African Swine Fever (ASF) remains the most destructive threat to the global pig industry, featuring high contagiousness, nearly 100% mortality, and no fully commercialized universal vaccine for large-scale global application. Entering the post-pandemic era, the global ASF epidemic has undergone obvious changes. Large-scale, explosive outbreaks have gradually disappeared, while asymptomatic hidden infections, low-level virus transmission, and sporadic atypical cases have become the dominant epidemic risks for pig farms. Traditional passive prevention methods relying on emergency culling and blind disinfection can no longer support long-term, stable farm biosafety.

Nowadays, refined daily management, active risk monitoring and precise virus screening have become the core of modern ASF prevention and control. Among all practical prevention technologies, ASF dual-negative detection stands out as the most reliable and operable solution to eliminate hidden virus carriers and achieve whole-herd purification. Supported by the continuous upgrading of gene-deleted ASF vaccines and the innovative field application of the DIVA strategy, a new integrated ASF prevention system has taken shape. Through years of large-scale promotion and iterative optimization in real farming scenarios, China has built a mature, replicable and field-proven prevention system centered on dual-negative detection, providing actionable and practical guidance for pig farms worldwide.

1. Why Dual-Negative Detection Is Indispensable for Post-Pandemic ASF Control

In the early stage of the ASF epidemic, most farms and regional prevention departments only took emergency disposal measures after confirmed outbreaks. However, post-pandemic ASF is characterized by invisible transmission. A large number of infected pigs show no obvious clinical symptoms but continuously shed viruses into the environment, leading to repeated recurring outbreaks that are difficult to eradicate in pig herds.
Conventional single detection methods have prominent limitations in actual farm operation. Single nucleic acid testing easily misses latent infected pigs with low viral load. Single serological antibody testing cannot distinguish true virus infection from immune interference, resulting in inaccurate risk judgment. To solve these universal industry pain points, ASF dual-negative detection has become the unified core standard for precise ASF prevention. It organically combines nucleic acid detection for active live virus screening and serological antibody detection for infection traceability.
The biggest practical advantage of dual-negative detection is achieving zero omission in pig herd risk screening. Nucleic acid testing accurately identifies pigs carrying live ASF viruses to cut off ongoing virus transmission. Antibody testing screens out individuals with a history of ASF infection to prevent virus reactivation and secondary spread. This double-check mechanism completely makes up for the loopholes of single detection, greatly improves farm biosafety levels, and supports long-term stable breeding and sustainable herd purification.
At present, ASF dual-negative detection is no longer a temporary emergency testing tool. It has evolved into a standardized daily management tool covering pig breeding, slaughter processing and live pig circulation, which is essential for normalized ASF prevention globally.

2. Standard On-Farm SOP for ASF Dual-Negative Detection

The core definition of ASF dual-negative detection is that all tested pigs must meet two key qualification standards: ASF viral nucleic acid negative and ASF specific antibody negative. This dual-index comprehensive judgment covers the entire ASF infection cycle, adapting to daily farm monitoring, pre-delivery pig inspection, and long-term herd purification work. The complete operating SOP is summarized based on China’s official veterinary inspection specifications and massive real-world farm verification.

2.1 Standard Sample Collection and Preservation Management

Field detection samples mainly include pig serum samples, pig tissue samples and farm environmental samples. For live pig testing, venous blood is collected and centrifuged to obtain serum for antibody detection. Tonsil and lymph node tissues, the most sensitive detection materials for ASF, are collected for viral nucleic acid testing. All samples need strict low-temperature storage and sealed transportation to avoid contamination, nucleic acid degradation and invalid test results. Synchronous environmental sampling of pig pens, feeding equipment and disinfection areas is also required to realize full-dimensional virus monitoring.

2.2 Two Core Detection Technologies for Dual-Negative Screening

Nucleic acid detection (active virus screening): Fluorescent quantitative PCR (real-time qPCR) is the mainstream and most reliable technology adopted by farms and professional testing institutions. With ultra-high sensitivity and specificity, it can detect trace ASF viral nucleic acid in latent infected pigs, which cannot be identified by manual clinical observation. Take the Ringbio ASFV Ag Real-time qPCR kit as an example, which can be used to detect ASFV sequences in multiple biological and environmental samples,

Serological antibody detection (infection traceability screening): Standardized ELISA detection kits are used to test ASF-specific antibodies in pig serum. A positive antibody result indicates historical ASF infection or atypical immune response, reminding farms to isolate suspicious herds and arrange re-inspection in a timely manner. The Ringbio ASFV P30 Antibody Indirect ELISA Kit is known for high sensitivity, specificity and good reproducibility, which was already approved by the Chinese Ministry of Agriculture and Rural Affairs.

2.3 Field Result Judgment and Abnormal Disposal Rules

Dual-negative qualified standard: Pigs with both negative nucleic acid and negative antibody results are confirmed clean, free from ASF infection and infection history, and safe for daily breeding, market trading and slaughter processing.
Any single positive result is defined as abnormal. Nucleic acid positivity means active live virus infection with ongoing transmission risks. Antibody positivity means potential historical infection and hidden recurrence risks. All abnormal individuals must be isolated immediately, re-tested repeatedly, and disposed of in strict accordance with standardized epidemic prevention procedures to completely block virus transmission chains.
In industrial practical application, China has unified dual-negative detection mandatory standards for cross-regional live pig transportation and slaughterhouse entry inspection, effectively blocking the cross-regional spread of hidden ASF viruses in the entire pig industry chain.

