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Pathogenic Vibrio Bacteria in the Indian River Lagoon and their Potential Threat to Human Health
Gabby Barbarite and Peter J. McCarthy
Vibrio bacteria are emerging pathogens responsible for 80,000 illnesses and 100 deaths in the United States annually. Infections are directly linked to the marine environment and are acquired through contaminated seafood or aquatic injuries. Florida has the highest national incidence of vibriosis, with 20% of its cases reported from the Indian River Lagoon region, a popular recreation destination.
This is the first systematic study of Vibrio vulnificus, V. parahaemolyticus and V. cholerae in the Lagoon, with the goal of understanding how, when, and where humans may encounter them in the environment. Using a combination of cultivation and molecular techniques, we have detected these pathogens in sediment, water, fish and shellfish collected from a series of sites. Preliminary findings suggest an important health concern and will be used to inform the public and medical care providers of these hazards to improve recreational safety.
Local Hazards Associated with Vibrio:
Vibrio naturally occur in estuaries like the Indian River Lagoon and are not a result of human pollution. Their presence is directly linked to temperature and salinity, being most abundant in warm (17-35 °C), brackish (5-25 ppt.) waters. Because of Florida’s warm climate, Vibrio are present in areas of the IRL year-round. V. vulnificus is most likely to be encountered in stagnant, inshore waters (especially near freshwater discharge) rather than in the ocean due to their inability to tolerate high salinities. However, events like rainfall, freshwater release, and low tides can temporarily move water containing these bacteria into areas where they are not normally present.
Local oysters, crabs, shrimp and fish carry Vibrio if they live in areas where it is present. Anglers should be aware of these hazards and use caution when handling fish and bait. Proper footwear should be used when wading to prevent injury. Open wounds should never be exposed to the environment and all seafood should be cooked thoroughly. Fear of V. vulnificus should not keep you out of our local waters this summer- it’s always been here, only a small percent of the population is considered “at risk” and infections are easy to prevent if you follow the safety recommendations below.
Important information for concerned citizens, the fishing community, seafood consumers, healthcare providers, media teams and educators
Florida is a tropical paradise that attracts marine enthusiasts and seafood lovers from around the world! Its extensive waterways not only offer unique areas for us to explore but also provide essential habitat for marine life. Although you can’t see them, a group of marine bacteria known as Vibrio is common throughout local waters. As natural inhabitants, they play an important role in environmental processes and are associated with many aquatic organisms. Under certain conditions, however, these bacteria are capable of causing diseases such as wound infections and seafood sickness. Vibrio can be encountered through activities like fishing and swimming or by eating raw oysters and fish. Don’t let some of the things you’ve heard keep you from your favorite activities, infections are rare and easy to prevent! By being aware of these hazards and following a few safety guidelines, you can ensure that your time on the water is as safe and enjoyable as possible!
What are Vibrio?
The name Vibrio refers to a large and diverse group of marine bacteria. Most members are harmless and can actually benefit the ecosystem by breaking down organic matter or providing food for larger organisms. Vibrio are part of the natural microflora of many marine animals such as oysters, clams, shrimp, crabs, and fish.
Some strains produce harmful toxins and are capable of causing a disease known as “vibriosis”. About 15 species are known to infect humans, two of particular concern are Vibrio vulnificus and Vibrio parahaemolyticus. The presence of these pathogens cannot be detected by the naked eye and specific laboratory techniques are necessary to confirm their identity.
Where and when are they found?
Vibrio naturally occur in coastal waters world-wide. They are not a result of pollution and can be present even if the water looks clean. Species that infect humans are most common in brackish environments, which are areas where freshwater mixes with saltwater. Contrary to popular belief, V. vulnificus and V. parahaemolyticus are typically found in estuaries and bays rather than the beach or ocean due to their inability to tolerate high salt levels.
Though present in Florida waters year-round, Vibrio are most abundant from April to November, when temperatures are the warmest. These natural peaks correspond with an increase in human infections, which are usually highest during the summer months. High concentrations can be encountered in stagnant inshore areas, especially near freshwater discharge sources. Events like rainfall, water release and tidal fluxes can move these pathogens in to areas where they are not normally present.
Who is at risk for infection?
Most people are NOT at risk for developing illness. If encountered, a healthy immune system will combat infection and may only result in mild symptoms. However, people with weakened immune systems can develop life-threatening infections. Some high risk conditions that increase susceptibility include: liver disease, alcoholism, diabetes, hepatitis, hemochromatosis (iron overload), stomach disorders, HIV/AIDS, cancer, and long-term steroid use. Severe illness almost exclusively occurs in individuals who have these risk conditions. These patients are 80 times more likely to become ill and 200 times more likely to die. Though these cases are rare, they can be very serious and progress rapidly. Seek treatment immediately if you suspect infection.
