The rotting bodies of about 6,000 pigs in a river that supplies tap water to Shanghai has drawn attention to an ugly truth – China’s pig farms are often riddled with disease and one way or another, sick animals often end up in the food chain.

Authorities have found traces of a common pig virus in some of the animals floating in the Huangpu River this week, and industry insiders say farmers likely dumped them, common in an industry which has no system of compensation for losses from disease.

“There is no mechanism by which, whenever diseases are found among pigs, the Government compensates pig breeders so as to control the spread of diseases or compensate pig breeders for losses,” said Feng Yonghui, general manager at pig-industry research organisation Soozhu.com.

To make matters worse, Feng said insurance companies were unwilling to insure pig breeders because the risks were so high.

On Wednesday, workers on barges and on the riverbank used pitchforks to drag bloated dead pigs out of the river.

Pork is China’s staple meat and the swine population is the world’s largest at 475 million head at the end of last year.

At market, margins on pork are thin and for hog farmers unwilling to spend money to incinerate or bury dead animals, the Huangpu River may have offered a tempting alternative.

While there was no proof any sick animals had been butchered and sold for meat in this case, media have reported several scandals involving sick or dead livestock being butchered and sold for meat.

Early this year, state media accused a supplier of chicken to KFC and McDonald’s of selling them sick poultry. The supplier denied it.

While authorities have not confirmed a disease, or the death of unusually large numbers of pigs, talk of pigs dying would seem to suggest an outbreak of some sort.