Of more than a hundred species belonging to the genus Vibriofour are the cause of the majority of health problems. Most people are at least indirectly aware of the conditions they cause.
Vibrio vulnificusthe species that has sickened people in Florida, is the microbe that most often hides under a headline-grabbing name: “flesh-eating bacteria.” This species, as well as Vibrio parahaemolyticus et Vibrio alginolyticuscontaminates shellfish such as clams and oysters, potentially decimating fish stocks and causing serious gastrointestinal disorders and dehydration in people who eat them raw or undercooked. Finally, the bacteria Vibrio cholerae is the cause of the diarrheal disease called cholera, which affects up to 3 million people worldwide each year and causes 95,000 deaths.
Dangerous species rarely appear in the Pacific Ocean; the strains of Vibrio vulnificus are endemic to the Atlantic Ocean and Gulf coastal waters. Even in their natural environment, scientists do not fully understand the role they play, although one of their functions is to degrade “marine snow” made of organic matter, says Salvador Almagro-Moreno.
Because vast expanses of ocean are low in the nutrients they need to survive, bacteria spend most of their time in a dormant state. However, when exposed to an influx of nutrients, they grow, multiply and proliferate.
The increase in cases near the west coast of Florida is largely due to contact with people who were immersed in infected water. “You have people out there trying to rehabilitate their property and they’re exposed to hot, stagnant water. This is exactly the kind of conditions in which Vibrio can grow,” says Maya Burke, deputy director of the Tampa Bay Estuary Program, which is responsible for ensuring that this West Coast estuary remains safe and clean.
It is also possible that the nutrients released in large quantities into the water by the storms favored the proliferation of the bacteria. This includes pesticides that have run off lawns, wastewater dumped into waterways through obsolete pipes and a by-product of fertilizer factories, phosphogypsum, which can be radioactive.
Checks carried out in Tampa Bay after the hurricane revealed its presence of the type Vibrioreveals Maya Burke, although the exact number and species are not yet known. The territory does not continuously monitor vibrio levels, she specifies.
When exposed to nutrients, they grow and proliferate rapidly in both the intestines and bloodstream of human beings. “It is one of the fastest growing organisms on Earth. They enter the host, find a warm and nutrient-rich environment, and proliferate very quickly,” describes Salvador Almagro-Moreno. The question of whether certain species of Vibrio remain in a dormant state inside the human body has not yet found a clear answer.
The bacteria can enter the body in different ways. Symptoms of exposure to dangerous strains through an open wound include redness, pain, swelling, discoloration, drainage, and ultimately dead, blackened skin. This is what inspired the nickname “flesh eater”. Ingesting contaminated seawater or seafood causes diarrhea, abdominal cramps and vomiting. If the infection spreads to the bloodstream, the first symptoms are fever, chills, and dangerously low blood pressure.
For 20% of people who contract an infection, known as vibriosis, it leads to death, sometimes within just one or two days.
What makes these bacteria so deadly is their ability to multiply quickly. “If you saw something strange on your finger or foot, you would seek treatment. But the problem is that you can be infected during the day and wake up the next morning with sepsis,” explains Salvador Almagro-Moreno.
“If you are infected, you have to act very quickly,” warns Mohammad Moniruzzaman, a microbiologist at the University of Miami. Most antibiotics, taken early enough, can treat it effectively. In severe cases, an infected wound may require tissue removal or even amputation. This is why Mohammad Moniruzzaman advises avoiding coastal waters in the event of an open wound, or at least protecting it with a water-resistant dressing.
Infections with Vibrio are particularly dangerous for older people, those with weakened immune systems, or those suffering from certain chronic illnesses. An article published in the medical scientific journal The Lancet brings to our attention that people with liver disease are two hundred times more likely to die from an infection Vibrio vulnificus than those with healthy livers.
The increase in the number of these bacteria, caused by climate change, is also impacting the seafood industry. Tilapia and shrimp farms, in particular, have been hit hard by outbreaks of Vibrio. An article published in the scientific journal mBio calls them a “growing problem for aquaculture worldwide.” In certain marine cultures, mortality rates have reached 80% after an epidemic, reports Salvador Almagro-Moreno. In rare cases, even oysters from Alaska have been affected.
As the waters of the east coast remain warmer until autumn, this allows species belonging to the genus Vibrio to proliferate and prosper over longer periods of time. The old saying to avoid raw oysters during months without the letter “r”, i.e. late spring and summer, may no longer be a safe guard. sufficiently effective. Currently, consumption of contaminated seafood leads to more than 50,000 cases of vibriosis in the United States each year, a number that is sure to increase as the bacteria proliferates. Salvador Almagro-Moreno suggests drawing inspiration from the New Orleans food traditions of frying or grilling clams and oysters rather than eating them raw.
Although there is no global monitoring system tracking the traces of Vibrio pathogens, countries are increasingly recognizing the risks they represent and taking action. The European Center for Disease Prevention and Control created a map in an effort to try to predict when conditions, such as ocean surface temperature and coastal salinity, are particularly conducive to blooms.
In the United States, the Centers for Disease Control and Prevention gathers information on cases from state public health officials, which can help trace the source in the event of an outbreak. The data is incomplete, with most cases of vibriosis not reported and figures not published every year, but it shows migration inland. In 2012, most monitored cases came from the Atlantic and Gulf of Mexico coasts. In 2019, infections in inland states jumped 10%, likely due to the introduction of contaminated seafood into those territories.
Further monitoring bodies of water that may contain these bacteria will become increasingly important as climate change continues to warm waters and the number of infections increases. It is in fact impossible to know, simply by observing the water before diving in, if they are present. “These are marine bacteria,” says Mohammad Moniruzzaman. “They thrive in water that appears clear and beautiful. »