How can people become infected?
In order for infection to occur, pathogenic Vibrio strains must enter the body of a susceptible individual. This is usually a result of consuming raw and contaminated seafood or through the prolonged exposure of a wound to areas where they are present. Activities that may result in contact with these bacteria include fishing, wading, and swimming as well as cleaning and eating seafood, especially during summer months.
Recently, the term “flesh eating bacteria” has been used to refer to Vibrio. This description is not only false and misleading, but it causes unnecessary fear and panic. These bacteria do NOT decompose healthy-intact skin, even if contacted for long periods of time. Infections are acquired when pathogenic strains encounter broken skin and open wounds, or are consumed in large quantities. Only after entering the body through these processes are they capable of causing disease in certain individuals. Tissue breakdown or “necrosis” can occur during advanced stages of vibriosis but is only associated with severe infections.
Vibriosis Incidence and Statistics in the US
It is estimated that Vibrio cause up to 80,000 illnesses, 500 hospitalizations and 100 deaths in the United States each year. Clinical characteristics of disease include gastroenteritis, tissue infection and primary septicemia. V. parahaemolyticus is responsible for most of the national cases (46%), however disease caused by this bacterium is usually mild, with low hospitalization (25%) and death (2%) rates. Infection from V. vulnificus is less common (13% of total US cases), however it causes the most severe illness, with the highest hospitalization (87%) and death (32%) rates.
Half of the reported illnesses are food-borne, primarily associated with V. parahaemolyticus. These are acquired by consuming raw and contaminated seafood, such as oysters (64%), shrimp (14%), crab (8%), clams (7%), and fish (7%). The remaining cases are non-foodborne, primarily associated with V. vulnificus. These infections are contracted through aquatic injuries via wound exposure (76%), marine wildlife (13%), and handling seafood products (9%).
Looking locally: Florida Cases
Sixty seven percent of US cases are reported from the Gulf and Atlantic coastal regions due to water parameters suitable for Vibrio as well as activities like seafood harvest and marine recreation. This is especially true for Florida, which has the highest national incidence of vibriosis. Over the last decade, the state reported an average of 133 cases a year. Most recently, in 2014, there were a total of 167 reports of vibriosis; V. vulnificus was responsible for 32 infections and seven deaths, V. parahaemolyticus caused 30 infections and one death.
This may seem alarming at first, but infections are actually quite rare considering the millions of people that participate in water activities and consume local seafood each year. In fact, only a small percent of the population is actually classified as high risk for developing infection. The fear of becoming infected should not keep you from enjoying your favorite recreational activities or seafood dishes. The good news is that these infections are very easy to prevent if you use good safety and hygiene practices.
Should I be worried about Vibrio at the beach?
Most disease-causing species are found in brackish waters, the ocean is typically too salty for them to tolerate. You’re more likely to encounter Vibrio inshore than at the beach, however, events like freshwater release, rainfall and low tides can temporarily move them into areas they are not normally found.
Is Vibrio really “flesh eating”?
No! Vibrio cannot break down healthy, intact skin on contact. In order for infection to occur it must actually enter your body through prolonged exposure of an open, unhealed wound (or be consumed, usually through raw seafood). This is not a medical term and was likely derived from the fact that tissue death can occur during late stages of infection (around the wound if untreated, especially in those with weakened immune systems). Proper first aid practices and a healthy immune system can combat Vibrio infections.
Is it safe for my children to go in the water?
Infections from Vibrio vulnificus and V. parahaemolyticus typically occur in patients that are middle-aged and elderly. Children are not considered “high risk” for developing infections unless they have weakened immune systems due to underlying disease. Regardless, it is never a good idea to expose unhealed wounds to the environment. Another species, V. alginolyticus, is known to cause mild ear infections in children but can be easily prevented by cleaning and drying ears if they have water in them after swimming.
What should I do if I’m injured during water activities?
Always treat injuries as soon as they happen. Clean the wound thoroughly with soap and water, removing any foreign material or debris. Rubbing alcohol or peroxide and antibiotic ointment should be used in larger/more severe injuries or punctures. Cover the area with a bandage and prevent further exposure until fully healed. If the area becomes swollen, hot or very painful and you suspect infection seek medical treatment immediately.
Is it safe to eat local seafood?
Yes! The easiest way to prevent food-borne Vibrio illness is to avoid eating it raw. Seafood that has been properly cooked and handled should not contain Vibrio bacteria. Many hazards exist when you consume raw seafood, especially shellfish. If you plan on eating raw fish or oysters be sure to get them from a reputable source to ensure they have been processed properly. People with weakened immune systems or those that are considered “at risk” for infection should not consume raw seafood.
