Occurrence and Associated Risk Factors of Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus Type 2 Infections in Greece.

The objective of the present study was to identify factors associated with the probability of being polymerase chain reaction (PCR) positive and the level of porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2) occurrence in Greek farms. The study included 56 pig farms, with a total population of 22.500 sows, which represent about 40% of the entire capacity of the Greek swine production. A total of 896 blood samples (224 pools*4 samples/pool = 896 samples) from breeding stock, weaners, growers, and finishers were collected from each farm and organized in pools of 4 samples size. Further, data regarding herd health management protocols were collected. The sera were tested for PRRSV and PCV2, using real-time PCR (RT-PCR). The results indicated that both viruses remain a major challenge for the Greek swine industry. Main risk factors involved in the infection process by these viruses were identified. In particular, vaccination programs such as the mass PRRSV vaccination with modified-live virus (MLV) in breeding stock during the last stages of gestation or with killed-virus (KV) during the middle of gestation are more likely to be associated with PRRSV PCR-positivity. Farms with low biosecurity level are associated with higher PRRSV circulation. It has also been revealed that breeding stock is more likely to be associated with PCV2 circulation compared to weaners and growers. In conclusion, our results could be the basis of the development of surveillance protocols for a national monitoring system for PRRSV and PCV2, which could prevent future infection of Greek farms.