Age-specific Prevalence of Porcine Reproductive and Respiratory Syndrome Virus, Porcine Circovirus Type 2, and Mycoplasma hyopneumoniae in Korea Pig Farms

Porcine respiratory disease complex (PRDC) continues to be a significant economic problem to the swine industry. Porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), and Mycoplasma hyopneumoniae (MH) are considered to be the most important pathogens that cause PRDC. In this study, we investigated the prevalence of antibodies against PRRSV and MH in the serum of sows and piglets from 89 domestic commercial pig farms by ELISA, and the presence of viral nucleic acids of PRRSV, including North American and European PRRS, and PCV2 was also investigated in the serum of sows and piglets from 89 domestic commercial pig farms by real-time PCR. In case of PRRSV, 78.7% (70/89) of sows were positive for PRRSV antibody, and 96.6% (86/89) of piglets were positive for PRRSV antibody. For MH, 76.4% (68/89) of sows showed positive for MH antibody. In the PRRSV viral nucleic acid detection experiment, 36.0% (32/89) of sows were positive for PRRSV nucleic acids, and virus nucleic acid was detected in 83.1% (74/89) of piglets. In case of virus type, both North American and European types were detected. In case of PCV2, 15.7% (14/89) of sows were positive for PCV2 nucleic acids. Conclusively, PCV2, PRRSV, and MH were widely distributed in pig farms in Korea. These prevalence data related with PRDC provides clinical information for vaccination strategy and development for the control of PRDC.

Survey of porcine respiratory disease complex-associated pathogens among commercial pig farms in Korea via oral fluid method

Oral fluid analysis for herd monitoring is of interest to the commercial pig production in Korea. The aim of this study was to investigate pathogen-positive rates and correlations among eight pathogens associated with porcine respiratory disease complex by analyzing oral fluid samples from 214 pig groups from 56 commercial farms. Samples collected by a rope-chewing method underwent reverse-transcriptase polymerase chain reaction (RT-PCR) or standard polymerase chain reaction (PCR) analysis, depending on the microorganism. Pathogens were divided into virus and bacteria groups. The former consisted of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 (PCV2), and the latter Pasteurella multocida, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae (MHP), Mycoplasma hyorhinis, and Streptococcus suis (SS). All pathogens were detected more than once by PCR. Age-based analysis showed the PCR-positive rate increased with increasing age for PCV2 and MHP, whereas SS showed the opposite. Correlations between pathogens were assessed among 36 different pair combinations; only seven pairs showed statistically significant correlations. In conclusion, the oral fluid method could be a feasible way to detect various swine respiratory disease pathogens and, therefore, could complement current monitoring systems for respiratory diseases in the swine industry.