The dogs are transported in horrible conditions and suffer from all sort of diseases like Parvo and Distemper. They often have broken bones and have to travel in tiny cages next to dogs that are already dead. Even pigs in China are transported in better conditions It is a completely unregulated market.
No sanitary conditions in slaughterhouses or meat processing, no testing for illnesses, viruses and bacteria that could affect humans. In fact, meat trade is still one of the biggest contributors to rabies in Asia (China is the second largest rabies hotspot in the world and cases have been increasing over the last 10 years).
Finally, as if it wasn't enough to transport them in horrible conditions, dogs are tortured before killing them and sometimes are skinned alive as people think this makes meat taste better.