African swine fever is becoming a long-term management problem in endemic regions

African swine fever control strategies may need to evolve as the virus shifts from explosive outbreaks towards persistent circulation in some regions. A new perspective in Frontiers in Veterinary Science argues that endemicity, viral diversification, changing control practices and the growing use of vaccines are creating a more complex epidemiological landscape.

Classical ASF control has relied heavily on stamping out, movement restrictions and rapid response to highly fatal outbreaks. But the authors note that in areas with prolonged circulation, including parts of Africa and Asia, infection can increasingly present with milder, chronic or atypical clinical signs. Animals may survive longer, remain infectious and contribute to continued transmission.

That change matters for surveillance. Systems that depend mainly on obvious mortality or severe clinical disease may become less sensitive if attenuated or atypical variants circulate. The authors warn that passive surveillance alone may therefore miss ongoing transmission, particularly when whole-genome sequencing is limited.

Control measures can influence viral evolution

The paper also raises a less intuitive issue: control programmes themselves can create selective pressures. Where removal decisions are triggered mainly by severe clinical signs, highly virulent infections may be detected and eliminated quickly, while pigs with milder or prolonged infections remain in the population for longer. In theory, this can favour variants that are less clinically obvious and harder to detect.

This is one reason the authors argue that ASF control should increasingly be based on laboratory-confirmed infection and sensitive surveillance, rather than clinical severity alone.

Vaccination brings opportunities and new risks

Vaccination is becoming an increasingly important component of ASF control, particularly in regions where eradication through culling alone has proved difficult. However, ASF remains a challenging vaccine target. The virus has a genome of around 170–190 kbp encoding more than 150 proteins, many involved in immune modulation. Conventional inactivated, subunit and vector-based approaches have not yet provided consistently reliable protection, leaving live attenuated vaccines as the most promising current platform.

Live vaccines nevertheless introduce specific concerns because they replicate in vaccinated pigs. Potential risks include prolonged viraemia, shedding, reversion to virulence, transmission outside the target population and recombination with circulating field strains. Reports of recombinant and vaccine-related viruses in Asia have strengthened these concerns.

The issue could become particularly important where vaccine strains and wild-type ASFV circulate simultaneously in wild boar populations.

DIVA tests remain an important gap

Another major limitation is the lack of widely validated DIVA systems capable of reliably distinguishing infected from vaccinated animals under field conditions. Without robust DIVA diagnostics, vaccination can complicate disease reporting, outbreak investigation and international trade. The authors therefore consider DIVA-compatible testing an essential component of any large-scale vaccination strategy rather than an optional technical refinement.

Surveillance needs to become more comparable

ASF surveillance also varies considerably between countries in carcass-search intensity, diagnostic protocols and thresholds for genome sequencing. This matters because differences in surveillance effort can create very different apparent epidemiological pictures even when underlying transmission is similar. In wild boar in particular, rapid detection depends heavily on systematic carcass searches and laboratory confirmation.

The authors consequently call for stronger coordination of vaccination, surveillance and genomic monitoring, while recognising that implementation cannot be identical everywhere. Measures designed for large industrial pig systems may be unrealistic for smallholder production where veterinary access, resources and biosecurity capacity are limited.

From eradication campaigns to adaptive control

The central argument is that ASF may increasingly need to be treated as a long-term adaptive management challenge in regions where the virus has become entrenched. Vaccines may reduce mortality and production losses, but they do not necessarily eliminate circulation. At the same time, viral evolution, wildlife reservoirs and heterogeneous production systems make a return to a simple pre-outbreak situation increasingly difficult.

The study therefore argues for a shift in some settings from short-term eradication logic towards sustained risk management combining sensitive surveillance, genomics, vaccination oversight and internationally coordinated disease control.