BEIJING: China's Ministry of Agriculture and Rural Affairs said on Monday it will crack down further on illegal production and sales of African swine fever vaccines in a sign of the extent of a problem that is damaging the world's largest pig industry.

The ministry, which has been warning against such behaviour since 2019, said tougher measures were needed to "prevent hidden risks caused by fake African swine fever vaccines, and make every effort to maintain the overall situation of the recovery of pig production and the stable development of the industry".

Industry insiders believe that use of illicit vaccines have caused a new, chronic form of African swine fever, Reuters reported in January, which causes a debilitating condition that can lower output of hogs.

China's hog herd is still recovering from a devastating outbreak of the disease, which in its original form was almost always deadly to pigs, and wiped out about half of the herd.

Analysts and industry insiders say a resurgence of the disease over the winter has slowed the recovery of pig production.

The ministry said identification and testing must be strengthened, and urged local governments to identify any positive samples of the virus, reporting any strains with artificial gene deletions to provincial veterinary authorities as soon as possible.

No vaccine against the disease has been approved anywhere in the world but strains of the live virus with deleted genes thought to protect against the disease are believed by industry to be circulating in China.