Am I at risk for Vibrio infection?
Typically health issues like liver disease, alcoholism, diabetes, hepatitis, hemochromatosis (iron overload), stomach disorders, HIV/AIDS, and cancer can put people at risk for Vibrio illness. Most healthy people are not considered “at risk” and may only experience mild symptoms. Fishermen and seafood processors should be particularly cautious and aware of these infections. Contact your doctor if you are unsure or would like more information.
I only need to worry about Vibrio in the summer?
Because of Florida’s warm climate, Vibrio are present in brackish waters year-round. They are most abundant in the summer and early fall when the water is the warmest. People are also more likely to participate in water activities during these months. The combination of these factors contribute to a peak in reported cases during the summer.
Are human activities like pollution responsible for Vibrio in Florida’s waters?
No. Vibrio are a group of marine bacteria that naturally occur in local waters and were not introduced by terrestrial pollution. They play an important role in environmental processes and can actually help break down organic matter. However, human activities (like freshwater discharge) can alter Vibrio distribution by moving them into and allowing them to persist in areas where they normally do not.
I haven’t heard of Vibrio until recently. Are illnesses in Florida new or increasing?
Incidence of disease in Florida is typically higher than other parts of the country because of its warm weather, extensive coastline, and marine recreation. Though likely occurring before, Vibriosis has been documented in Florida throughout the last 40 years. Over this time the number of annual cases has increased. This could be due to improvements in medicine and technology (facilitating diagnosis, reporting, and communication) as well as increasing tourism (more people participating in water activities). Currently, there is no evidence that Vibrio levels in the environment have increased.
Don’t let some of the things you’ve heard keep you from your favorite activities: Infections are rare and easy to prevent! By being aware of these hazards and following a few safety guidelines, you can ensure that your time on the water is as safe and enjoyable as possible!
Hazards associated with Vibrio-related wound infections are greatest:
- In stagnant, inshore waters and during warm, rainy months due to high natural abundances
- When a wound is submerged for a long period of time or an injury goes untreated
- For individuals with weakened immune systems or underlying disease
First Aid and Wound Care:
- Wash the wound thoroughly with soapy water and remove any foreign material
- Follow with rubbing alcohol or peroxide, antibiotic ointment, and cover with a bandage
- Avoid further contact with the environment and keep the area clean until it has healed
Swimming and wading
- Always access the water from a non-obstructed area where the bottom is visible. Be aware of hazards like submerged objects and wildlife.
- When wading, use puncture-resistant footwear with a good grip. Exercise caution on slippery surfaces like boat ramps, rocks, and kayak launches.
- Clean gear and wash off after being in the water, especially before handling food
Advice for Anglers: Fish Handling
- Keeping a fish in the water increases its chance of survival and reduces its ability to injure the angler. Decide ahead of time what you intend to keep, and release unwanted fish right away.
- The proper use of a release tool can help remove hooks safely and quickly. If you plan to retrieve the fish, use a landing tool or pliers to minimize handling.
- Circle hooks are recommended because they are more likely to catch a fish in the jaw, making removal easy. If the fish swallows the line or removal is too difficult, cut it as close to the hook as possible. Non-stainless steel hooks will likely fall out over time.
- If handling the fish cannot be avoided, use a wet towel or gloves to protect yourself. Be aware of areas that can cause injury like spines, barbs, and teeth. If you plan to keep the fish, place it on ice immediately.
- Always wash your hands thoroughly after fishing, especially before handling food. Be sure to clean your gear after each use with special care for sharp objects like hooks and knives.
- Live bait like shrimp, crabs, and small fish, can also carry Vibrio. Use caution when hooking or handling, paying attention to areas that can inflict injuries like spines, shells, and claws.
- Bait buckets can be reservoirs for Vibrio, since they accumulate bacteria from waste produced by the animals they contain. Do not over-stock the container and be sure to exchange its water frequently. Use a handnet to retrieve bait and never submerge wounds.
Hazards associated with Vibrio- related seafood sickness are greatest:
- During the summer months, especially in coastal areas due to high natural abundances
- When consuming raw, undercooked, or contaminated cooked seafood - especially shellfish
- For Individuals with weakened immune systems or underlying disease
Here are a few ways shellfish can be prepared:
For shellfish still in the shell, either: (1) Steam until the shells open, then continue cooking for 9 minutes. (2) Boil until the shells open and continue to cook for another 5 minutes. Never eat shellfish that do not open during cooking.
