Swine vesicular disease
Aetiology Epidemiology Diagnosis Prevention and Control References
AETIOLOGY
Classification of the causative agent
Virus family Picornaviridae, genus Enterovirus
Resistance to physical and chemical action
Temperature: Preserved by refrigeration and freezing, inactivated by 56°C/1 hour pH: Stable over a wide range of pH Disinfectants: In the presence of organic matter, inactivated by sodium hydroxide (1% combined with detergent). For personal disinfection in the absence of gross organic matter, disinfectants, such as oxidising agents, iodophores, acids etc., are suitable if combined with detergent Survival: Resistant to fermentation and smoking processes. May remain in hams for 180 days, dried sausages for >1 year, and in processed intestinal casings for >2 years EPIDEMIOLOGY
- Morbidity rate in herds may be low but high in groups of pigs (in pens)
- Does not cause death
Hosts
- Pigs
- Humans: laboratory personnel may seroconvert
Transmission
- Virus readily infects via lesions in skin and mucosa. Direct contact or contact with excretions from in-fected pigs. Faecal contamination is a major source of virus spread, often within contaminated vehicles
- Meat scraps and swill derived from infected pigs
Virulent material
- Intestinal tract is the primary site of infection
- All tissues contain virus during the viraemic period
- Epithelium from vesicles, vesicular fluid, faeces, and blood of sick animals
Occurrence
The disease has been recorded in Hong Kong, Japan and several European countries
For detailed information on occurrence, see recent issues of World Animal HealthDIAGNOSIS
Incubation period is 2-7 days
Clinical diagnosis
The clinical signs of SVD may easily be confused with those of Foot and mouth disease (FMD)
- Sudden appearance of lameness in several animals in a group in close contact
- Elevation of body temperature by 2-4°C
- On hard surfaces, animals may be observed to limp, stand with arched back, or refuse to move even in the presence of food. Young animals are more severely affected
- Vesicles occur on the snout and along the coronary band and interdigital spaces of the feet, and rarely on the epithelium of the buccal cavity, the tongue and the teats
- Vesicle rupture results in erosions on the skin of the limbs and the coronary bands of the feet. Foot pads may be loosened. Pigs, particularly young stock, may lose the horny hoof
- Recovery occurs usually within 1 week, with a maximum of 3 weeks
- Some strains produce only mild clinical signs or are asymptomatic
Lesions
Vesicle formation is the only known lesion directly attributable to the infection
Differential diagnosis
- Vesicular stomatitis
- Vesicular exanthema of swine
- Foot and mouth disease
NB!! Laboratory confirmation is necessary Laboratory diagnosis
Procedures
Identification of the agent
- ELISA
- Direct complement fixation test
- Cell-culture isolation (pig-derived cell cultures)
Serological tests
- Virus neutralisation
(prescribed test in the Manual)
- ELISA
Samples
Although the virus is very stable, samples must be submitted under the same conditions as those suspected to contain FMD virus, i.e. at pH 7.2-7.4.
Virus isolation
- Vesicular fluid
- Epithelium from vesicles: at least 1 g in PBS containing glycerin 50% (pH 7.2-7.4)
- Unclotted whole blood samples, collected during the febrile period
- Faecal samples from animals with and without lesions
Serological tests
- Serum samples (1-2 ml)
- Also collect serum from other pigs on the premises to test for evidence of subclinical disease
NB!! As for FMD, special precautions are required when sending perishable suspect SVD material within and between countries. See Manual, Chapter 1.4. PREVENTION AND CONTROL
- No treatment
- No vaccination
Sanitary prophylaxis
- Strict quarantine
- Elimination of infected and contact pigs
- Prohibition of feeding with ship or aircraft garbage
- Thorough cooking of garbage
- Control of movement of pigs and vehicles used for transporting pigs
- Thorough disinfection of premises, transport vehicles, and equipment
Medical prophylaxis
Laboratory workers should observe the same caution that applies to any microbiologically contaminated material that may have the potential to cause human infection
REFERENCES AND OTHER INFORMATION
- Reference experts and laboratories
- Classified as an OIE List A disease (A030)
- Chapter 2.1.3. in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.
- Terrestrial Animal Health Code
- Numerous other references - see the Index
- World Animal Health .
- Current Animal Health Status (Disease Information)
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Contact : scientific.dept@oie.int