Detection of porcine circovirus type 2 (PCV2) in the Philippines and the complexity of PCV2-associated disease diagnosis.

Porcine circovirus type 2 (PCV2), an important pig viral pathogen, can cause porcine circovirus-associated disease (PCVAD), resulting in economic losses associated with decreased growth and mortalities. The diagnosis of PCVAD is complex requiring clinical, pathological and virological approaches. This study assessed PCV2 infection using histopathology and immunohistochemistry (IHC) on tissue samples and quantitative polymerase chain reaction (qPCR) on serum samples from 47 grower-finisher pigs allocated in three clinical groups in the Philippines. Typical PCV2 histopathological lesions were observed in mediastinal lymph nodes (MLN) of eight of 47 pigs. Lymphoid depletion was seen in all eight pigs and granulomatous inflammation in one of these pigs. Four of these eight pigs were PCV2 positive by both IHC and qPCR. IHC revealed PCV2 antigen in 8 pigs in at least one of the following tissues: MLN (5/8), spleen (3/8), tonsils (4/8) and lungs (5/8). PCV2 antigen was observed in 3/8 MLN with lymphoid depletion and in one MLN with depletion and granulomatous inflammation. The qPCR test showed that 33 sera had a non-detectable level, twelve had < 106 and two had > 106 PCV2 DNA copies/ml serum. One pig with lymphoid depletion had > 106 PCV2 DNA copies/ml serum, and another pig without MLN lesions also had > 106 PCV2 DNA copies/ml serum. These findings suggest that PCVAD is present in the Philippines and confirm the challenges of PCVAD diagnosis as different patterns of results were obtained from the different tests.

Prevalence and Risk Factors Associated with Gross Pulmonary Lesions in Slaughtered Pigs in Smallholder and Commercial Farms in Two Provinces in the Philippines.

A cross-sectional study of lungs from 1,887 randomly selected pigs from 471 farms from two provinces in the Philippines was carried out to estimate the prevalence of gross pathological lesions, identify potential risk factors and spatial clustering associated with high lung or pleurisy score farms. Lungs from pigs were scored at slaughter. Interviews with the farm managers were conducted to collect information about farm management and biosecurity practices. Of lungs examined, 48% had a lung score above 6 (maximum was 55) and 22% showed pleurisy. When data were aggregated at the farm level, commercial farms were at higher risk of being high lung score farms and high pleurisy farms compared to smallholder farms (P < 0.01). Variables that were associated with an increased risk of a farm being a high lung score farm included the presence of a market pen on the farm, not vaccinating against hog cholera and the presence of another piggery within 500 m. Practicing "feedback" (feeding pig manure, viscera or aborted material to pigs), presence of another piggery within 500 m, and allowing commercial livestock vehicles on farm were all associated with an increased risk of being a high pleurisy farm. Spatial analyses revealed a primary 9.6 km-radius cluster of 39 farms with high lung and pleurisy scores in the southeast of Bulacan province. High lung and pleurisy score farms could be targeted to improve on-farm disease control programs to reduce the risk of respiratory diseases. Clusters of high scoring farms could be prioritized for further investigations or for coordinating intervention efforts.