Classical Swine Fever

Test code: S0126 - Ultrasensitive detection of classical swine fever virus by reverse transcription coupled real time PCR

Classical swine fever (CSF), also called hog cholera or swine fever, is caused by a pestivirus within the flaviviridae family. Bovine viral diarrhea virus and border disease virus are other members of the pestivirus genus. Domestic pigs and wild boar are the only natural reservoirs of CSF. Humans are not susceptible to the CSF virus.

Infected pigs can transmit the virus to susceptible pigs by direct or indirect contact. Ingestion and inhalation are the most common routes of infection, but transmission has also occurred via conjunctival or mucous membrane contact, contamination of skin abrasions, insemination, and transfer of blood.

Infected animals can shed the virus in saliva, feces, blood, urine, and nasal discharge. Contaminated equipment, vehicles, clothing, and footwear can mechanically transmit the virus to susceptible animals. Consumption of uncooked, infected pork scraps has resulted in outbreaks of CSF. The CSF virus can survive in these products for many months.

Transplacental infection with strains of low virulence can produce chronically infected piglets. In addition, recovered pigs can still shed the virus for a long period of time, making them another potential source of infection and outbreaks.

CSF can occur in acute or chronic forms. In the acute form of CSF, affected animals exhibit a high fever, severe depression, and anorexia. Blotchy, purple discoloration of the skin is frequently observed. Affected pigs may stand with arched backs. Abortions, still births, and weak litters are observed when pregnant sows are infected with the CSF virus. Newborn piglets frequently develop neurologic signs including tremors and convulsions. Death usually occurs in 10 to 15 days.

The chronic form of CSF results in similar clinical signs, but they are intermittent and less severe. Anorexia, fever, hair loss, and constipation alternating with diarrhea are usually observed. This form can also result in “carrier-sow” syndrome, in which chronically infected sows produce persistently infected piglets. These animals become chronic carriers of the virus and transmit infection when introduced into naïve herds. In some herds, the only clinical sign observed when CSF viral infection is of low virulence is poor reproductive performance. Congenital infection with CSF virus of low virulence may result in tremors, runting, poor growth, and death.

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

Utilities:

• Confirm the disease causing agent
• Identify CSF virus carriers
• Ensure that animal colonies and populations are free of CSF
• 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:
Depner, K., Hoffmann, B. and Beer, M. (2007) Evaluation of real-time RT-PCR assay for the routine intra vitam diagnosis of classical swine fever. Vet Microbiol. 121:338-43.

Specimen requirements: 0.5 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or 0.5 ml feces, or 0.5 ml urine, or 0.5 ml tissue, or rectal swab, or nasal swab, shipped overnight at room temperature.

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 reverse transcription coupled real time PCR

Normal range: Nondetected