Liz Bradshaw | Food Safety News

Seafood Safety 101: Vibrio in Shellfish

Liz Bradshaw — Wed, 08 Apr 2015 05:02:05 +0000

(This article by Liz Bradshaw, a postdoctoral research scholar in NoroCORE, the Norovirus Collaborative for Outreach, Research, and Education based at NC State, is the fifth in a series leading up to April 7, when the World Health Organization celebrated World Health Day, focusing this year on food safety. The first article in the series can be found here, the second one is here, the third is here, and the fourth is here.) People around the world are eating more and more seafood, and if you’re from the southeastern United States, oysters and other shellfish are a desirable delicacy for many. Most people are aware that eating raw or undercooked seafood can put them at risk for food-related illness, and while they have seen the warnings on restaurant menus, but may not know the specific microbes to blame. This post focuses on what is arguably the most important pathogen found in seafood (which is also on the rise) – Vibrio bacteria. Vibrio refers to a genus of Gram-negative, rod-shaped bacteria, and they are found naturally in brackish and saltwater environments since they need salt to survive and grow. They also like to multiply in warm water, and the majority of human cases happen in the summer months. Of around a dozen Vibrio species that cause disease in people, two species — V. parahaemolyticus and V. vulnificus — are most often associated with eating raw or undercooked seafood, particularly molluscan shellfish (oysters, clams, mussels, and cockles). These bacteria can also enter through a wound or by ingesting seawater, but these cases are less common. V. parahaemolyticus usually causes watery diarrhea, vomiting, and abdominal pain, sometimes with a fever and chills. People are usually sick for three days, and though unpleasant, the majority of people recover just fine, without needing prescription medications. The Centers for Disease Control and Prevention (CDC) estimates there are 35,000 V. parahaemolyticus cases a year in the U.S. V. vulnificus is a rarer but more sinister creature and is often associated with fatalities. Most people with V. vulnificus experience symptoms similar to V. parahaemolyticus, but the bacteria are a particular threat to those who are immunocompromised or have underlying health conditions such as liver disease, diabetes, or cancer. In these patients, the bacteria can enter the bloodstream (septicemia), causing severe fever, skin lesions, and shock. Around 50 percent of these patients die, and that is often in the face of aggressive antibiotic treatment and supportive care, which is more than a little scary. V. vulnificus infection is, however, a rare disease; there are only about 30 cases a year in the U.S. The incubation periods (the time between eating the contaminated shellfish and becoming sick) are quite different for the two bacteria. V. parahaemolyticus starts making itself known around two to 48 hours after exposure, while V. vulnificus takes one to seven days. A clinical diagnosis using bacterial culture is still needed to be sure Vibrio is the culprit, in large part because symptoms such as nausea and vomiting, and even the more severe septicemia, can be caused by a wide variety of microbes. Unfortunately, Vibrio cases have been on the rise, and according to CDC’s most recent Food Safety Progress Report, we saw a 75-percent increase in cases in 2013 compared to 2006-2008, and a 32-percent increase compared to 2010-2012 in the U.S. The majority of these 2013 cases (62 percent, or 144 cases) were V. parahaemolyticus, and 9 percent (21 cases) were V. vulnificus. It is also believed that for every V. parahaemolyticus case that is reported, there are 142 cases that go undiagnosed. This is probably due to an underreporting of cases since many laboratories do not use the special culture media needed to grow the bacteria. To improve our understanding of the impacts of these bacteria, Vibrio infections were made a notifiable disease in 2007, which means that lab-confirmed cases have to be reported to state health departments, which then inform CDC. Unfortunately, we know considerably less about the significance of Vibrio infections in other parts of the world. For the love of the food, oyster aficionados have created some interesting myths about how to reduce their risk of disease from eating raw oysters, such as the notion that covering the oysters in hot sauce will kill bacteria. The old adage about only eating oysters in months containing an “r” has been around since the 1500s, and while the V. vulnificus levels in water are higher in the summer months, CDC says that 40 percent of cases actually occur in the “r”-containing months between September and April. Similarly, some people think they can tell when an oyster is not safe to eat, but Vibrio bacteria do not change the taste, smell, or appearance of shellfish. Thankfully, the bacteria are quite susceptible to heat. People can reduce their risk of infection by ordering cooked oysters when they go to restaurants, or, when preparing oysters at home, follow a few simple precautions, which are outlined at Foodsafety.gov. References: CDC. 2014. Notes from the Field: Increase in Vibrio parahaemolyticus Infections Associated with Consumption of Atlantic Coast Shellfish – 2013. MMWR 63(15): p. 335-336. Accessed athttp://www.cdc.gov/mmwr/preview/mmwrhtml/mm6315a6.htm?s_cid=mm6315a6_x CDC. 2014. Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food – Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2006–2013. MMWR 63(15): 328 – 332. Accessed at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6315a3.htm?s_cid=mm6315a3_w CDC. 2015. Vibrio illness (Vibriosis). Accessed at http://www.cdc.gov/vibrio/ FDA. 2014. Raw Oyster Myths. Accessed at http://www.fda.gov/Food/ResourcesForYou/HealthEducators/ucm085385.htm Foodsafety.gov. 2015. Vibrio infections. Accessed at http://www.foodsafety.gov/poisoning/causes/bacteriaviruses/vibrio_infections/

