vibrio parahaemolyticus – Mussels


Vibrio parahaemolyticus in mussels (mytilus galloprovincialis) produced in Italy and reared in Spain in Italy

New Zealand – Collecting shellfish this summer? Cook it to keep your whānau safe from Vibrio


New Zealand Food Safety is calling on Kiwis to thoroughly cook the shellfish they collect this summer following an increase in cases of Vibrio parahaemolyticus illness in previous summer months.

Vibrio is a type of bacteria naturally living in the sea, and some strains can make people sick with gastroenteritis when consumed in raw or undercooked shellfish.

“Our message to those who want to eat raw or lightly cooked shellfish – like mussels, kina and pipi – is to be aware there are increased risks of illness and the simple precautions you can take to protect yourselves and your families,” says New Zealand Food Safety deputy director-general Vincent Arbuckle.

“We are starting to see more cases of illness from Vibrio parahaemolyticus. While we can’t definitively identify the cause, it is possibly because of rising sea temperatures, making it easier for bacteria to spread.

“So, as we gear up for summer, and enjoy time with family and friends over the holidays, we need to make sure to take extra care when collecting and preparing shellfish.

“In the most recent outbreak, there were 60 reported cases of Vibrio parahaemolyticus, between November 2021 and May 2022. Of particularly of concern is the high hospitalisation rate of almost 42%.

“It’s a notable increase in reported cases from previous years, with 24 cases reported earlier in 2021, 16 cases in 2020 and 23 cases in 2019. The reason for the increase is unclear at this stage – it could be caused by environmental change, increased testing and reporting, or a combination of these and other factors – but it is clear, that cooking your shellfish kills the bacteria that makes you sick.

Vibrio bacteria can cause illnesses like gastroenteritis – with symptoms including diarrhoea, abdominal cramps, nausea, vomiting and fever – blood poisoning and wound infections.

“It’s especially important for those with underlying health conditions, pregnant and older people, and younger children to avoid eating raw shellfish,” Mr Arbuckle said.

“The more people know how to collect, store, prepare and cook shellfish safely, the more they can look out for both themselves and others in our communities who may be more vulnerable.

“We want people to know there are easy, tasty ways to make the kai moana you collect safe for eating, so we’ve released a series of simple recipes, created by a community chef. These are available on the website to download and enjoy.

“On our own, we can’t control the changing environmental factors, but we can all help look after our whānau and reduce the risk of them falling sick from Vibrio by taking some simple precautions – and by spreading the word on safe ways to cook shellfish.”

What you can do to help keep your whānau safe:

  • Don’t eat shellfish raw or undercooked. Cook shellfish thoroughly (until they open and are firm to the touch) or so they get to at least 65°C for 1 minute. 
  • Avoid gathering shellfish after heavy rainfall or if the water is unusually dirty.
  • Keep shellfish alive and cool.
  • Refrigerate your shellfish as soon as possible and, ideally, eat it on the day of collection or within 2 days.
  • To avoid cross-contamination, keep hands and utensils clean to prepare raw shellfish, and keep raw shellfish separated from cooked or ready-to-eat products.

What to do if someone falls sick after eating shellfish:

  • phone healthline on 0800 61 11 16, or
  • seek medical attention immediately.

If possible, store and refrigerate any leftover shellfish for testing.

More information on Vibrio and shellfish food safety tips

Research – Antibiofilm Efficacy of Quercetin against Vibrio parahaemolyticus Biofilm on Food-Contact Surfaces in the Food Industry


Vibrio parahaemolyticus, one of the most common foodborne pathogenic bacteria that forms biofilms, is a persistent source of concern for the food industry. The food production chain employs a variety of methods to control biofilms, although none are completely successful. This study aims to evaluate the effectiveness of quercetin as a food additive in reducing V. parahaemolyticus biofilm formation on stainless-steel coupons (SS) and hand gloves (HG) as well as testing its antimicrobial activities. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin at sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. Control group was not added with quercetin. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of target genes linked to flagellar motility (flaAflgL), biofilm formation (vp0952vp0962), virulence (VopQvp0450), and quorum-sensing (aphAluxS) were all dramatically suppressed. Quercetin (0–110 μg/mL) was investigated on SS and HG surfaces, the inhibitory effect were 0.10–2.17 and 0.26–2.31 log CFU/cm2, respectively (p < 0.05). Field emission scanning electron microscopy (FE-SEM) corroborated the findings because quercetin prevented the development of biofilms by severing cell-to-cell contacts and inducing cell lysis, which resulted in the loss of normal cell shape. Additionally, there was a significant difference between the treated and control groups in terms of motility (swimming and swarming). According to our research, quercetin produced from plants should be employed as an antibiofilm agent in the food sector to prevent the growth of V. parahaemolyticus biofilms. These results indicate that throughout the entire food production chain, bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood industry. View Full-Text

Europe – ECDC Vibrio Map Viewer


ECDC Vibrio map viewer


The Vibrio suitability tool (Vibrio map viewer) shows the environmental suitability for Vibrio growth in the Baltic Sea. It is a near real-time model that uses daily updated remote sensing data to examine worldwide environmental conditions, such as sea surface temperature and salinity for Vibrio spp.. The model used for the Vibrio viewer has been calibrated to the Baltic Region in Northern Europe and might not apply to other worldwide settings prior to validation.

