NEW YORK (Reuters Health) - Small water frogs marketed and sold as pets are linked to an outbreak of Salmonella infections from 2008 to 2011, according to a report from the U.S. Centers for Disease Control and Prevention (CDC).

Under a very high magnification of 12000X, this undated colorized scanning electron micrograph shows a large grouping of Gram-negative Salmonella bacteria. REUTERS/Janice Haney Carr/CDC/Handout/Files

The report published in Pediatrics on Monday found the infection sickened 376 people in 44 U.S. states and sent 29 percent of those infected to the hospital - mostly children.

“This was the first Salmonella outbreak associated with aquatic frogs, and in this case the frogs are often marketed as good pets for kids,” said Shauna Mettee Zarecki, the study’s lead author from the CDC in Atlanta.

“The majority of people didn’t realize there were any risks from these amphibians or reptiles, like turtles and snakes,” she added.

While most people hear about Salmonella-contaminated food, Mettee Zarecki said reptiles and amphibians also carry the bacteria. Humans can become infected after handling the animals, cleaning their containers or coming in contact with contaminated water.

People infected with Salmonella can have prolonged diarrhea, cramps, vomiting and a persistent fever. The infection can be deadly if it’s left untreated, and it’s most dangerous in the young, elderly and people with weak immune systems.

Previous research has found that reptiles and amphibians are responsible for about 74,000 Salmonella infections in the U.S. every year.

In the new report, Mettee Zarecki and her colleagues write that researchers from the CDC - along with state and local health departments - investigated an outbreak of Salmonella infections, mostly among children, in 2008.

By early 2009, the number of cases returned to normal before the researchers could find a cause. The investigation was started again when five more children were infected with the same strain of Salmonella in Utah later that year.

To find what was behind the outbreak, the researchers interviewed people who were infected with that strain of Salmonella from January 2008 through December 2011. They asked each person what animals and food they were exposed to in the week before they got sick.

They then compared the data from 18 people with that strain of the bacteria to 29 people who were infected with a different type of Salmonella.

Overall, they found 67 percent of the people in the new outbreak were exposed to frogs during the week before their illness, compared to 3 percent in the comparison group.

The majority of people who came in contact with a frog during the week before they got sick remembered the type - an African dwarf frog.

“Everything really linked these frogs with the illnesses,” said Mettee Zarecki.

The investigation eventually led to an African dwarf frog breeding facility in Madera County, California. There, researchers found the same strain of the bacteria in the facility’s tank water, tank cleaning equipment, water filters and floor drains.

The facility started distributing frogs again in June 2011, after the owner voluntarily shut down the operation and instituted cleaning measures.

The researchers write, however, that African dwarf frogs can live for five to 18 years, which means infected frogs may still be in homes and continue to cause illness.

“The important consideration with any aquatic pet is to provide adequate filtration to keep the water clean and perform regular partial water changes,” said Dr. Nicholas Saint-Erne, a veterinarian for PetSmart, Inc., in a statement to Reuters Health.

Saint-Erne, who was not involved with the new report, added that people with questions should ask veterinarians who specialize in aquatic animals or reptiles to help “ensure their pets are healthy and being given the proper care and nutrition.”

“If these aquariums are in homes, children under five (years old) shouldn’t be allowed to clean the aquarium,” said Mettee Zarecki, adding that also applies to people with weakened immune systems.

“Pets are wonderful. We think they’re a great learning tool for children, but some pets just aren’t appropriate for children or individuals” with weakened immune systems, she added.

SOURCE: bit.ly/HjQ8dI Pediatrics, online March 11, 2013.