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AFRICAN SWINE FEVER 

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WHAT IS AFRICAN SWINE FEVER?

African swine fever (ASF) is a highly contagious and deadly viral disease that can impact domestic and wild pigs.  It is not a human pathogen, but ASF can be devastating to the health of swine and cause significant economic and production losses to farmers and pork processors1.   In 2019, an increase in ASF outbreaks was reported in several African, Asian and European countries.   The ASF virus is a large, enveloped, DNA virus.  The genus is Asfivirus, a member of the Asfarviridae family.       

WHAT ARE THE SYMPTOMS?

Disease severity can vary and is dependent on the virulence, or severity, of the ASF virus strain.  The range of virulence spans low, moderately and highly virulent strains.  These different strains and their virulence can affect the health of pigs in several ways2:

  • The milder but longer term form of ASF is caused by low or moderately virulent strains of ASF.  Mortality rate is low and the illness is characterized by weight loss, occasional fever and irreversible damage to areas of the skin.
  • A more serious form of ASF is caused by moderately virulent strains.  Illness lasts from 5 to 30 days and the mortality rate can be as high as 70%, with death occurring within 15 to 45 days.
  • The most serious form of ASF  of ASF is caused by highly virulent ASF strains.  Symptoms include high fever, reddening of the skin, vomiting and diarrhea (sometimes bloody).  The onset of symptoms is rapid. The mortality rate often approaches 100%, with death occurring 6 to 13 days after infection.  Death can be sudden with few illness symptoms.  

 

HOW IS IT TRANSMITTED?

There are multiple modes of infection transmission:

  • Direct transmission of the virus between sick and healthy pigs.
  • Indirect transmission of the virus through feeding on garbage containing ASF-infected meat.  ASF virus can remain infectious for three to six months in uncooked pork products.
  • Transmission of ASF virus through clothes, tools, vehicles and other objects. 
  • Transmission through the bite of an infected tick of the genus Ornithodoros.

 

HOW IS IT CONTROLLED?

There is no approved vaccine against ASF, unlike classical swine fever (hog cholera) which is caused by a different virus1.   The main preventive approaches are awareness, education and implementation of biosecurity principles, including segregation, control, cleaning and disinfection, and pest management. 

During outbreaks, control of ASF can be difficult and must be adapted to the specific epidemiological situation.  Key steps in controlling and limiting outbreaks of ASF are1,3:

  • Early detection of ASF through active surveillance and veterinary diagnosis.
  • Humane killing of animals with proper disposal of carcasses and waste.
  • Thorough cleaning and disinfection.
  • Personnel hygiene, including hand washing, boot-wash and dedicated PPE.
  • Enhanced pest management to control ticks.
  • Zoning, compartmentalization and movement controls.
  • Strict biosecurity measures on farms.
  • Knowledge and management of the wild boar population and coordination across veterinary services, wildlife and forestry authorities.

Prevention is the primary focus in countries or regions that are free of disease.  Key measures include1,3:

  • Implementation of appropriate import policies and biosecurity measures.
  • Proper disposal of waste food from aircraft, ships or vehicles coming from affected countries.
  • Policing illegal imports of live pigs and pork products from affected countries.
  • Knowledge and management of the wild boar population and coordination across veterinary services, wildlife and forestry authorities.

ASF can be inactivated through heat - 56°C (133°F)/70 minutes or 60°C (140°F)/20 minutes or higher temperatures1. Many different chemistries at critical concentrations and exposure times are known to kill ASF, including quaternary ammonium compounds, peracetic acid, bleach, citric acid and some iodine compounds3,4,5. Only products with country or region regulatory approval against ASF or a surrogate can be used.  For example, for a virucidal claim in Europe, EN 14675 is the relevant European standard. The EN standard recognizes Bovine enterovirus Type 1 as the surrogate virus and can be applied to ASF virus inactivation. 

 

REFERENCES AND FURTHER INFORMATION

1. https://www.oie.int/en/animal-health-in-the-world/animal-diseases/african-swine-fever/#A
2. https://www.oie.int/fileadmin/Home/eng/Our_scientific_expertise/docs/pdf/ASFV
3. https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/african-swine-fever
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458555/ 
5. https://www.aphis.usda.gov/animal_health/downloads/animal_diseases/swine/asf-entry.pdf