Flesh-Eating Bacteria Easy To Avoid, Just Swim In Gulf, Not Bays Expert Says
By Ben Raines, AL.com, July 6, 2016
The flesh-eating bacteria lighting up news reports all along the Gulf Coast has been around forever and is almost entirely avoidable if you know where to swim, said the nation’s leading expert on the deadly bacteria.
Andy DePaola was the lead seafood microbiologist and subject matter expert for the U.S. Food and Drug Administration until he retired last fall. His specialty was Vibrio vulnificus, the bacteria responsible for a string of high profile deaths and amputations this summer among beachgoers.
DePaola, who lives on Mobile Bay, said almost all cases of infection by the bacteria occur in brackish water, rather than the full saltwater of the Gulf of Mexico.
“There are absolutely safe places to swim, which are the front Gulf beaches. That’s where 90 percent of the people are,” DePaola said, referring to the beaches east of Fort Morgan, including Gulf Shores, Orange Beach, Pensacola and along the Panhandle of Florida. “If you are in Mobile Bay or any of our inside waters, pretty much everywhere you go is higher risk, even up to where you use a freshwater fishing license, above the bridges on Fish River or Dog River. Anywhere in the Mississippi Sound is another area of higher risk.”
The issue, DePaola said, is salt. Vibrio bacteria perish in the salty waters of the open ocean.
Vibrio vulnificus, which can also cause fatal bacterial infections in people with impaired livers or immune systems who consume raw oysters, is always present in our inshore coastal waters. In the summer, the bacteria blooms dramatically when water temperatures rise above 68 degrees.
“It’s really a Memorial Day to Labor Day issue. If the water is warm enough to be comfortable to swim in, you start having the risk. But only in brackish water, where the salinity gets below about 30 parts per thousand,” DePaola said.
Salinity is measured in parts per thousand. The water in the open Gulf of Mexico is usually around 35 or 36 parts per thousand. Those high salinity levels are relatively constant, both offshore and right up to the edge of the sand at the beach. The inshore waters, however, such as Mobile Bay, which have a lot of freshwater flowing in from rivers can vary from high levels of salt in the early fall to being almost purely fresh in the late winter and early spring when floodwaters are high.
Right now, Mobile Bay’s salinity measures at about 15 parts per thousand at Middle Bay Light. A meter at the Dauphin Island Sea Lab shows salinity in the lower bay has varied from about 15 parts per thousand to about 25 this week, all within the preferred range for Vibrio. Levels in the Gulf remain about 35 parts per thousand yearround. You can check salinity at various locations around Alabama’s coast through the Dauphin Island Sea Lab’s monitoring network.
Among the recent cases, one was contracted in Biloxi, Miss. That would involve swimming in the low salinity waters of the Mississippi Sound. Likewise with another case contracted in Grand Isle, Louisiana, near the mouth of the Mississippi River. Again, a place with lower salinity levels than most Gulf beaches. Low salinity, brackish water is almost always implicated in Vibrio cases.
“The World Health Organization did a study looking at Vibrio in oysters. What they found was the optimum range was around 17 parts per thousand. Once you got about 33 parts per thousand, there was no risk,” DePaola said. “Those levels are applicable for exposure while swimming as well.”
Little is known about how common vibrio infections related to swimming and fishing are. The federal government only tracks exposure from eating oysters. There is no database looking at infections contracted by people who were swimming with an open wound or cut while fishing or cleaning seafood. DePaola said there is some belief that people who are regularly in contact with brackish water are less likely to develop an infection than someone who has never been to the beach.
“If we did have the data, we would see that where you were swimming, and at what time of year, could make all the difference,” DePaola said. “But these infections, even in the inshore waters are fairly rare. For most healthy people, there is very little risk. I live on Mobile Bay and I am in the water all the time, almost every day, with cuts all over me. For me, and for many people, it is an acceptable risk.”
The key, DePaola said, is recognizing the signs of an infection and seeking medical treatment right away.
“The thing about contracting vibrio from a cut is you don’t have to have an underlying chronic illness, like with exposure from oysters. You can become infected even if you are healthy,” DePaola said. “If you are in the water and have a preexisting wound, or get one while you are swimming, you should be even more careful treating it with peroxide or whatever than you would on land. If you start having the edema, or start seeing the red streaks on your skin, it is critical to get immediate medical attention. Once it gets in your bloodstream, the bacteria multiples exponentially in a few hours. You can go from feeling ok to being very sick very quickly, in hours. You can end up dead in a matter of days.”
A common exposure pathway for fishermen involves the bait bucket. Because small fish, such as croakers, and crustaceans such as shrimp, often have high levels of vibrio in their guts, the water in a bait bucket can develop high levels quickly. A fin poke, or getting stuck with the horn on a shrimp, can lead to an infection.
“If a piece breaks off in your skin, that’s a place a micro-colony can grow,” DePaola said. “Also handling seafood. If you are peeling crabs or shrimp, you should assume you are being exposed, that they came from somewhere with the bacteria.”
Vibrio vulnificus, DePaola said, is one of the most common bacteria in our coastal waters, capable of reproducing rapidly. It is ever present, and was long before the BP oil spill, despite a common sentiment blaming the presence of the bacteria on the spill.
“In most of the world, Australia, Asia, on the Pacific Coast, it’s just too salty or too cold. But here along the Gulf, where you have estuaries with marshes and shrimp and crabs, that’s where you have the risk,” DePaola said. “If you love to swim, fish, shrimp, crab, it is a risk most people are willing to take. But you must understand that if you have the signs of an infection it is critical to seek treatment immediately. That’s just critical.”
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