Published on 25 November 2024

African swine fever: Complex virus leaves many questions unanswered

African swine fever (ASF) is a major viral disease that affects both domestic and wild pigs. The ASF virus was first detected in Africa, from where it has spread worldwide, causing significant economic losses in the pig sector. In Africa the virus is transmitted by soft-bodied ticks, primarily between African wild pig species such as warthogs, bushpigs and brush-eared pigs. However, these species do not usually become infected. In contrast, ASF infection of domestic pigs or Eurasian wild pigs leads to serious disease, often accompanied by high mortality. Transmission between domestic pigs and Eurasian wild pigs mainly occurs through direct animal-to-animal contact or through contaminated products. There are currently no registered vaccines or treatment options. ASF poses a threat not only to the pig sector, but also to wild pig populations.

African swine fever infects wild and domestic pigs — © IVI

No cases of ASF have occurred in Switzerland to date. However, the risk of introduction is high, not least because the disease has been present for several years in large parts of Europe and in some of Switzerland’s direct neighbours. The ASF virus is harmless to humans. As a highly complex DNA virus, it poses major challenges for research in virology and immunology.

• Risk of ASP and role of the IVI

  African swine fever poses a real risk to animal health in Switzerland. The virus has been spreading in Europe for several years and has caused outbreaks in Switzerland’s immediate neighbours, Germany and Italy. Because the virus mainly affects wild pigs, it is difficult to control. There is currently no safe vaccine against ASF, which is classed as a highly contagious disease under the Animal Diseases Ordinance. The IVI plays a key role in the fight against ASF on various levels:

  • As the national reference laboratory, the IVI provides diagnostics for the virus.
  • Research into the virus is crucial in order to prevent and control the disease.

• What does the IVI do?

  • We provide ASF diagnostics LINK for ongoing surveillance and in the event of an outbreak. Exclusion testing enables us to test domestic pigs for ASF virus where the disease is unlikely to be present but veterinarians, veterinary pathologists and livestock farmers want to rule it out with certainty. These exclusion tests are vital in order to detect a possible ASF entry into a pig farm as early as possible.
  • We support the FSVO in the ASF wild boar national early detection programme and early detection in domestic pigs. For this purpose, blood or spleen swabs from dead or infected wild boar are sent to the IVI, mainly by hunters, gamekeepers and veterinarians. Around 200 investigations are carried out under the ASF wild boar early detection programme every year.
  • We advise the Swiss Veterinary Service by providing technical expertise in various committees.
  • We conduct basic research to investigate the function of viral genes and their interaction with pig cells.
  • We identify the viral antigens relevant for the immune response.
  • We are researching the protective immune response against ASF in order to create a basis for vaccine development.
  • We participate in vaccine development and assess the efficacy of various vaccine candidates in international collaboration.
  • We have a strong network of connections in the field of ASF and work with many international partner organisations.

  When working on complex topics such as African swine fever, it is essential to maintain strong diagnostic and research networks. Key partner institutions of the IVI include the Universität Bern, Friedrich-Loeffler-Institut FLI (DE), Wageningen University (NL), Ghent University (BE), Centro de investigación en sanidad animal (Madrid, ES) and the Pirbright Institute (GB).
  
  The IVI has been part of the European ASFaVIP consortium since 2024. The aim of the consortium is to bring a safe and efficient vaccine to market in Europe as quickly as possible. The IVI also carries out basic and applied research in order to understand the immune system’s protective mechanisms against ASF and is taking innovative steps to develop an effective and safe ASF vaccine.

  Further information about the ASFaVIP project and the activities of the IVI – Text by Nicole Jegerlehner (SAT, ASVM):

  • The IVI is researching a vaccine for African swine fever

    PDF553.14 kB5 February 2025

  

  IVI activities (green) in relation to the main problems (dark red) posed by African swine fever

• Main findings

  • We were able to show that the pigs’ hygiene status and associated immune status influence the course of the disease in attenuated variants of African swine fever virus (ASFV). We are using this fact to find out what type of immune response is necessary in order for vaccination to protect against the disease.
  • With the aid of systematic laboratory tests, we were able to define the protective immune response in more detail and use these findings to develop vaccines.
  • We were able to reconstruct the entire ASFV genome in yeast, allowing us to establish a molecular platform for manipulating the ASFV genome.
  • We have produced different attenuated ASFV variants by removing individual non-essential genes from the ASFV genome. These viruses are used for the targeted study of viral gene functions and for evaluating live-attenuated vaccine candidates.
  • We have identified the viral antigens that trigger an immune response during infection with attenuated ASFV variants or vaccine candidates.

Einblicke in unsere Arbeit

African swine fever : Clinical symptoms in pigs - how and when to react?

Although Switzerland is not presently afflicted by the African swine fever (ASF), the Institute for Virology and Immunology (IVI) is nevertheless working to determine the properties of the ASF strains that are circulating in Europe. Were there an outbreak in Switzerland, it would be important to ensure efficient and reliable laboratory diagnostics and to be continually abreast of the newest research findings in order to be able to deliver critical virological, immunological, clinical and pathological information to the Swiss veterinary service (in German).

• Interview with Dr. med. vet Nicolas Ruggli and with Prof. Dr. med. vet Charaf Benarafa - IVI

  PDF212.37 kB26 November 2024

A highly sensitive system for detection of ASFV infection in cell culture

The method of choice for the detection of ASFV is PCR. However, PCR provides no information on whether the sample contains live virus or on virus infectivity. The latter is determined by a complex process of virus isolation and titration. To simplify and automate this process, we have established a novel method for the detection of infectious ASFV.

This research has been published in the journal Viruses.

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Different factors affect progression of the disease

The hygienic status of pigs plays an important role in disease severity during infection with an attenuated strain of the African swine fever (ASF) virus). Studying surviving animals will contribute to the eventual development of a vaccine. Recent research conducted at the IVI in collaboration with the University of Bern have just been published in the journal PLOS Pathogens.

African swine fever : the hygienic status of pigs plays an important role in the development of the disease

What are the most important results of your study? How will these results eventually contribute to development of a vaccine? Listen to the answers of Kemal Mehinagic.

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A molecular platform for ASFV genome manipulation in yeast

A molecular platform for ASFV genome manipulation in yeast

Aiming to establish a molecular platform for ASFV genome manipulation, we have reconstructed the entire genome of a highly pathogenic ASFV isolate in yeast. This method has been published in the journal STAR Protocols.

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More information

Federal Food safety and Veterinary FSVO

• Afrikanische Schweinepest (German)
• Nationales Früherkennungsprogramm ASP Wildschwein (German)

Friedrich-Löffler-Institut FLI:

• Karten zur ASP | Friedrich-Loeffler-Institut (German)