SHANGHAI - China's largest city is setting a limit of one dog per family in an effort to gain control over the soaring pet population and curb rabies.

Cao Yi already was walking her dogs at 11 p.m., hoping to avoid trouble both with neighbors and with the authorities over her brown poodle and golden retriever.

"I'm afraid one of the dogs might be taken away," she said.

The rule that takes effect today means either finding a new home for one of her pets or registering one with her parents.

Shanghai's new pet ownership rules also slash steep fees for dog registration - in hopes of bringing more undocumented dogs onto the books - and require those walking dogs to keep them on leashes.

Only about 140,000 of Shanghai's estimated 800,000 dogs have been registered under current rules, which require payment the equivalent of a $300 fee every year for those living downtown and half that for those in the suburbs.

Under the new rules, annual fees drop to about $75 for downtown residents, about $45 for those in suburbs, and $13 for rural residents. Rabies shots cost another $6 for domestic vaccines or $9 for imported ones.

Beijing and the southern city of Guangzhou have similar regulations to control rabies.

For some middle-class Chinese, the canine controls are an unwelcome intrusion into their private lives, and a reminder of extremist political campaigns in decades past, when pet keeping was deemed an anti-communist, bourgeoisie luxury.

Whether the lower costs will induce more Shanghainese to legalize unregistered pets or really get rid of those above the quota remains to be seen.

These days, the city still conducts occasional roundups of unregistered dogs. Indoor pets, like birds or cats, don't require registration but cities want to keep track of dogs because they are more likely to go outside, where they can form wild packs and spread disease.

Occasional mass outbreaks of rabies - mainly in the provinces - have prompted culls of tens of thousands of dogs, and sometimes protests from angry pet owners. But in most cases opposition takes the form of passive resistance; some Shanghai residents just send their dogs to stay with friends or relatives until it seems safe to bring them home.

"Some of my friends from the dog lovers club say they don't want to register their pets because they don't take them outside, to keep them clean," said Cao.

While pedigreed animals can cost thousands of dollars, inexpensive breeds can be easily bought without any enforcement of requirements for annual rabies' vaccines. Many first-time pet owners don't bother to spay or neuter their animals and eventually abandon them when they grow tired of the burdens of keeping an animal. Bands of strays can be seen in the city's suburbs.

A recent pet population explosion has brought on a spike in rabies infections. About 2,500 people die of the disease each year in China. In big, crowded cities like Shanghai, home to 23 million people, police say they handle thousands of complaints over dog bites each year.

Wang Ruimei, a retired hospital worker, says she had to pay $300 to get her huge black dog back after it ran away several years ago when spooked by firecrackers and was seized by animal control authorities.

"At first we decided to forget about it, but then we missed him too much. It's a lot of fun having a dog for company, sometimes better than some people," Wang said. "But one dog is enough."

Ada Xu, a 35-year-old office worker, already was paying the required fees for her beloved "Tata," a brown Pekinese.

"It's expensive, but I can afford it. And anyway I don't care whether or not I can have another dog," she said.

Not all Shanghainese are dog lovers, and for Yang Wei, who has found herself stuck in situations where a dog was blocking her way, the prospect of more vigorous enforcement of leash laws is welcome.