First detected in East Africa in the early 1900s, African swine fever (ASF) has a high mortality rate in domestic pigs. The World Organisation for Animal Health (WOAH) describes it as a “highly contagious viral disease” that is “not a danger to human health”. Despite this, it has “devastating effects on pig populations and the farming economy”. The WOAH also indicates that the virus is “highly resistant in the environment” and survives in “various pork products”. Thus, human behaviours, when not managed, enable the spread of the disease across borders.
A publication in the Veterinary Journal in 2018 described the “challenge” of controlling the disease. The authors identified the lack of a vaccine as central to this. The only available control measures are “strict quarantine and biosecurity, animal movement restrictions, and slaughtering affected/exposed animals”.
The current crisis
The Guardian reports that the current outbreak is “believed to threaten around three-quarters of the world’s herds”. It is linked to an appearance of the virus in 2007, in Georgia, which spread “beyond the Caucasus” thanks to its ability to survive “up to 1,000 days in frozen meat”.
In 2018 the virus was detected in China, which is “home to around half of the world’s pigs”. In 2020, it was confirmed in Germany, which is “home to one of the EU’s largest swine herds”. This sustained wave of infection is “the biggest animal disease outbreak we’ve ever had on the plant”, according to Professor Dirk Pfeiffer of City University of Hong Kong.
Vaccine hopes
WOAH suggests that pork meat is a primary source of animal protein, “accounting for more than 35% of the global meat intake”. Furthermore, it affects wild boars as well as domestic pigs, so presents a “concern for biodiversity and the balance of ecosystems”. Therefore, the pressure is on to develop a vaccine. Current attempts include an EU-funded project: VACDIVA. This was launched in 2019 with the goal of providing 3 safe and effective pilot vaccines. With their sights set on a roll out in late 2024, the researchers must answer questions about the international efficacy of a vaccine developed in Spain, and the frequency of administration.
They are not the only scientists with ASF ambitions. Harbin Veterinary Research Institute in China claims to have made progress towards a live attenuated vaccine. The Pirbright Institute in the UK has a team dedicated to “refining” a vaccine. Dr Linda Dixon leads ASF research and is often asked why it is taking so long to produce a successful candidate.
“People are quite nervous about it because the thing with a live attenuated vaccine – which all of these are – is basically you’re releasing a live virus into the field. And there’s not enough of a history to know exactly what’s going to happen.”
A messy past
The Guardian reports that “the risks” of vaccination were “laid bare” earlier in 2022 when Vietnam announced it would administer a vaccine to 600,000 animals across 20 provinces. Unfortunately, within three months the programme was stopped after around 750 pigs were reported to have died. The company that produced the vaccine has suggested that the deaths occurred in provinces where farms had ignored specific instructions. However, the complexity of the virus and the importance of a successful vaccine has been brought home to researchers across the world.
As with other diseases, ASF provides a reminder of global inequalities. The paper in Veterinary Journal recalls the effect of culling campaigns and pig movement on “global trade and people’s livelihoods”.
“The impact is often greatest for resource poor livestock farmers in developing countries, who rely on pigs as an additional source of income and a relatively cheap source of protein.”
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