Since its arrival in Georgia in 2007, African swine fever has spread rapidly, both to the west, through Russia and Europe, and more recently to the east. Although the virus is harmless to humans, the current outbreak of African swine fever could have serious global repercussions for food security and economic stability. Already, China – home to half the world’s pig population – has lost a third of its pigs to the disease (about 100 million), possibly more.
Vietnam, where the pork industry is worth approximately $4 billion, has confirmed several hundred outbreaks. Other countries affected are North and South Korea, Myanmar, Philippines, East Timor, and Laos.
The disease is carried by pigs, wild boar and soft-bodied ticks, and there is currently no vaccine or cure. However, according to leaders in the field, containment is possible through a combination of biosecurity, government and farmer action along with information and awareness from everyone.
Read how swine fever is spread on the European Food Safety Authority website and watch their video.
It’s a double stranded DNA virus, and it can survive in cold temperatures for months, and can survive in frozen meat for months, if not years. Because it can be carried by wild boar as well as domestic pigs, it’s tough to contain. It can survive in soil, so patches in forests where other sick wild boar have died can remain contaminated, and when other wild boar nose around, they can become infected months later. It becomes very difficult to control.
With classical swine fever (caused by an unrelated virus), the solution was to leave vaccine bait for wild boars to consume. But an effective DIVA vaccine for African swine fever could be about 10 years away, Dr. Roberts estimates. Complicating the situation is the use of illegal or unsafe non-DIVA vaccines in some areas. DIVA vaccines (DIVA stands for Differentiating Infected from Vaccinated Animals) induce an immune response which is different from that induced by natural infection, and are important for animals where the owner intends to trade them later on. They allow owners to show which have been vaccinated and which were infected. Non-DIVA vaccines don’t allow for that.
You may also find that large-scale vaccination drives the evolution of the virus – which is why you get successive waves of different strains of avian flu in Asia, and the viruses can become more pathogenic. Nevertheless, this is a tricky virus to vaccinate against as inducing a protective immune response is difficult. With this genotype in Europe, we don’t see any naturally immune animals, so it’s not thought they become immune and can be re-infected.
The challenges of containment
That leaves containment as the best option for addressing the disease, bringing with it challenges of education, information and compensation. Prof. Trevor Drew, Director of the Australian Animal Health Laboratory, explained:
It’s a difficult disease to control, but it’s not impossible. The normal disinfectants are very effective – so as Helen says, it’s a hardy virus and can survive in the environment for some time. But boiling pig swill for half an hour will kill it. So for those countries that swill feed, boiling feed will render the virus inactive.
The problem is that people don’t.
Lack of compliance with biosecurity and swill feeding rules is at the heart of the issue, Prof. Drew explained. The normal mechanisms in industrial production are effective at controlling swine fevers (African and classical), but problems arise when they aren’t followed. People don’t dip their boots in disinfectant, some veterinarians travel from farm to farm without following best practice, in decontamination, and transporters and feed distributors drive from one place to the next with contaminated vehicles. And at the international level, meat and products illegally carried by passengers present a significant risk of further spread, with several countries reporting significant proportions of such meat containing the virus.
“The virus can move quite slowly through a farm at the beginning, so in a large farm, the disease may be present for two or three weeks before mortalities become a concern,” he added. “But if you introduce the disease via feed, then you get a kind of synchronized infection, with very large numbers of pigs becoming infected at the same time. That can be absolutely devastating, and you’ll see huge numbers of pigs dead in five to 10 days.”
The disease has so far been reported in China, most of Southeast Asia and parts of Eastern Europe, as well as a small pocket in wild boar in East Belgium. The implications, however, reach beyond those areas, as Prof. Drew outlined:
“Food security and regional stability go hand in hand, so obviously a lot of people in Asia are very concerned about this,” he said. “(At) the Australian Animal Health Laboratory, we have a strong outreach program. We’re working with the likes of the World Organization for Animal Health and the Food and Agriculture Organization of the UN to help these countries receive advice on diagnosis, detection and control, along with urging them to prevent further spread to uninfected countries.
“But it’s a huge challenge,” he added, “especially where most of the pig production is small scale and even backyard. Those people can be hard to reach, and the impacts can be profound because they depend on pig production to supplement their income.”
