Blood-based feed, not wild boars, drove ASF's spread across South Korea

Feed made from infected pig blood distributed nationwide; National Assembly Research Service calls for review of same-species feeding rules

A new analysis has found that blood-derived feed, not wild boars, was the primary driver behind the nationwide spread of African swine fever (ASF) earlier this year — the first time feed ingredients have been confirmed as a transmission route in South Korea.

The National Assembly Research Service said in a report published Monday that porcine plasma protein feed was the main cause of this year's large-scale ASF outbreak.

ASF is a Class 1 livestock infectious disease with a fatality rate of up to 100 percent. Since January, 24 cases have been confirmed simultaneously across the country, leading to the culling of approximately 170,000 pigs — the worst toll since the disease was first detected in South Korea in 2019.

Wild boars and contaminated food-waste feed had long been considered the primary vectors of ASF transmission. After the disease first appeared in 2019, prevention efforts focused on border areas and centered on controlling wild boar populations and erecting fences.

Timing of porcine plasma protein feed administration by pig rearing stage [National Assembly Research Service]

This year, however, the pattern was different.

An epidemiological investigation by the Ministry of Agriculture, Food and Rural Affairs found that 21 of the 24 ASF cases confirmed this year involved a genotype (IGR-I) distinct from those seen in previous domestic outbreaks. Investigators determined that blood from infected pigs at a farm in Dangjin in 2025 had been supplied to a feed ingredient manufacturer. The porcine plasma protein feed produced from that blood was then distributed to farms nationwide, rapidly spreading the virus.

Porcine plasma protein is a protein ingredient made by separating plasma from pig blood and drying it. It is commonly used as a feed additive to promote growth and boost immunity in piglets. The investigation confirmed a link between farms that used plasma protein feed and ASF outbreaks. Piglets inoculated with test samples containing domestically produced plasma protein died within seven to nine days.

Production and supply chain of porcine plasma protein [National Assembly Research Service]

The report said the outbreak should prompt a broader public debate on so-called "same-species feeding" — the practice of feeding pigs protein derived from other pigs. The EU has banned the feeding of same-species protein to animals since 2001, but South Korea has no separate regulation covering pigs.

The National Assembly Research Service outlined three priorities going forward: strengthening the inspection and management of blood-derived feed, expanding the biosecurity manager regime to pig farms, and accelerating ASF vaccine development while tightening quarantine measures. It particularly advised reviewing whether the biosecurity manager system currently applied to large-scale poultry farms should be extended to hog operations.

"This ASF outbreak is the first confirmed case of a new infection route that cannot be addressed by the existing wild-boar-centered biosecurity system alone," the research service said, calling for stronger management of blood-derived feed, an increase in qualified veterinarians, and the establishment of a broader biosecurity framework.

adastra@heraldcorp.com