SEOUL, Korea, Republic Of -- South Korea said Wednesday North Korea has so far ignored its calls for joint efforts to stem the spread of highly contagious African swine fever following an outbreak near North Korea's border with China.

South Korea's agricultural ministry on Wednesday said that blood tests of pigs from some 340 farms near the inter-Korean border conducted through Tuesday came back negative. Hundreds of fences and traps have been installed around the farms to prevent pigs from being infected by wild boars that roam in and out of North Korea.

But the lack of bilateral co-operation renders South Korea helpless in preventing the disease from reaching North Korean farms near the border. There's concern that an outbreak in South Korea would deal a significant blow to a massive industry that involves 6,300 farms raising more than 11 million pigs.

South Korea's Unification Ministry, which deals with inter-Korean affairs, said the North hasn't responded to proposals for joint quarantine efforts since it reported an outbreak near its border with China to the World Organization for Animal Health, or the OIE, last week. The North said 77 of the 99 pigs at the co-operative farm in Jagang province died of the disease and the remaining 22 pigs were culled.

The outbreak comes as the North has significantly slowed its engagement with South Korea following the collapse of a February summit between North Korean leader Kim Jong Un and President Donald Trump over disagreements for sanctions relief in exchange for North Korea's nuclear disarmament.

The disease, which has decimated pig herds in China and other Asian countries, is harmless to humans but for pigs is fatal and highly contagious. There is no known cure or vaccine.

North Korean state media in recent weeks have published several articles detailing the spread of African swine fever across Asia, but none of them so far has specifically mentioned that the disease has reached the North.

"To prevent African swine fever from spreading, it's crucial to detect and slaughter the pigs infected with the virus at the right time," North Korean scientist Jon Sung Chil said in an interview with Pyongyang's official Rodong Sinmun newspaper, which called for an all-out effort by the North's farming industry and homes to prevent the spread of the disease.

South Korean government believes the North raises about 2.6 million pigs in 14 government-run or co-operative farms. Oh Beom-seok, an official from South Korea's agriculture ministry, said the South is prepared to provide diagnosis kits, disinfectants and other equipment should the North ask for help.

"We are trying to gain as much information possible from the OIE or North Korean officials there ... but so far, there has been no additional report of an outbreak (in North Korea)," Oh said.

The ministry said government workers have caught more than 1,000 wild boars in South Korea for blood tests, which have so far came back negative. While workers plan to test 2,000 more wild boars, the ministry said none of the animals so far was caught from border areas, where a ban on hunting rifles make the animals harder to control.

South Korea's Defence Ministry, which is monitoring the movement of wild boars through heat sensors installed along the border, said it would be difficult for wild boars to cross over the barbed wire fences in the mine-scattered border zone. But government officials say there's still a possibility that the animals could swim across rivers.