Companion Animals and Human Health: Part II -- Zoonotic Diseases: Salmonella

Salmonella

Epidemiology

There are almost 2000 serotypes of the Salmonella genus found in the environment, wild and domestic animals, and humans. Normally associated with contaminated food, the disease is often transmitted via hand-to-mouth contact from either ill or asymptomatic individuals or animals, their bedding, surfaces they have contaminated, or water they have contaminated. A number of species kept as pets have been associated with human Salmonella infections.^[4]

Turtle. The frequency of salmonellosis associated with baby turtles sold as pets led the US Food and Drug Administration (FDA) to ban the sale of pet turtles with shells less than 4 inches long beginning in 1975. Recently, the FDA issued a press release re-emphasizing the risk presented by pet turtles to their owners after a 4-week-old Florida infant died of an infection caused by Salmonella pomona.^[5] The organism was also found in a pet turtle in the infant's home. Other reptile pets and Salmonella organisms frequently associated with them are:^[6]

• Iguanas -- Salmonella marina; and
  
  
• Turtles and lizards -- Salmonella java and Salmonella poona.

Baby chicks. A recent Centers for Disease Control and Prevention (CDC) publication cited the ongoing problem of human Salmonella outbreaks associated with the sale of baby chicks to the public in agricultural feed stores.^[7] Purchasers are generally unaware of the potential for these chicks to be Salmonella carriers and do not take adequate hygiene precautions to prevent fecal-oral transmission. While these chicks are cute and are sometimes purchased as pets, they pose a significant risk for Salmonella infections.

Rodents. In 2004, hamsters, mice, and rats (sold both as pets and to feed snakes) were found to be infected with multidrug-resistant Salmonellatyphimurium in a multistate outbreak associated with a number of pet rodent breeders.^[8] It was determined that a number of the breeders were routinely providing antibiotics for nonspecific rodent enteritis either through feed or water. Cases occurred in 10 states and involved 17 humans.

Dogs and cats. Dogs and cats with clinical infection may exhibit:

• Gastroenteritis;
  
  
• Bacteremia; and
  
  
• Enterotoxemia.

They may serve as asymptomatic carriers and have contaminated:

• Fur;
  
  
• Fecal material; and
  
  
• Saliva.

Dogs and cats may become infected through contact with wild rodents or through contaminated diet or treats provided by humans.^[9] The current trend for "natural diets" has led some owners to provide their dogs with a "bones and raw food diet (BARF)." The diet often consists of whole raw chicken mixed with vegetables. A recent study found that 80% of dogs fed this diet shed Salmonella in their stool.^[10] Another source of Salmonella for dogs and, subsequently, human infections has been processed pig ear treats.^[11]

Incidence

The CDC estimates that there are 40,000 cases of salmonellosis in the United States every year, but there is major underreporting because many of the milder cases are not identified or reported.^[12] They also estimate that 600 individuals die yearly.

Pathology and Symptoms

Ingested Salmonella organisms enter the gastrointestinal tract, access the bloodstream via the lymphatic channels, and cause:

• Diarrhea;
  
  
• Fever; and
  
  
• Abdominal cramps.

Diagnosis

Diagnosis is made from isolation of Salmonella organisms in cultures from:^[13]

• Feces;
  
  
• Blood;
  
  
• Urine;
  
  
• Pus; and
  
  
• Vomitus.

Treatment

Salmonella infections normally resolve without treatment in 5 to 7 days. Patients with severe diarrhea may require intravenous (IV) fluids. Antibiotics:

• Do not shorten the duration of symptoms;
  
  
• May prolong the duration of bacterial carriage; and
  
  
• Are not routinely used to treat uncomplicated nontyphoidal Salmonella gastroenteritis.

If the infection spreads from the intestines, it can be treated with:^[14]

• Ampicillin;
  
  
• Gentamicin;
  
  
• Trimethoprim/sulfamethoxazole; or
  
  
• Ciprofloxacin.

Prevention

Prevention of companion animal-associated Salmonella infections is based primarily on good hygiene practices. Good hand-washing is essential after handling the animal, its housing, and the bedding of cage-raised animals. A number of different Internet sites and publications are available to assist the pet owner in preventing Salmonella, Campylobacter, or other intestinal infections. The CDC Web site has excellent instructions on how to maintain a reptile pet in the home safely. These same instructions can be used for other cage-confined animals.^[15]