NANNING - China's livestock industry, vital to the nation's food security, has become a growing pollution and public health headache in some rural areas.

In Santang Township in South China's Guangxi Zhuang autonomous region, farmers simply dump the carcasses of their animals without any treatment, according to Liu, a local villager.

"If the number of dead animals is big, we usually dump the carcasses in remote places away from rivers to prevent disease," Liu said, adding that there are no decontamination facilities in his village.

The Animal Epidemic Prevention Law says that animals which die of disease on farms must be burned at appointed treatment stations. However,in many places such facilities are outmoded and unfit for purpose.

Pigs may float

Fang Huansen, head of animal health supervision in Ningming County of Guangxi, said that carcasses thrown into ponds or rivers could seriously pollute the water, making it highly injurious if consumed.

Carcasses are often dumped to reservoirs of disease and could cause epidemics or transmit infections to both animals and humans.

He Ruogang, professor of animal science and technology at Guangxi University, believes the problem is not just illegal dumping, but lack of supervision means diseased meat often makes it onto the market.

"Profits on meat are high, as are the costs of treating fallen stock, so some greedy farmers sell the carcasses at very low prices to processors who sell it on the market," He said.

Guangxi is only a snapshot of a bigger picture. As livestock breeding goes industrial, it brings serious environmental worries.

In March, the rotting bodies of nearly 6,000 pigs were found in a river that provides 22 percent of Shanghai's tap water, causing panic in China and international scorn.

Despite authorities' protestations that the river was not contaminated and Shanghai's tap water was safe, laboratory tests found porcine circovirus in one water sample. The virus is spread among pigs though not transmissible to human beings.

The source of the dead pigs remained a mystery until a hog farm in Jiaxing city in neighboring Zhejiang province, confessed on March 13. Jiaxing authorities said 70,000 pigs had died this year from climate conditions and changes to farming techniques.

On the same day, a court in Wenling city, also in Zhejiang, sentenced 46 people to prison terms ranging from six months to six and a half years for processing and selling pork from diseased pigs from 2010 to 2012. Wenling's pork safety campaign, which began in April last year, has meant the seizure of more than 6 tons of pork products that tested positive for various viruses.