African swine fever

Test code: S0127 - Ultrasensitive detection of African swine fever virus by real time PCR

African swine fever (ASF) is a highly contagious, generalized disease of pigs caused by a DNA virus formerly classified as an iridovirus (Iridoviridae) but recently re-classified into a newly created family of viruses called Asfarviridae - a name derived from "African Swine Fever And Related Viruses.” Within that family it has been allocated to the Genus Asfivirus of which it is the only member. Different strains of ASF virus exhibit varying virulence. The virus is very resistant to inactivation, and can persist up to one month in contaminated pens, in meat up to 15 weeks and in processed hams up to 6 months.

High concentrations of ASF virus are shed in secretions and excretions from acutely infected pigs. Because the virus survives well in the environment and in meat, its spread can occur via contaminated livestock pens or by feeding contaminated garbage. The virus also spreads through pig to pig contact, ticks and other biting insect vectors, contaminated injection needles or mechanically by humans and equipment.

Infected pigs usually have an incubation period of 5-15 days before the disease may manifest itself in a number of forms:

• Peracute - pigs are found moribund with death following rapidly.
• Acute - high fever (up to 42C.) after 1-2 days anorexia and recumbency, skin blotching, diarrhea and abortion. Mortality close to 100% within 7 days.
• Subacute - fluctuating or continuous fever for up to 20 days, with milder clinical signs.
• Chronic - transient recurring fever with stunting and emaciation. Possible pneumonia, lameness, skin lesions, and secondary infections.

Recovered pigs may remain chronically infected and excrete the virus for 6 weeks after infection. Contaminated pens and garbage feeding, particularly with material from international airports or seaports, are documented methods of spread due to the resistance of the virus to inactivation.

African Swine Fever is clinically, and upon necropsy, very similar to Hog Cholera (also known as "Classical Swine Fever"). Laboratory tests are required to differentiate the two diseases.

Serological diagnosis and culture identification have been used to detect ASF but they are generally slow and not very specific. Molecular detection by PCR can provide rapid, specific and sensitive results (McKillen et al., 2007).

Utilities:

• Confirm the disease causing agent
• Identify ASF virus carriers
• Ensure that animal colonies and populations are free of ASF
• Early prevention of spread of the virus among animals
• Minimize human exposure to the virus
• Safety monitoring of biological products that derive from animals

References:
McKillen, J., Hjertner, B., Millar, A., McNeilly, F., Belák, S., Adair, B. and Allan, G. (2007) Molecular beacon real-time PCR detection of swine viruses. J Virol Methods. 140:155-65.

Specimen requirements: 0.5 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or 0.5 ml feces, or rectal swab, or 0.5 ml fresh, frozen or fixed tissue.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected