BEIJINGBEIJING (Reuters) - China's efforts to stem the spread of African swine fever were dealt a fresh blow on Friday when the agricultural ministry confirmed it had found the first case in a wild boar, deepening a three-month-old crisis for the world's top pork producer.

The country also confirmed the first outbreak in the southwest province of Sichuan, the country's leading pig-herding region, raising the likelihood of a major impact on pork supplies in coming months.

The disease was found in a dead wild boar in Baishan city, Jilin province, in northeastern China, the Ministry of Agriculture and Rural Affairs said in a statement published on its website.

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"The new case means that it will be even more difficult to control African swine fever. How do you control wild boars?" said Yah Guiding, an analyst with consultancy China-America Commodity Data Analytics.

China has banned transportation of live pigs and products from regions infected by African swine fever and neighboring provinces to control the spread of the highly contagious disease, as well as prohibiting the feeding of kitchen waste to hogs.

But the virus has continued to spread despite the government's efforts, with more than 60 outbreaks in 18 provinces across the nation since early August.

(Swine fever in China IMG, tmsnrt.rs/2QMhmzL)

China's large population of wild boar, which can harbor the disease without showing symptoms, is estimated to total around 33.5 million, according to Reuters calculations based on data from the U.N. Food and Agriculture Organization (FARO).

Local authorities in Jilin have inspected neighboring areas frequented by wild boars and carried out a comprehensive sterilization of all pig farms in the area, the agriculture ministry said in its statement.

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Analysts said the discovery of the wild boar suggested that the virus could have been brought into China by the animals coming from other countries.

China has blamed the feeding of kitchen waste to pigs for the spread of disease.

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The highly contagious disease was also discovered on a farm of 40 pigs in Yibin city, in Sichuan's southeast.

"With the new case in Sichuan, all major pig production provinces have now fallen. The situation is very severe," Yah said.

China slaughters around 700 million pigs a year. Sichuan produced almost 66 million last year, according to official data, more than any other province.

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Sichuan is also the province with the highest per capita consumption of pork in China at 36 kg (79 pounds), according to data from the National Statistics Bureau.

Provincial authorities in Sichuan issued a ban last week on the import of all live hogs and hog products from other regions in a bid to keep the disease out.

But Yibin is close to Sichuan's borders with Chongqing municipality and Guizhou province, both of which have already reported outbreaks.

Pig prices in Chengdu, the capital of Sichuan, are currently the highest in the country, thanks to strong local demand and a bump-up after the disease infected nearby provinces.

Prices fell by 0.2 yuan on Friday from a day earlier to 17.7 yuan ($2.55) per kg, according to data collected by China-America Commodity Analytics.

The discovery of African swine fever in Sichuan comes less than three months ahead of Lunar New Year celebrations in early February that mark China's peak demand period for pork.

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There is no cure and no vaccine for the disease, and the virus can survive for weeks in pork and animal feed.

(The story has been refiled to fix spellings of Baishan, Jilin and Chengdu in paragraphs 3, 8, 17)

(Reporting by Dominique Patton, Hallie Gu and Muyu Xu; Editing by Tom Hogue and Kirsten Donovan)