Swine Vesicular Disease

Test code: S0125

Test name: Ultrasensitive detection of swine vesicular disease virus by reverse transcription coupled real time PCR

Swine vesicular disease virus (SVDV) is a porcine enterovirus in the family Picornaviridae. It is antigenically related to the human enterovirus Coxsackie B-5 but is unrelated to other known porcine enteroviruses.

Pigs are the only species naturally infected, but laboratory personnel have been infected due to occupational exposure.

Pigs infected with this virus show almost identical clinical signs to foot-and-
mouth disease (FMD) in pigs. The clinical signs include fever, salivation and lameness. Vesicles and erosions can be seen on the snout, mammary glands, coronary band, and interdigital areas. Vesicles in the oral cavity are relatively rare. The infection may be subclinical, mild, or severe depending on the virulence of the strain. Severe signs are generally seen only in pigs housed on damp concrete. Younger animals can be more severely affected. Neurologic signs due to encephalitis, such as shivering, unsteady gait, and chorea (rhythmic jerking) of the legs, are rare. Abortion is not typically seen. Recovery occurs within 2 to 3 weeks, usually with little permanent damage.

Transmission of the virus can occur by ingestion of contaminated meat scraps or contact with infected animals or their feces. Pigs can excrete the virus from the nose, mouth, and in feces up to 48 hours before clinical signs are seen. Virus can be shed in the feces for up to three months following infection. Furthermore, SVDV can survive for long periods of time in the environment; it is resistant to heat up to 69°C (157°F) and pH ranging from 2.5 to 12. It can also survive up to two years in lymphoid tissue contained in dried, salted, or smoked meat.

Swine vesicular disease is considered to be moderately contagious. Compared to FMD, morbidity is lower and the lesions are less severe. Mortality is not generally a concern with swine vesicular disease.

Although neither disease is currently present in North America, differentiation of these two vesicular diseases is still important because the introduction of FMD could cause severe economic losses.

Swine vesicular disease or other vesicular diseases should be suspected when vesicles or erosions are found on the snout and/or feet of pigs. Differentials for swine vesicular disease include FMD, vesicular stomatitis, vesicular exanthema of swine, and chemical or thermal burns. In swine vesicular disease outbreaks, pigs will be the only species affected, the lesions will be mild, and there will be no mortality. Other vesicular diseases must be ruled out with laboratory tests.

SVDV can be identified using enzyme-linked immunosorbent assay (ELISA), the direct complement fixation test, and virus isolation in pig-derived cell cultures. Virus neutralization and ELISA can be used for serological diagnosis. However, all these methods are relatively nonspecific and are labor intensive to perform. Molecular detection by PCR can enable rapid, specific and sensitive characterization of the virus (Ferris et al., 2006; Reid et al. 2004).

Utilities:

• Confirm the disease causing agent
• Identify SVDV virus carriers
• Ensure that animal colonies and populations are free of SVDV
• 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:
Ferris, N.P., King, D.P., Reid, S.M., Hutchings, G.H., Shaw, A.E., Paton, D.J., Goris, N., Haas, B., Hoffmann, B., Brocchi, E., Bugnetti, M., Dekker, A. and De Clercq, K. (2006) Foot-and-mouth disease virus: a first inter-laboratory comparison trial to evaluate virus isolation and RT-PCR detection methods. Vet Microbiol. 117:130-40.

Reid, S.M., Paton, D.J., Wilsden, G., Hutchings, G.H., King, D.P., Ferris, N.P. and Alexandersen, S. (2004) Use of automated real-time reverse transcription-polymerase chain reaction (RT-PCR) to monitor experimental swine vesicular disease virus infection in pigs. J. Comp. Pathol. 131:308-17.

Specimen requirements: Vesicular fluid or lesion swab, or 0.5 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or 0.5 ml feces, or 0.5 ml tissue, 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