An investigation into African dwarf frogs has found that they are responsible for a nationwide outbreak of a specific Salmonella strain among young children in the US.
The Salmonella Typhimurium Outbreak Investigation Team has been looking at the effects on the health of people who keep these amphibians as pets, following clusters of infections beginning in late 2008.
376 cases of the Salmonella strain were reported from 44 states between 2008 and 2011 - and 69% were in children less than 10 years of age. 29% of those who were infected were hospitalised.
Researchers interviewed those who had been been infected, asking what foodstuffs and animals they had been exposed to before they became ill.
67% of those interviewed had been exposed to frogs and, of those who knew the type of frog concerned, 79% said it had been an African dwarf frog. Most had been infected through indirect exposure - from the aquarium water or its habitat rather than handling the frog itself.
Tests on water in aquariums housing these frogs at homes, pet shops and day care centres showed it carried the same strain of Salmonella that had causes the outbreak.
Eventually the investigation led to an African dwarf frog breeder called in Madera County, California, where S. typhimurium was found in aquarium water, eggs, filters, maintenance equipment and floors.
The owner of the breeding facility voluntarily closed the business for several months and has since re-opened after a thorough clean-up operation, but the site is still monitored.
However, researchers are concerned that some of the original frogs may still be in aquariums around the country, as they can live anywhere between 5-18 years if properly cared for.
African dwarf frogs frogs are marketed as good children's pets and are popular in the US, where they are often sold as educational 'toys' in small plastic tanks.
But researchers say many people don't realise the risk.
"Amphibians and reptiles should never be kept in homes with children less than five years old or with people who have immune deficiencies," said lead author Shauna Mettee Zarecki.
Previous research shows that reptiles and amphibians cause around 74,000 Salmonella infections every year in the US.
Investigators stressed the importance of washing animal habitats outside to avoid contaminating the kitchen sink, and washing hands with soap and warm water and using hand sanitiser after exposure to the animal or its habitat.
The authors advised that pet shops should do more to inform consumers on safety and hygiene, and to help them understand that they didn't have to handle the animal directly in order to pick up an infection - contact with the aquarium water was enough.
The research by the the US Centers for Disease Control and Prevention (CDC) was published in Pediatrics and it is the first to report a nationwide Salmonella outbreak associated with amphibians.
Last year a city in Canada banned the keeping of African dwarf frogs by both retailers and consumers. Councillors in Markham, Ontario decided that the health risks associated with keeping them as pets was just too great, although people who already owned them would be allowed to keep them until the frogs die.
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