OCEANSIDE - Those tiny red-eared slider turtles for sale for a few bucks outside local stores might seem like the perfect gift for your budding biologist, but most are illegal and can carry disease.

Turtles are potential carriers of salmonella, a naturally occurring bacteria in turtles and other reptiles, said Julie Bank, executive director of the North County Humane Society.

The bacteria can cause diarrhea, stomach pain, nausea, vomiting, fever and headache. The risk is highest for children, seniors, pregnant women and people with weak immune systems.

That's where the cute factor comes in. Handling the silver dollar-sized red-eared sliders, which are green with red "ears," is tempting for young and old.Most adults know not to put the reptile in their mouths - but that's precisely the way most small children experience the world. Health officials in North Carolina recently linked five cases of salmonellosis in children to handling turtles.

"So the warning is: They are not necessarily the healthiest animal, and your kids can get sick," Bank said.

Beyond the health risk, selling red-eared slider turtles smaller than four inches is a federal crime, Bank said. The law's logic: Larger turtles aren't so cuddly, and kids are less likely to put a four-inch turtle in their mouths, Bank said.

Red-eared sliders are one of the most popular pet turtles, said Joe Alvarez of LLL Reptile and Supply in Escondido on Christmas Eve. Alvarez said his store was temporarily out of the turtles. PetSmart in Oceanside was also out of stock on Monday.

Contact staff writer Philip K. Ireland at (760) 901-4043 or online at pireland@nctimes.com.