For shucked oysters. either: (1) Boil or simmer for at least 3 minutes or until edges curl. (2) Fry in oil at 375°F for at least 3 minutes. (3) Bake at 450°F for at least 10 minutes. (4) Broil 3 inches from heat for 3 minutes.
Fish: Tips for safely preparing your catch
- Place fish in a cooler with plenty of ice immediately after catching. Ensure that it stays cold, as warm, moist conditions can promote Vibrio growth.
- Before preparing, thoroughly wash your hands and continue to clean them throughout the process. Discard all fluids left in the cooler and wash. Rinse the fish with clean water, remove mucous or debris with a paper towel.
- Place the fish on a clean surface and fillet, with special care not to contaminate the meat. Rinse each piece and set in a container or plastic bag. Keep unwanted fish scraps together and dispose of them immediately. Disinfect the area and all tools used.
- Meat that will not be prepared at that time should be immediately placed in the refrigerator (if eating within 2 days) or freezer (for long term storage).
- Cook fish at 450°F and ensure the internal temperature reaches 145°F. Cook for 10 minutes for each inch of thickness. This time can be doubled for unthawed, frozen fish.
- Place cooked and ready to eat fish in clean containers, never use the original unwashed utensils. Label leftovers with the contents and date then promptly refrigerate.
Florida Health Department:
- Vibrio vulnificus Information: www.floridahealth.gov/diseases-and-conditions/vibrio-infections/vibrio-vulnificus
- Florida Case reports and Statistics: FloridaCHARTS.com
- V. vulnificus Fact Sheet
Gateway to Vibrio vulnificus Info for Heath Care Providers, Educators, Consumers and Fishermen:
Centers for Disease Control & Prevention:
- CDC Cholera and Other Vibrio Illness Report for 2012
- Vibrio Illness in Florida from 1998-2007 by K. Weis
- Vibrio Wound Infections by J. Oliver
- Food and Drug Administration: www.fda.gov/Food/ResourcesForYou/HealthEducators/ucm085365.htm
- Risk of Eating Raw Shellfish
- V. vulnificus and Shellfish Fact Sheet
- General seafood safety
- Florida Sea Grant: http://catchandrelease.org/
- Florida Fish and Wildlife: http://myfwc.com/fishing/saltwater/recreational/fish-handling/
- Catch and Release Publication
In the News:
Social Media Accounts:
- Florida Department of Health
- Florida Sea Grant
- Harbor Branch at FAU
Funding for this project was provided by The Harbor Branch Foundation, HBOI Save Our Seas Specialty License Plate, Gertrude E. Skelly Charitable Foundation and NOAA Cooperative Institute for Ocean Exploration, Research and Technology. This content was provided by Gabby Barbarite (HBOI/FAU), Peter McCarthy (HBOI/FAU) and Holly Abeels (Florida Sea Grant).
Centers for Disease Control and Prevention (CDC). Cholera and other Vibrio illness surveillance (COVIS), summary data, 2012. Atlanta, GA: US Department of Health and Human Services. CDC, 2014.
Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Disease, Division of Foodborne, Waterborne, and Environmental Diseases, Vibrio Illness (Vibriosis), Vibrio parahaemolyticus. Retrieved June 5, 2015 from http://www.cdc.gov/vibrio/vibriop.html.
Drake, S. L., DePaola, A., & Jaykus, L. A. (2007). An overview of Vibrio vulnificus and Vibrio parahaemolyticus. Comprehensive Reviews in Food Science and Food Safety, 6(4): 120-144.
Food and Drug Administration. 2012. Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins. Second Edition. [Vibrio parahaemolyticus, pp. 26]. http://www.fda.gov/Food/FoodborneIllnessContaminants/CausesOfIllnessBadBugBook/default.htm
Oliver, J (2005) Wound infections caused by Vibrio vulnificus and other marine bacteria. Epidemiology & Infection 133: 383-391.
The Risk of Eating Raw Molluscan Shellfish Containing Vibrio vulnificus. Retrieved June 9, 2015 from http://www.issc.org/client_resources/Education/English_Vv_Risk.pdf.
Weiss, K.E., Hammond R.M, Hutchinson R., & Blackmore C.G.M. (2011) Vibrio Illness in Florida 1998- 2007. Epidemiology and Infection, 139: 591-598.
Wright, A.C., Goodrich-Schenider, R., Hubbard, M.A., and Schneider, K.R. July 2009. Preventing Foodborne and Non-foodborne Illness: Vibrio parahaemolyticus. FSHN09-01. Gainesville: University of Florida Institute of Food and Agricultural Sciences. Retrieved June 5, 2015 from http://edis.ifas.ufl.edu/fs146.