African swine fever

African swine fever is one of the most important viral diseases in pigs. It is a systemic disease and is notifiable on most countries.

Alternative names: ASF

Information

African swine fever is caused by an iridovirus. There are different strains with different virulence. Its clinical condition  is quite similar to that of classical swine fever and many common diseases, such as salmonella, therefore a laboratory diagnosis is required. Its control involves the stamping-out. As of classical swine fever, these viruses survive for a long time in frozen carcasses.

 

Symptoms

Lactating piglets

  • Vomiting.
  • Diarrhea.
  • Lack of coordination.
  • Conjunctivitis.
  • High fever.
  • Sudden death.
  • Malformations.
  • Very weak piglets at birth (congenital tremor).

 

Sows

  • Loss of appetite.
  • High fever.
  • Abortions.
  • Increment of stillbirths.
  • Increment of mummified piglets.
  • Seizures.
  • Lack of coordination.
  • Diarrhea.
  • General reproductive failure.
  • Blue discoloration of the skin.


Nursery and fattening

  • Depressed pigs - with their head down.
  • They stop eating.
  • Diarrhea.
  • Eye discharge.
  • Persistent high fever.
  • Nervous signs.
  • Seizures.
  • Lack of coordination.
  • Blue discoloration of the skin.
  • High mortality.

 

Causes / Contributing Factors

  • The virus is transmitted from infected or carrier pigs through nasal and mouth discharges, urine and feces. It is very contagious.
  • The virus can be transmitted by ticks (especially of the genus Ornithodorus)
  • There is airborne transmission.
  • It can enter a farm through contaminated meat (can be transmitted through uncooked pork meat or cured meat).
  • Mechanical transmission is common through boots, clothing, trucks, etc.
  • Co-infection with PRRS virus.

 

Diagnosis

  • It presents post-mortem changes with hemorrhagic lymph nodes, necrotic areas in the spleen, multiple small hemorrhages in kidneys and button ulcers in the intestine.
  • In all suspected cases the diagnosis should be confirmed by laboratory analysis.
  • Laboratory analysis include the identification of viral antigen, isolation of the virus and the presence of antibodies in serum. In most countries, the ASF is a notifiable disease.

 

Control/Prevention

  • Currently, no effective vaccines available.
  • Stamping-out.
  • Countries free of ASF prevent infection from abroad controlling the importation of pigs and pig meat products, if not properly processed,  if them come from countries with ASF. In addition, the organic fraction of waste that may contain meat products must be sterilized by heat.
  • In Africa and affected areas: they must keep wild boars and materials contaminated away from producing farms.