Investigation Update: Outbreak of Human Salmonella Typhimurium Infections Associated with Contact with Water Frogs

Update for December 21, 2009

CDC is collaborating with public health officials in many states to investigate a multistate outbreak of human Salmonella serotype Typhimurium infections due to contact with water frogs including African Dwarf Frogs. Water frogs commonly live in aquariums or fish tanks. Amphibians such as frogs and reptiles such as turtles, are recognized as a source of human Salmonella infections. In the course of routine assessment, a number of cases with the same strain have been identified over many months.

New information in the investigation indicates the outbreak likely began in April, which is earlier than previously reported. An additional 26 ill persons infected with the outbreak strain between April and July have been identified and are now included in the overall number of reported individuals infected.Only four new recent illnesses have been reported since the previous web update on December 16. Investigations are still ongoing to see if the outbreak may have been occurring prior to April.

As of 9:00pm EST on December 21, 2009, 83 individuals infected with the outbreak strain of Salmonella Typhimurium have been reported from 31 states. The number of ill persons identified in each state is as follows: Alabama (1), Arizona (1), California (4), Colorado (4), Florida (1), Georgia (1), Idaho (1), Illinois (5), Indiana (1), Kentucky (1), Louisiana (1), Massachusetts (3), Maryland (2), Michigan (4), Minnesota (1), Missouri (4), Mississippi (1), Nebraska (1), New Jersey (2), New Mexico (1), New York (2), Nevada (1), Ohio (2), Pennsylvania (4), South Dakota (3), Tennessee (3), Texas (4), Utah (13), Virginia (3), Washington (7) and Wisconsin (1).

Among the persons with reported dates available, illnesses began between May 24 and November 16, 2009. Infected individuals range in age from < 1 year old to 54 years old. Eighty percent (80%) of patients are younger than 10 years old and the median age is 4 years. Forty-nine percent (49%) of patients are female. Among the 45 patients with available information, 16 (36%) were hospitalized. No deaths have been reported.

Investigation of the Outbreak

In an epidemiologic study, ill persons answered questions about contact with animals and foods consumed during the days before becoming ill and investigators compared their responses to those of persons of similar age and gender previously reported to State Health Departments with other illnesses. Preliminary analysis of this study suggests contact with frogs, including water frogs such as African Dwarf Frogs, is a likely source of the infections. In addition, environmental samples taken from aquariums containing aquatic frogs in three homes of ill persons have yielded isolates of Salmonella Typhimurium matching the outbreak strain.

Advice to Consumers

• Always wash hands thoroughly with soap and water after touching any amphibian (e.g., frog) or reptile (e.g, turtle), their housing, or anything (for example, food) that comes in contact with them or their housing.   Adults should assist young children with hand washing.  
• Watch for symptoms of Salmonella infection, such as diarrhea, fever, and abdominal cramps.  Call your health care provider if you or a family member have any of these symptoms.

Persons who should avoid contact with amphibians and reptiles and their habitats (e.g., aquarium, fish tank, or terrarium)

• Persons at increased risk for serious infection from salmonellosis are children < 5 years old, elderly persons, and persons with weakened immune systems.
• These persons should avoid contact with amphibians (e.g., frogs) and reptiles (e.g., turtles) and anything that comes in contact with them (e.g., aquarium, habitat, and water).
• Keep amphibians and reptiles out of homes with children < 5 years old or people with weakened immune systems.

Placement and maintenance of habitats

• Amphibians (e.g., frogs) and reptiles (e.g., turtles) should not be kept in child-care centers.
• Habitats containing amphibians or reptiles should not be kept in a child’s bedroom, especially children aged < 5 years.
• Do not allow amphibians or reptiles to roam freely through the house, especially in food preparation areas.
• Keep amphibians and reptiles out of kitchens and other areas where food and drink is prepared or served to prevent contamination.
• Habitats and their contents should be carefully cleaned outside of the home. Use disposable gloves when cleaning and do not dispose of water in sinks used for food preparation or for obtaining drinking water.
• Do not bathe animals or their habitats in your kitchen sink. If bathtubs are used for these purposes, they should be thoroughly cleaned afterward. Use bleach to disinfect a tub or other place where reptile or amphibian habitats are cleaned.
• Children aged <5 years should not clean habitats.
• Always wash hands thoroughly with soap and water after cleaning habitats.

Advice to Pet Store Owners and Others Who Sell or Display Amphibians and Reptiles

• Pet store owners and others who sell or display amphibians (e.g., frogs) and reptiles (e.g., turtles) should provide information to owners and potential purchasers of amphibians and reptiles about the risks of acquiring salmonellosis from these animals.
• More information on displaying animals in public settings can be found in the 2009 Compendium of Measures to Prevent Diseases Associated with Animals in Public Settings.

Advice to Health Care Providers

• Health care providers should question patients on pet and animal ownership and should provide education about the risks of acquiring salmonellosis from amphibians (e.g., frogs) and reptiles (e.g., turtles).
• Health care providers should advise patients on proper hand washing practices.

Advice to Veterinarians

• Veterinarians should provide education to amphibian and reptile owners about the risks of acquiring salmonellosis from these animals.
• Veterinarians should provide education to amphibian and reptile owners on how to properly clean the animal habitat.

Clinical Features/Signs and Symptoms

Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12–72 hours after infection. Infection is usually diagnosed by culture of a stool sample. The illness usually lasts from 4 to 7 days. Although most people recover without treatment, severe infections may occur. Infants, elderly persons, and those with weakened immune systems are more likely than others to develop severe illness. When severe infection occurs, Salmonella may spread from the intestines to the bloodstream and then to other body sites and can cause death unless the person is treated promptly with antibiotics.

More general information about Salmonella can be found here under Salmonella FAQs.

Additional Resources

• Podcast - CDC Kidtastics: "Water Frogs, Aquariums and Salmonella - Oh My!"
• US Food and Drug Administration Center for Veterinary Medicine - FDA Reminds Public that Frogs Carry Salmonella

Previous Updates

• December 16, 2009
• December 10, 2009
• December 7, 2009