OutLook For the Bay – LAST WORDS
Just When You Thought It Was Safe …
Mighty Microbes in the Bay
On May 1, 2012, Aimee Copeland, a fit, 24-year-old graduate student from Georgia gashed her leg when she fell from a zip-line into the Tallapoosa River near her home. The limb soon became infected. As the infection spread, Ms. Copeland fought for her life. After seven surgeries, and the amputation of one leg, the foot on her other leg, part of her abdomen and both hands, the young woman finally recovered.
Aimee had suffered from necrotizing fasciitis, a flesh-destroying bacterial infection. The responsible microbe, Aeromonas hydrophila, is common in fresh and brackish water environments, including the Chesapeake Bay. It’s not the only bacterium that causes the affliction; species of Streptococcus, Staphylococcus, Clostridium and Vibrio—also found in the Bay—have been implicated as well. And there have been reported cases of necrotizing fasciitis in people exposed to Bay waters.
So do Chesapeake Bay microbes threaten human health? Based on the spate of publicity following Aimee Copeland’s terrible ordeal, it might seem so. After all, the Bay is a veritable microbial soup. Its waters harbor up to 20 million bacteria per milliliter, more than almost every other body of water on earth. The high levels are mostly due to the Bay’s natural oceanographic features and circulation patterns, but organic pollution is also a factor. The microbes include some notorious species that routinely sicken both humans and fish. Vibrio bacteria are particularly concerning. They can cause severe gastrointestinal illness if ingested, e.g., with contaminated shellfish, nasty skin infections if the organism enters an open wound and even death. Vibrio vulnificus is implicated in 90 percent of deaths related to eating contaminated seafood. Bay waters could also expose unwary or unlucky persons to Norovirus, Hepatitis A, salmonella and the highly contagious, virtually untreatable Methicillin-resistant Staphylococcus aureus (MRSA).
And then there is Pfiesteria, the so-called “cell from hell.” Pfiesteria is a type of algae, specifically, a single-celled dinoflagellate, not a bacterium. The organism was suspected in major fish kills in the Chesapeake Bay in the 1990s. Then it was reported that fishermen and lab workers exposed to Pfiesteria suffered skin, respiratory, cognitive and neuropsychological effects. This resulted in national media frenzy, a flurry of research activity and no shortage of panic up and down the Bay.
So now you’re thinking, no way are you going back in the water, not even immerse your little toe. That would be, to put it mildly, an overreaction. The overwhelming majority of microbes in the sea, including bacteria, —are harmless to humans and beneficial to their environment. They play an important role in marine ecology, including serving as a food source for other sea creatures and helping to break down dead organic matter. Some bacteria even consume petroleum, making them an effective cleanup agent after an oil spill.
That’s not to say we should ignore the pathogenic microbes. But necrotizing fasciitis and Vibrio infections are rare in the mid-Atlantic region. Illness caused by Aeromonas hydrophila is almost unheard of. There are about 30 cases of Vibrio infections annually in each Maryland and Virginia and perhaps one death a year. There is no evidence that these numbers have been recently increasing.
Immuno-compromised individuals are most susceptible, and antibiotics are usually effective if the illness is treated in time. And the cell from hell? Pfiesteria hysteria seems to have faded with the passage of time, and there is no substantive information to support fears that a dangerous new organism is rampant in the Bay.
Still, prudence is advised when it comes to Bay microbes. To minimize the chances of bacterial infection, a few simple precautions are in order. It’s always a good idea to thoroughly cook seafood. (OK, I do like my raw Chesapeake Bay oysters.) If you wade into the local waters, wear sturdy foot gear. Don’t expose cuts, scrapes, infected bug bites or open wounds to the water. If you have been exposed, wash thoroughly with soap and clean water as soon as possible. Be particularly cautious with children and older adults. Check state and county health department websites for swimming advisories before heading to the beach. Both states maintain Google Earth programs that notify the public about beach closures (see www.marylandhealthybeaches.com and www.vdh.state.va.us/epidemiology/DEE/BeachMonitoring/beachadvisories) And think twice about going into the water after a heavy rainfall. Maryland and Virginia recommend waiting for 48 hours.
There is some good news related to the sensationalized publicity about nasty aquatic microbes: It has helped to focus more attention on pollution in Chesapeake Bay, with some positive outcomes. For example, concerns that excessive nutrients running into the Bay might be fueling blooms of bacteria and harmful algae led to the Maryland Water Quality Improvement Act of 1998 with its requirement that farms must develop and implement nutrient management plans. We still have a long way to go before we clean up the Bay, but we are moving in the right direction.
The bottom line? It’s safe to go back in the water.
Henry, a former marine science instructor at the University of Massachusetts is currently an adjunct associate professor at Georgetown University and a biodefense specialist. He can be reached at firstname.lastname@example.org