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Maryland woman catches rare tropical bacterial disease from her fish tank

A fancy-tailed guppy (Poecilia reticulata) in an aquarium.
(Image credit: Shutterstock)

A woman in Maryland contracted a rare bacterial disease from her home aquarium, according to a new report.

The disease, called melioidosis, is usually seen only in tropical areas outside of the U.S., and when cases do appear in the U.S., they almost always occur in people who have traveled to other countries. The Maryland case, which occurred in 2019 and is described in a report published Sept. 27 in the journal Emerging Infectious Diseases, is unusual because the woman had never traveled outside the U.S. Her case is also the first in the world to be connected to a home aquarium, the authors said.

Such non-travel-related cases of melioidosis are becoming more common, however. In August, U.S. health officials announced they were investigating four cases of melioidosis that occurred in 2021 and weren't tied to travel, Live Science previously reported. The sources of those cases still haven't been identified, but officials suspect that an imported product — such as a food, drink, personal care item or cleaning product — may be the culprit. The Maryland case doesn't appear to be connected to the 2021 cluster.

Melioidosis is caused by the bacterium Burkholderia pseudomallei, which grows in tropical climates and is most commonly seen in Southeast Asia and northern Australia, according to the Centers for Disease Control and Prevention (CDC). People can become infected through contact with contaminated soil or water, particularly if they have cuts on their skin, the report said. People can also catch the disease by drinking contaminated water or inhaling contaminated dust or water droplets.

Related: 11 ways your beloved pet may make you sick

The disease can cause a range of symptoms depending on where the infection occurs in the body. Symptoms of a lung infection include cough, chest pain and high fever; symptoms of a skin infection include swelling and abscesses; and symptoms of a bloodstream infection include headache, abdominal pain and disorientation, according to the CDC. Not everyone infected with the bacteria experiences symptoms, but in those who do, the disease can be serious, with a fatality rate between 10% and 50%, according to a 2019 paper in the journal The Lancet Infectious Diseases. (Among the four U.S. melioidosis cases in 2021, two died.) Certain medical conditions, including diabetes and liver disease, can increase a person's risk of infection, according to the CDC.

The 56-year-old Maryland woman, who had a history of diabetes, was first hospitalized in September 2019 with fever, cough and chest pain, and tests showed she had pneumonia. Several days later, further testing revealed that she was infected with B. pseudomallei.

She began receiving an antibiotic called meropenem, which is recommended for treating melioidosis. After 11 days, she was well enough to leave the hospital. But three weeks later, her infection relapsed even though she was still on antibiotics. She was hospitalized for another week and given a second antibiotic. Overall, it took 12 weeks of continuous antibiotics to clear her infection.

To determine where her infection came from, health officials took samples from in and around the woman's home, including samples from her two freshwater aquariums. Samples from one fish tank were positive for B. pseudomallei, and the bacterial strain in the tank was a genetic match to the one that infected the patient.

The woman reported that she had purchased the aquariums, tank supplies and several types of tropical fish, including cherry barbs (Puntius titteya) and fancy-tailed guppies (Poecilia reticulata), in July 2019.

She also reported that she had put her bare hands and arms into the tank while cleaning it, the report said.

So officials investigated the pet store where the woman bought the fish, as well as the vendors that imported the fish, to check for B. pseudomallei contamination.

"Because these vendors might distribute freshwater animals and aquatic plants to pet store retailers throughout the United States, identifying possible source(s) of introduction with B. pseudomallei in the supply chain is essential to public health," the authors wrote in their report.

As a result of the case, the CDC is now including questions about ownership of aquariums and tropical fish in questionnaires used for investigating melioidosis cases, according to Gizmodo.

The case "really broadened our understanding about how the bacteria might be able to travel across borders through imported products. And now that we've identified this new route of exposure, that can raise awareness about this risk," study lead author Patrick Dawson, an epidemiologist in the Office of Science at the CDC, told Gizmodo.

To reduce the risk of catching diseases from fish in general, the CDC recommends that people wash their hands before and after cleaning aquariums and feeding fish. People should also wear gloves to cover any cuts on their hands while cleaning aquariums or handling fish, according to the agency.

Originally published on Live Science. 

Rachael Rettner

Rachael has been with Live Science since 2010. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.