These puppy mills keep their dogs in cruel conditions, cramping the animals together in wire cages, not feeding them, allowing their water and living quarters to become dirty. Mothers are treated as breeding machines, forced to produce pups at an unnatural rate only to be abandoned when they are no longer fertile.

What's worse, repeated inbreeding to obtain rare traits results in many animals with defects, especially Japanese dogs.

While a mini-poodle that fits into a purse looks healthy and bouncy, it may have several genetically defective siblings, born without paws or eyes, that will never be seen. Experts say four times as many Japanese puppies are born with defects than those in western countries.

Puppy mills are banned in many countries, but just like many other illegal and profitable trades, there is no way to eradicate them while consumers still buy puppies.

The internet has offered new possibilities for illegal pet traders.

Hong Kong Police arrested several people who operated an unlicensed online pet shop selling puppies produced on the mainland.

In some cases pet traders pose as pet owners on the net, claiming they are compelled to abandon their pets and are looking for responsible owners. They say they will give away the purebred pets - actually bred on the mainland - for free. Then they ask unsuspecting buyers to reimburse them for medical and other expenses.

Caveat emptor!