PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME (PRRS).

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Causative Agent(s)

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). The virus belongs to the order Nidovirales and family Arteriviridae.

The PRRSV species forms two major genetic lineages represented by type 1 and type 2 genotypes.

Clinical Presentation and Epidemiology

The disease occurs worldwide as outbreaks characterized by severe reproductive losses, respiratory disease, reduction in growth rate, and increased mortality.

The clinical signs observed in infected pigs are fever, anorexia, lethargy, dyspnoea, hyperpnea, hyperaemia or cyanosis on extremities.

PRRS reproductive failure is present in herds when litters are small, weak, dead, and autolyzed or mummified.

Oedematous and haemorrhagic enlargement of umbilical cords of aborted or stillborn pigs is commonly noticed.

 

Diagnostic Considerations

The samples required for laboratory diagnosis are serum, tonsils, lungs, lung lavage and oropharyngeal scrapings.

The following laboratory tests are used to diagnose this disease: Virus isolation, fluorescent antibody test on frozen, samples, immunohistochemistry using formalin-fixed tissues, Reverse transcriptase-polymerase chain reaction, ELISA, indirect fluorescent antibody and virus neutralization.

Management and Treatment

There is no single successful approach for the managing of PRRS. Available vaccines have limited success. It is very helpful to improve biosecurity at all stages of production including using all-in-all-out management at all stages of production. If possible, depopulate, clean, and disinfect the facilities and, after a few weeks, repopulate with stock free of PRRS. Boars introduced into negative herds should be quarantined for 60-90 days after purchase and confirmed negative serologically. Stocks entering PRRS- positive herds require acclimatization to resident PRRS virus. Semen for artificial insemination should be certified negative for PRRS virus using PCR.

Where it is not possible to depopulated like in breeding herds, herd stabilization can sometimes be accomplished by vaccination, intentional whole-herd infection, aggressive acclimatization of replacement breeding stock, or combinations of these strategies.

There is no specific treatment for PRRS. Antibiotics may be useful only in controlling secondary infections. Non-steroidal anti-inflammatory are useful in ameliorating symptoms during acute disease.