PCV3-associated reproductive failure in pig herds in Brazil

Porcine circovirus type 3 (PCV3) has been widely detected worldwide in healthy and sick pigs. Recently its association with clinical disease and reproductive failure has been proven through the detection of intralesional viral mRNA in affected pigs. This study aims to describe the occurrence of PCV3-associated reproductive failure (abortions) in sow herds in southern Brazil. Eleven fetuses from five different litters from two herds were analyzed. These herds reported an increase in the rate of late-gestation abortions, stillbirths, and the percentage of mummified piglets. At gross examination, six of the fetuses had large caudally rotated ears and one fetus was mummified. Microscopically, multisystemic vasculitis, lymphocytic interstitial pneumonia, myocarditis, and encephalitis were observed. These six fetuses with gross and histological lesions were positive in qPCR analysis for PCV3, and PCV3 transcription was shown through in situ hybridization (ISH-RNA) within the histologic lesions. Samples from all 11 fetuses tested negative in PCR exam for Porcine Circovirus type 1 and 2, Porcine Reproductive and Respiratory Syndrome, Porcine Parvovirus, and Atypical Porcine Pestivirus. Furthermore, based on the ORF2 analysis, the PCV3a clade was identified. This is the first report of PCV3a-associated reproductive failure in pig herds in South America.