Infections caused by Vibrio species other than V. cholerae can be serious, particularly for immunocompromised persons. However, the overall occurrence is low despite an increase having recently been observed in northern Europe.

ECDC monitors Vibrio growth in the Baltic Sea during the summer. If and when the risk of Vibrio growth is determined as medium or above, notifications are reported in the weekly threats reports (CDTR). The original viewer is available on the ECDC website:

RASFF Alert- Vibrio cholerae, parahaemolyticus, vulnificus – Shrimp


Detection of vibrio in shrimp from Venezuela in France


Vibrio cholerae, vibrio parahaemolyticus and vibrio vulnificus detected in frozen shrimps from Vietnam in France

Hong Kong – Pre-shucked Oysters for Raw Consumption – What Should One be Aware of?


french oysters

Raw Oysters are High-risk Foods
Oysters are filter feeders. They constantly draw in water and accumulate materials from water, including pathogens such as Vibrio bacteria, norovirus and hepatitis A virus. These pathogens can infect people who eat oysters raw or undercooked. In addition, bacteria like Vibrio can continue to grow in oysters after harvesting if oysters are not maintained at low enough temperatures from harvest through to consumption. Food poisoning outbreaks related to raw oysters have been reported locally from time to time. Although the illness is usually mild and self-limiting, causing symptoms such as diarrhoea, abdominal cramps and vomiting, they can also cause severe health consequences especially for susceptible individuals.

Additional Risks in Shucked Oysters
Both physical and microbiological contamination are possible during the shucking of oysters. Physical removal of shellfish meat from the shell at the shucking table often exposes the product to dirt, mud and detritus. Shucked oysters should be rinsed or washed well to eliminate these contaminants and to reduce microbiological level of the products. Good hygiene practices should also be observed to minimise contamination from the workers and the working environment.

Before deshelling, oysters can stay alive even after long-haul shipping if kept under correct temperature and conditions. Once killed after shucking, raw oysters can deteriorate quickly if the temperature is not low enough to limit bacterial growth. Shucked oysters should be packed and chilled or frozen as soon as possible. Furthermore, an uninterrupted cold chain during transportation is critical to ensure safety and quality of the shellfish products.

Research – Prevalence, genomic characterization, and risk assessment of human pathogenic Vibrio species in seafood

Journal of Food Protection

Pathogenic Vibrio spp. are largely responsible for human diseases caused through consumption of contaminated seafood. The aim of this study was to determine the prevalence, population densities, species diversity and molecular characteristics of pathogenic Vibrio in various seafood commodities and its associated health risks. Samples of finfish and shellfish (oysters and sea urchins) were collected from different regions and analyzed for Vibrio using the Most Probable Number (MPN) technique. Genomic DNA of putative Vibrio isolates was analyzed by whole genome sequencing (WGS) for taxonomic identification and identification of genes responsible for virulence and antimicrobial resistance. The risk of vibrio-related illnesses due to the consumption of contaminated seafood was assessed using Risk Ranger. Population densities of presumptive Vibrio fell in the range of 2.6 – 4.4 Log MPN/g and correlated with seasonality, with the summer season favoring significantly (p < 0.05) higher Vibrio counts. A total of 15 Vibrio isolates were identified as V. alginolyticus (5), V . parahaemolyticus (6), V. harveyi (2) or V. diabolicus (2). Two of the six V. parahaemolyticus isolates (ST 2504 and ST 2505) originating from oysters were found to be either tdh + or trh + and thus considered a human pathogen due to elaboration of Thermostable Direct Hemolysin (TDH) or TDH-related hemolysin (TRH). In addition to virulence genes, the shellfish isolates also harbored genes encoding resistance to multiple antibiotics including tetracycline, penicillin, quinolone and beta-lactam antibiotics, thus arousing concern. The risk assessment exercise pointed to an estimated 21 annual cases of V. parahaemolyticus -associated gastroenteritis in the general population attributed to consumption of contaminated oysters. This study highlights not only the wide prevalence and diversity of Vibrio in seafood, but also the potential of certain strains to threaten public health.

Research – Epidemiological and microbiological investigation of a large increase in vibriosis, northern Europe, 2018


Food Illness

The habitat of  spp. bacteria is fresh and brackish water with moderate salinity. Non-toxigenic , as well as several human pathogenic non-cholera  species, including  and , cause vibriosis after seawater exposure or consumption of contaminated seafood [1]. Clinical manifestations range from mild gastroenteritis and otitis to wound infections that may lead to severe necrotising fasciitis and septicaemia with a potentially fatal outcome [25].

The Baltic Sea region is one of the areas where increasing numbers of cases related to  species causing vibriosis (VCV) have been reported in the last decades [6]. Several studies have shown how the occurrence of heatwaves, which lead to an increase in sea surface temperature, are linked with an increase in the number of reported vibriosis cases [4,712]. For instance, the years with an especially warm summer in the Baltic Sea region, 2006, 2010 and particularly 2014 (the warmest year in historical records at the time), were also the years with the largest number of vibriosis cases reported [6,11].

However, there is a notable gap in surveillance data for vibriosis since it is not a notifiable disease in the majority of European countries [1,6]. Therefore, the aim of this multi-country study was to describe the epidemiology of vibriosis cases in countries bordering the North and Baltic Seas area during the exceptionally warm year of 2018 [13,14], in order to investigate the extent of these infections in the study countries, map their genetic diversity, understand the predictors for developing severe vibriosis, and propose recommendations for public health measures.