Amphibians cause of human Salmonella Typhimurium multi-state outbreak

VANCOUVER — African dwarf frogs were found to be the cause of the first multi-state outbreak of Salmonella Typhimurium in children, according to results from a matched case-control study presented by Shauna L. Metee, RN, MSN, MPH.

Metee, of the CDC, and colleagues identified 113 cases of S. Typhimurium in children with a median age of 4 years residing in 31 states during April 2009 and March 2010. Thirty-five percent of cases were hospitalized and no deaths occurred.

For the study, researchers compared cases of S.Typhimurium with a group of controls with recent Salmonella infection caused by strains other than S. Typhimurium. Illness was significantly associated with frog exposure in 67% of cases and 3% of controls. Of the 21 patients aware of the type of frog with which they had been in contact, 95% reported contact with the African dwarf frog.

Moreover, of those who reported contact with frogs, 30% had touched frogs; 41% fed the frogs; 61% had contact with the frog’s habitat; and 64% had contact with the frog’s water, which amplifies the Salmonella virus, according to Metee.

The origin of the infected frogs was found to be a breeder’s facility in California, where between 800,000 to 1 million frogs were observed in close quarters. Samples were pooled from the water filtration systems, water from frog tanks, cleaning tools, floor drains and the frogs themselves. All of the frogs were found to carry the same strain of S. Typhimurium.

Although only African dwarf frogs were implicated in this outbreak, other studies have shown that additional species of frogs could also be Salmonella carriers. As a result, the CDC recommends that “consumers consider all aquatic frogs and all the water in the [frogs’] habitat contaminated,” said Metee.

The CDC offers the following additional recommendations to physicians and those handling African dwarf frogs and other amphibians:

Increase awareness of Salmonella infection in frogs.
Wash hands thoroughly after handling the frogs, their habitats and any water with which the frogs might have come into contact.
Keep habitats away from food-preparation areas and places where small children explore such as cribs, playpens and diaper areas.
Children younger than 5 years, the elderly and the immunocompromised should avoid all contact with these frogs and keep them out of the home.

PERSPECTIVE

We have concerns about the fact that amphibians and reptiles do carry Salmonella and they don’t look like they’re sick. It’s not uncommon for us to hear a story of an infant who has a Salmonella infection and the health department asks : ‘Is there a reptile in the house?’ and they’ll find out that the father has an iguana. The family will say that the child never even goes in the room where the iguana is, but somehow the environment to which that infant is exposed is contaminated with the Salmonella from the reptile; maybe from an adult’s hands; or maybe the reptile crawls on the floor and then so does the baby — we don’t know exactly how it happens. But that’s why we strongly recommend that anyone whose immune system is not really strong — that would include infants and very elderly persons — not be in a home with a reptile or amphibian.

– Patricia M. Griffin, MD
Chief, Enteric Diseases Epidemiology Branch,Division of Foodborne,
Waterborne, and Environmental Diseases,National Center for Emerging and Zoonotic Infectious Diseases, CDC

Metee SL. #798. Presented at: the IDSA 48th Annual Meeting; Oct. 21-24, 2010; Vancouver, B.C.