Warmer Seas Drive More Bacterial Infections, Threatening Fishermen, Public Health

By Will Atwater

Last month, three people died as a result of infections from a category of bacteria you’ve likely never heard of: Vibrio. It is commonly present in coastal and brackish water, especially during warmer months.

“There are almost 80 described species of Vibrio that live in the water,” said UNC Chapel Hill Institute of Marine Sciences researcher Rachel Noble. But Noble also noted that as the seas warm through to climate change, there’s more Vibrio in North Carolina’s waterways.

According to a news release from the N.C. Department of Health and Human Services, there have been 47 recorded cases and eight deaths from infection caused by Vibrio microorganisms since 2019.

One way that people get infected with the bacteria is through eating undercooked seafood. Another way is the bacteria getting into a cut or scrape in the skin when exposed to water containing Vibrio. In people with weakened immune systems, a Vibrio skin infection can all too quickly lead to a systemic infection that can lead to loss of limbs or, left untreated, death.

Noble is among the experts who predict that in the future, Vibrio cases will pop up in places that previously had no issues, and they indicate that there will be more infections in December and January, for instance, since coastal waters are not cooling as much as in the past. .

Noble said that when she began testing the Neuse River estuary for Vibrio two decades ago in the winter, she found anywhere from three to ten microorganisms per 100 milliliters (a tenth of a liter) of water.

“Twenty years later, those numbers are closer to 100 to 200 per 100 milliliters in January.”

“There has definitely been not only an extending of the summer infection season,” she said, “but there’s also been a trend that it’s no longer true that our estuaries go down to almost zero in concentration in the winter months. They don’t. The Vibrios [bacteria] are still very much there.”

Climate change and Vibrio

Vibrio bacteria thrive in warmer, brackish waters where blue crabs live, especially when they’re molting and losing their hard outer shell. And one of the prime ways people get infected is when the bacteria gets into small cuts and scrapes.

Those small nicks in the skin have the potential to be a big issue for people like commercial fisherman Keith Bruno.

Bruno migrated to North Carolina from Long Island, where he once fished for lobster. After an outbreak of West Nile virus in New York in the 1990s, the regions around Long Island Sound aggressively sprayed for mosquitoes that carry the virus. Bruno is among those who blame the spraying for the collapse of the lobster fishery there. But around the same time, the waters in Long Island Sound began to warm, likely delivering the lobsters a fatal blow.

Now, the waters off the North Carolina coast, where Bruno harvests blue crab, are warming. The Vibrio bacteria threaten commercial fishers and those who work and play  in or near coastal estuaries and marshes. In the wake of Hurricane Florence in 2018, there were a number of Vibrio incidents.

And with that warming water comes more risk to Bruno and other fishers, who often get cuts and scrapes over the course of their work day.

Because of a medical condition, Bruno leaves most of the handling of crab pots to his son these days. But, he said, the risk of infection is part of the job.

“We are constantly getting scratched and cut and bit and jammed and poked,” said Bruno, who recounted being scratched from handling crab pots and fishing gear and being poked by bones protruding from buckets of bait.

“If anybody gets a wound in the water, they need to get medical attention right away,” said Dr. Michael Somers, an emergency medical physician at CarolinaEast Medical Center in New Bern. “We can … treat the infections, but better than that we can give medication to prevent the infection.”

If people who may have been exposed to Vibrio seek immediate medical attention, they can be prescribed an antibiotic such as doxycycline to protect themselves against developing the infection, Somers said.

Bruno said to save time, he and other fishers rely on bleach to prevent infection while out on the water.

“The down and dirty is ‘throw some bleach on it and get back to work,’” he said. “We live to work and work to live … We’re not going up to the walk-in clinic for antibiotics every time we get scratched — we’d live there and never make any money.”

There’s something in the water

A research article published in March 2023 supports the idea that Vibrio is spreading northward along the Atlantic Coast. That study bolsters a growing body of research showing that warming seas are driving more bacterial infections in more northern climes.

To better track the bacteria, the CDC partnered in 1989 with the Food and Drug Administration and four Gulf Coast states — Texas, Louisiana, Alabama and Florida — to develop the Cholera and Other Vibrio Illness Surveillance. The surveillance has now expanded and includes Vibrio data for the Atlantic Coast states.

Noble said that two forms of Vibrio are of particular interest to researchers and public health officials in the state: Vibrio vulnificus and Vibrio parahaemolyticus. V. vulnificus infections usually occur from exposure to brackish water, and V. parahaemolyticus is associated with eating undercooked shellfish.

The Centers for Disease Control reported in an email that in 2019, there were 158 Vibrio vulnificus infections. Twenty-one percent of the infections resulted in deaths — roughly one-half of V. vulnificus infections occurred in Gulf Coast states, and about one-third were in Atlantic Coast states.

When it comes to V. parahaemolyticus, the agency estimates about 52,000 people contract it annually from shellfish. While it will make a person miserable, with vomiting and stomach cramps, it has a very low death rate.

One of the three North Carolina deaths was someone who both ate seafood and waded in brackish water, so it’s unclear whether food or water exposure killed them.

Typically, healthy individuals infected with Vibrio have mild reactions. However, the CDC reports that individuals with underlying health conditions “are more likely to develop V. vulnificus or severe complications such as septicemia,” according to the email.

Protective measures

Sheila Davies, director of public health with the Dare County Department of Health & Human Services, understands the challenges faced by crabbers and fishers, but she strongly advises anyone to seek medical attention as soon as possible if they have scratches or cuts that have been exposed to brackish water.

“If you’re getting cut on a fishing hook, or crab pot or barnacles hanging … it increases your risk of infection,” she said. “So [I’m] strongly promoting how important it is to seek medical attention.”

Echoing Davies’ concern, NCDHHS included the following suggestions designed to help people avoid a Vibrio infection:

• If you have a wound (including from a recent surgery, piercing or tattoo), stay out of saltwater or brackish water, if possible. This includes wading at the beach.
• Cover your wound with a waterproof bandage if it could come into contact with saltwater, brackish water or raw or undercooked seafood.
• If you sustain any type of wound while in salt or brackish water (e.g., cutting your hand on a boat propeller or crab pot) immediately get out of the water and wash with soap and water.
• Wash wounds and cuts thoroughly with soap and water after contact with saltwater, brackish water or raw seafood.
• Thoroughly cook all shellfish to an internal temperature of at least 145 degrees Fahrenheit for 15 seconds, according to the U.S. Department of Agriculture.

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This article first appeared on North Carolina Health News and is republished here under a Creative Commons license.

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Photo credit: Fredrik Öhlander on Unsplash