Got a baby or a toddler in the house? Time to get rid of that iguana.

Pet reptiles--including all types of lizards, snakes and turtles--can be a source of life-threatening infections and do not belong in households that have children under the age of 5, according to a recommendation issued last week by the federal Centers for Disease Control and Prevention (CDC).

Reptiles also shouldn't be handled by small children or by anyone whose immune system doesn't work well, the agency cautioned last week. In addition, the animals should not be kept as pets in preschools and day care centers.

With the growing popularity of snakes and lizards as pets, health officials are concerned about a recent increase in reptile-related salmonella infections. Although most cases of salmonella are caused by food contamination, reptiles account for about 93,000 cases of such illness each year, or about 7 percent of the total.

Many people are aware that turtles can carry salmonella bacteria--in fact, the sale of small turtles as pets was banned for that reason in 1975--but most consumers and even many pet store owners apparently don't know that lizards and snakes can be carriers, too.

Salmonella infections can cause fever, vomiting, bloody diarrhea and sometimes blood poisoning, meningitis or death.

People can become infected by handling the animal or by handling objects contaminated with the reptile's feces. Touching the reptile isn't necessary. According to the CDC, some cases of reptile-associated illness have occurred in infants who never even touched the scaly family pet, presumably resulting from having been held by people whose hands were contaminated.

Reptiles carry salmonella in their digestive tracts and frequently shed the bacteria in their feces. The microbes don't make them sick. There is no reliable test or treatment to ensure that a pet reptile won't carry the bacteria. "You can test it one week and it will be negative, two weeks later and it will be positive," said Stephanie Wong, a veterinarian with the CDC's food-borne and diarrheal diseases branch. "We feel there is no way to say that a reptile is salmonella-free."

Wong said CDC officials are so concerned about the risk to young children that they decided last week to strengthen one of the new guidelines after it had already been printed in the agency's weekly bulletin. Originally, the recommendation had said that reptiles should not be kept in households with children less than a year old; this was revised to include households with children under the age of 5.

Among the cases of illness reported by the CDC:

* A 5-month-old baby died suddenly last year in his Wisconsin home. An autopsy revealed no cause, but bacterial cultures of a blood sample taken from the heart were positive for a rare type of salmonella associated with reptiles. Bacterial cultures of the droppings of the family's pet iguana yielded the same bacteria.

* In 1997, two brothers living in Kansas, aged 6 and 3, developed fever, cramps, vomiting and bloody diarrhea and were treated with antibiotics. They shared a room with two pet corn snakes that they handled regularly. Stool cultures from both the boys and the snakes grew the same species of bacteria, Salmonella typhimurium.

* An 8-year-old Massachusetts boy with an inherited immune system disorder developed vomiting, abdominal cramps, bloody diarrhea and headaches in 1997. A stool culture was positive for salmonella. Three days earlier, his family had bought two iguanas, and the child had been putting the new pets on his head and face.

About 3 percent of U.S. households have reptiles, according to a CDC estimate based in part on an industry survey. "They're becoming more common household pets," Wong said.

The symptoms of salmonella infection--typically abdominal cramps, diarrhea, fever and sometimes vomiting or headaches--begin 24 to 72 hours after exposure. Severe cases are treated with antibiotics. But such drugs usually aren't necessary in mild cases of illness, Wong said, and their use is discouraged because they may promote the emergence of resistant strains of bacteria. For the same reason, she added, "we don't encourage people to take their reptiles to the vet and treat them with antibiotics."

Currently, two states (including Maryland) require pet dealers to inform people purchasing reptiles about the risk of salmonella infections. The CDC is encouraging other states to adopt similar requirements and, if such measures prove unsuccessful, to consider restricting the sale of reptiles.

Might other exotic pets pose a similar risk of infection? Currently, CDC researchers are training their microscopes on amphibians such as frogs, toads, newts and salamanders. At least one scientific study reports that amphibians tested in the wild can carry salmonella.

"We don't have case reports or histories of persons becoming ill from amphibians," Wong said. "We're sort of keeping our eye out."

Playing It Safe

To help prevent the transmission of salmonella from reptiles to humans, the CDC recommends:

* Pet stores, veterinarians and pediatricians inform owners and potential owners of reptiles about the risk of salmonella infection.

* People always wash their hands thoroughly with soap and water after handling reptiles or reptile cages.

* Children, people with compromised immune systems and others at increased risk for infection or serious complications of a salmonella infection avoid contact with reptiles.

* Pet reptiles be kept out of households with children under the age of 5 and with anyone with a compromised immune system. Families expecting a new child should remove the pet reptile before the infant arrives.

* Pet reptiles not be kept in child care centers.

* Pet reptiles not be allowed to roam freely throughout a home.

* Pet reptiles be kept out of kitchens and other food preparation areas. Kitchen sinks should not be used to bathe reptiles or to wash their dishes, cages or aquariums. If bathtubs are used, they should be cleaned thoroughly and disinfected with bleach.