When a Norovirus Expert Got Norovirus

Liz Bradshaw — Mon, 06 Apr 2015 05:02:53 +0000

(This article by Liz Bradshaw, a postdoctoral research scholar in NoroCORE, the Norovirus Collaborative for Outreach, Research, and Education, based at NC State, is the fourth in a series leading up to April 7, when the World Health Organization will celebrate World Health Day, which is focused this year on food safety. The first article in the series can be found here, the second one is here, and the third is here.) Knowing about one in 15 Americans gets norovirus every year, I’ve had the “When the NoroCORE blogger got norovirus” post waiting in the wings for a while. I think the virus has a good sense of ironic timing. Through pure coincidence, one weekend last month was the Gastropocalypse in our home. My husband was first, with a sudden onset of some truly spectacular vomiting and diarrhea in the dead of night. Being the dutiful, loving spouse that I am, I left bleach, nitrile gloves, medications, and paper towels outside the bathroom door and set up basecamp in the guest room. Knowing my time might be nigh, since norovirus gets around (fun fact: it can be aerosolized over several feet when a person vomits) and has a 12-48 hour incubation period, I dashed to the grocery store at first light for enough bland foods, cleaning supplies, and tummy meds to last us a week. (In a perfect world, I would have had everything on hand ahead of time, and not risk spreading my cooties around, since you can shed the virus before showing symptoms, but we were laughably low on toilet paper.) Sure enough, by that night I was feeling pretty puny, with demonic tummy rumblings and waves of chills, aches, and nausea. Truth be told, we don’t know that it was actually norovirus and, if it was, we can only guess as to how we got it. Noroviruses are typically spread through direct person-to-person contact, through consuming contaminated food or water, or through encountering the virus in the environment. Hypothetically, someone with the virus on their hands could have touched the same doorknob or menu my husband used when he visited a restaurant over the weekend, or it could have been in the food he ate, and I likely got it from being in contact with him or our contaminated apartment. The key part to understanding the food safety aspect is that food can be contaminated at any point from farm to fork, and we usually associate foodborne norovirus outbreaks with foods that are served raw or minimally cooked, or, like the sandwich my husband ate, ones that are prepared by hand. About one-quarter of all norovirus outbreaks in the United States are associated with the consumption of contaminated foods. It is thought that 90 percent of people with norovirus do not seek medical attention and manage their symptoms at home, like we did, so those cases don’t get diagnosed, reported, and tallied by groups such as state health departments or the U.S. Centers for Disease Control and Prevention (CDC). But that doesn’t mean the illness isn’t a big deal, and we think that noroviruses are the leading cause of acute non-bacterial gastroenteritis — and the most common cause of foodborne illness in the U.S. Looking at the big picture, it’s estimated that 20 million Americans get norovirus each year, at a cost of $2 billion. Though the vast majority of people get better after a couple of memorable days, it is believed that as many as 800 people in the U.S., usually the young, elderly, or immunocompromised, die from the disease. When infected, people shed the virus in the millions to billions in their stool and vomit, and the virus can persist on surfaces, foods, and in water for weeks or more. However, there are several things people can do to prevent getting and spreading norovirus, which CDC does a great job of explaining. North Carolina State University plays a unique role in this story and in promoting public health by being the home institution for NoroCORE. NoroCORE stands for the Norovirus Collaborative for Outreach, Research, and Education, and it is funded through a $25-million grant awarded by the USDA National Institute of Food and Agriculture. The collaborative includes more than 30 research teams from 18 institutions around the country, and teamwork and bringing different disciplines together to make actual impacts are the name of the game. NoroCORE works toward its goal of reducing the burden of viral foodborne illness by approaching the problem from multiple angles in the form of six cores: Molecular Virology, Detection, Epidemiology & Risk Analysis, Prevention & Control, Extension & Outreach, and Capacity Building. Research is a big part of NoroCORE, to better understand the virus, how it affects us, and how we can manage it, but there is more to the picture. NoroCORE also gets feedback from around 100 stakeholder organizations to ensure that the research and tools that are developed are practical and relevant. NoroCORE also reaches out to other researchers in the field in the form of funding awards and fosters the next generation of food virologists by awarding annual graduate fellowships. For example, NoroCORE researchers here at NC State are investigating how far the virus particles can travel when a person vomits, its persistence in the environment, how analogs of the particles (termed virus-like particles) interact with detergents and surfaces, and how social media can be used to educate audiences about food safety. Some of our collaborative institutions are working on culturing the virus, understanding its spread within human populations, and developing better detection methods. In short, NoroCORE blends the expertise of researchers, educators, and Extension specialists from institutions around the country with the perspectives of those in industry and government organizations. Their goal is to bring about positive change and make advances in the fight against foodborne viruses, accomplishing more together than the relevant participating groups could do alone.