3. Real-World Practices and Field Effects of China’s Dual-Negative Prevention System

China has fully promoted the coverage of dual-negative detection technology in pig breeding, slaughter processing and live pig circulation links. After years of field practice and technical iteration, a complete, operable and efficient whole-industry-chain ASF prevention system has been formed. This set of prevention modes is highly practical and replicable, suitable for popularization in various pig farming scenarios worldwide.
First, normalized full-coverage dual-negative monitoring has built a nationwide ASF risk early warning system. Continuous double-index screening effectively reduces the hidden infection rate of pig herds and greatly cuts down sporadic ASF cases. A large number of domestic pig farms have achieved long-term zero-ASF breeding through dual-negative purification management, and multiple regional ASF-free breeding zones have been successfully built.
Second, dual-negative detection standardizes the supervision of the entire pig industry chain. It fills the technical loopholes of traditional single detection supervision, comprehensively guarantees the biosafety of live pigs and pork products, and effectively stabilizes domestic pig production capacity and market supply balance.
Third, China’s dual-negative prevention model solves common pain points in global ASF prevention, such as invisible herd infection, difficult circulation supervision and low purification efficiency. The standardized on-site operation norms and whole-chain management experience provide reliable real-world references for global pig farms to carry out refined ASF prevention.

4. Current Progress and Practical Application of ASF Vaccines

Vaccine immunization is the most economical and effective long-term solution for ASF prevention and herd purification. Restricted by the complex genetic structure and easy variation of ASF virus, there is no universal commercial ASF vaccine for large-scale global promotion at this stage. However, global and Chinese scientific research institutions have made remarkable phased progress in vaccine research and development.
Gene-deleted live attenuated vaccines: This is the most promising ASF vaccine type for practical application. By deleting virulence-related genes of wild ASF virus, the optimized vaccine strain has high safety and strong immune protection. Multiple candidate gene-deleted vaccines have entered clinical trials and have verified stable protective effects in real farm scenarios.
Inactivated vaccines: This traditional vaccine type has high biosafety, but its immunogenicity is weak, unable to produce sufficient and stable protective antibodies in pig herds. Its practical prevention effect is limited, and the technology is still in continuous optimization.
Subunit vaccines and vector vaccines: These new-type vaccines have the advantages of high safety and convenient production, but their core protective antigen screening is not yet mature, resulting in limited field protection effects, which needs further technical improvement.
In summary, gene-deleted live attenuated vaccines will be the mainstream immune product for future ASF precise prevention and purification. Meanwhile, the DIVA strategy is the core indispensable supporting technology for the large-scale popularization of such vaccines.

5. DIVA Strategy and Its Practical Value in On-Site ASF Prevention

DIVA (Differentiating Infected from Vaccinated Animals) is a key practical detection technology for modern ASF prevention, with the core function of accurately distinguishing vaccinated healthy pigs from wild ASF virus-infected pigs.
Traditional epidemic prevention faces a key dilemma: common vaccines cannot distinguish immune antibodies induced by vaccination from antibodies produced by wild virus infection. After large-scale vaccination, universal antibody positivity in pig herds makes it impossible to screen hidden infected individuals through serological detection, forming serious epidemic monitoring blind spots.
Gene-deleted ASF vaccines adopted in modern prevention remove specific marker antigen genes of wild ASF virus. After vaccination, healthy pigs only produce protective antibodies corresponding to vaccine antigens without marker antibodies. In contrast, pigs infected with wild ASF virus will produce complete antibodies including marker antibodies. Supporting DIVA detection kits can accurately identify the difference between the two, realizing precise screening of infected pigs from immunized herds.
In real-world ASF prevention, the organic combination of dual-negative detection + DIVA dynamic monitoring builds a scientific dual-protection system. Farms adopt dual-negative detection to screen and confirm clean virus-free herds before vaccination to ensure the safety of immunization; after vaccination, DIVA detection is used for long-term dynamic monitoring to timely discover wild virus invasion and secondary infection risks. This integrated model perfectly coordinates immune protection and epidemic risk screening, greatly improving the success rate of farm ASF purification. What's notable is that, Ringbio has also developed the ASFV P72/CDv2/MFG Triplex Real-time qPCR kit, which can be used to identify CDV2 or MFG removed vaccine sequences and wild viral infections.

6. Conclusion

In the post-pandemic era, refined, standardized and normalized daily management is the key to successful long-term ASF prevention. As a field-verified core technology, ASF dual-negative detection fundamentally solves the global problem of hidden virus transmission and becomes the cornerstone of safe pig breeding. Through large-scale real-world practice and continuous optimization, China has formed a complete, replicable whole-industry-chain ASF prevention system, providing mature practical experience for global pig industry epidemic prevention.
With the continuous maturity of gene-deleted ASF vaccine technology and supporting DIVA detection systems, the integrated prevention model of regular dual-negative screening + scientific vaccination + DIVA dynamic monitoring will become the mainstream solution for global ASF prevention. This optimized strategy will help global pig farms effectively resist ASF risks and realize long-term stable and sustainable development of the pig industry.

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