SHANGHAI, May 11 -- Chinese veterinary officials yesterday announced the development of a brand new diagnostic reagent and vaccine, which they claim can help end an outbreak of a deadly pig disease in the south of the country.

The Ministry of Agriculture said in a statement that a mass immunization of pigs would be completed as early as possible because imminent high summer temperatures and humidity could help spread the blue ear disease.

The disease - officially named porcine reproductive and respiratory syndrome - does not affect humans and is listed by the government as one of the 61 class II animal epidemic diseases that must be brought under immediate control.

The vaccine invented by the Chinese Center of Animal Disease Control and Prevention and the China Institute of Veterinary Drug Control would see its first use in the epidemic-stricken Guangdong Province.

"We will speed up the production and distribution of vaccines and simultaneously tighten quality supervision," the ministry said.

The ministry required veterinary departments to stay on high alert for the disease and immediately report suspect cases.

"Once the virus mutates, it will become more pathogenic and more difficult to cure," it warned.

A major problem was the poor breeding conditions as most farmers tend to raise their pigs in open places and pens are poorly equipped with anti-epidemic measures.

The frequent transportation of live pigs might also facilitate the spread of the disease, it said. A nationwide survey would be carried out to ensure preventive measures and emergency action plans were implemented in counties and townships.

Chinese epidemiologists said the disease arrived in China in the mid-1990s and the latest outbreak in Silao Town of Yunfu City was caused by a deadly mutation of the virus.

More than 300 pigs died after they stopped eating, became feverish and started hemorrhaging at the end of April.

According to the Yunfu government, the infected pigs were raised by individual rural households rather than on industrial pig farms and were not exported overseas.

The government said it had delivered two reports to the World Organization for Animal Health and the UN Food and Agriculture Organization.