The fright of the iguana: pet reptiles pose risk of salmonella infection for their owners

A 6-week-old boy in Ohio was hospitalized with diarrhea, stiff neck, and fever. He was treated and released from the hospital after 56 days.

Vomiting, bloody diarrhea, and fever put a 3-week-old Pennsylvania girl in the hospital. She was treated with penicillin and discharged 11 days later.

A 5-month-old girl in New Jersey was hospitalized because of vomiting, lethargy and fever. She was treated and allowed to return home after 10 days.

Besides some of their symptoms, what did all three infants have in common? Each tested positive for salmonella bacteria, and all had exposure to a reptile.

Approximately 3 percent of American households own an estimated 7.3 million reptiles, according to the Pet Industry Joint Advisory Council. Because the most popular species will not breed if closely confined, most reptiles are captured in the wild or hatched at reptile ranches and imported. The number of reptiles imported into the United States has increased dramatically from 27,806 in 1986 to 798,405 in 1993, as reported by the U.S. Fish and Wildlife Service, and the majority are iguanas.

But what many animal lovers don't know is that with these imported pets come exotic forms of salmonella bacteria that can cause life-threatening illness in humans.

"Many parents do not know that owning an iguana puts their children at risk for salmonella infection," say researchers from the national Centers for Disease Control and Prevention in Atlanta. Even in homes where young children and infants are not permitted to touch or come in contact with the animals, they may still become infected, according to a study published in the March 1997 issue of the Journal of Pediatrics.

What Is Salmonella?

Salmonella is the genus name of a number of bacteria commonly associated with food poisoning from contaminated or undercooked foods, and salmonellosis is the disease the bacteria can cause. In food-related cases, most people suffer from gastroenteritis, often experiencing vomiting, fever, diarrhea, and cramps. For high-risk individuals, such as those with weakened immune systems, those taking antibiotics, pregnant women, the elderly, and children under 5, salmonellosis may be even more devastating, leading to blood infections, meningitis, abortion, and death.

In a case reported by the New York Health Department in 1995, a pregnant woman with fever and diarrhea went into preterm labor and delivered a baby who died 12 hours later. Follow-up blood samples of mother and child, in conjunction with samples from the family's pet iguana, tested positive for the salmonella strain associated with reptiles.

"Like most other reptiles, iguanas carry salmonella in their intestinal tracts," says Patrick L. McDonough, Ph.D., assistant director of bacteriology at Cornell University's College of Veterinary Medicine in New York. "The bacteria are `shed' periodically in the animals' feces, and that's how the bacteria gets on the animals' skin, their cages, and other materials they touch."

An influx of cases at Cornell University since 1993 has prompted officials to warn owners that good hygiene is essential to prevent the spread of salmonella.

"Wash your hands with warm, soapy water immediately after handling iguanas or their cage litter, and before touching food or anyone else," McDonough says. He adds that while researchers once believed salmonellosis was transmitted primarily through direct contact with reptiles, it is now known that the bacteria need only be present on surfaces or on the hands of others to infect individuals indirectly.

In one such case, 20 patients were diagnosed with the disease within eight days of visiting a Komodo dragon exhibit at a Colorado zoo. According to Joseph Madden, Ph.D., strategic manager for microbiology at FDA's Center for Food Safety and Applied Nutrition, zoo officials believe that the dragons had, while being moved to their cages, licked several handrails at the zoo, and those areas were then touched by zoo visitors who subsequently ate lunch without washing their hands.

An Outbreak Revisited

In the early 1970s, FDA banned the distribution and sale of baby turtles with shells 4 inches in length or less after a quarter million infants and small children were diagnosed with having turtle-associated salmonellosis. The agency believed that turtles larger than 4 inches did not pose the same threat since youngsters would not likely try to fit them into their mouths. CDC estimated that in 1973, pet turtles accounted for 14 percent of the salmonella-caused illnesses in the United States.

But the FDA-imposed ban allows for some exceptions. Turtles still can be exported to other countries and sold to experts for bona fide scientific, educational and exhibition purposes. Selling turtles to pet stores is not considered a bona fide purpose.

Janet McDonald, a public affairs specialist with FDA's San Francisco district office, believes that since the turtle issue is so old, people have forgotten that they are still illegal in the United States.