Education is key, then, and its necessity is not limited to Asia. With this genotype now being reported in several countries in East Europe as well as Eastern EU, taking steps to contain it is essential. As Dr. Roberts said:
We worry about people bringing back pork products from from affected countries. It’s illegal if you bring any meat or dairy product in from a third country, so the border force can take the product off you, but if someone has just come from Europe, we don’t have that recourse. So a lot of our work is about communication, and explaining why people shouldn’t bring things back. Fortunately the commercial pigs sector is very aware of this risk, but smallholders are a different matter – they really need to register with us so we can keep them in touch with any new developments and remind them about good practice.
Read the latest research on African swine fever
The implications of the disease on economic prosperity and global food security are severe, as Dr. Roberts and Prof. Drew articulate. Below you will find a selection of current research from Elsevier’s journals, which can be of use in addressing the development of a vaccine and for researchers working with the agricultural community on containment and good practice for biosecurity.
Some are freely available through our open access program, others we have made freely available for the next three years, until October 15, 2022.
- Dominic Smith, Tarni Cooper, Abrao Pereira, Joanita Bendita da Costa Jong, Counting the cost: The potential impact of African Swine Fever on smallholders in Timor-Leste, One Health, Volume 8, December 2019,
- Daniel Pérez-Núñez, Sun-Young Sunwoo, Elena G. Sánchez, Nicholas Haley, Raquel García-Belmonte, Marisa Nogal, Igor Morozov, Daniel Madden, Natasha N. Gaudreault, Lina Mur, Vinay Shivanna, Juergen A. Richt, Yolanda Revilla: Evaluation of a viral DNA-protein immunization strategy against African swine fever in domestic pig, Veterinary Immunology and Immunopathology (2019)
- Kayode Olayinka Afolabi, Benson Chuks Iweriebor, Anthony Ifeanyi Okoh, Larry Chikwelu Obi: Increasing diversity of swine parvoviruses and their epidemiology in African pigs, Infection, Genetics and Evolution (2019)
- Vlad Petrovan, Fangfeng Yuan, Yanhua Li, Pengcheng Shang, Maria V. Murgia, Saurav Misra, Raymond R.R. Rowland, Ying Fang: Development and characterization of monoclonal antibodies against p30 protein of African swine fever virus, Virus Research (2019)
- Shehnaz Lokhandwala, Vlad Petrovan, Luca Popescu, Neha Sangewar, Catherine Elijah, Ana Stoian, Matthew Olcha, Lindsey Ennen, Jocelyn Bray, Richard P. Bishop, Suryakant D. Waghela, Maureen Sheahan, Raymond R.R. Rowland, Waithaka Mwang: Adenovirus-vectored African Swine Fever Virus antigen cocktails are immunogenic but not protective against intranasal challenge with Georgia 2007/1 isolate, Veterinary Microbiology (2019)
- C. Gallardo, J. Fernández-Pinero, M. Arias: African swine fever (ASF) diagnosis, an essential tool in the epidemiological investigation, Virus Research (2019)
- Erik Arabyan, Armen Kotsynyan, Astghik Hakobyan, Hovakim Zakaryan: Antiviral agents against African swine fever virus, Virus Research (2019)
- L.K. Dixon, M. Islam, R. Nash, A.L. Reis: African swine fever virus evasion of host defences, Virus Research (2019)
- P.L. Eblé, T.J. Hagenaars, E. Weesendorp, S. Quak, H.W. Moonen-Leusen, W.L.A. Loeffen: Transmission of African Swine Fever Virus via carrier (survivor) pigs does occur, Veterinary Microbiology (2019)
- Karl Ståhl, Susanna Sternberg-Lewerin, Sandra Blome, Arvo Viltrop, Mary-Louise Penrith, Erika Chenais: Lack of evidence for long term carriers of African swine fever virus - a systematic review, Virus Research (2019)
- Tinka Jelsma, Joris J. Wijnker, Bregtje Smid, Eline Verheij, Wim H.M. van der Poel, Henk J. Wisselink: Salt inactivation of classical swine fever virus and African swine fever virus in porcine intestines confirms the existing in vitro casings model, Veterinary Microbiology (2019)
- Alexander Malogolovkin, Denis Kolbasov: Genetic and antigenic diversity of African swine fever virus, Virus Research (2019)
- Margarida Simões, Ferdinando B. Freitas, Alexandre Leitão, Carlos Martins, Fernando Ferreira: African swine fever virus replication events and cell nucleus: New insights and perspectives, Virus Research (2019)