Detection of Porcine Circovirus Type 2 in Feces of Pigs with or without Enteric Disease by Polymerase Chain Reaction

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Abstract
To establish the sensitive polymerase chain reaction(PCR) method and detect porcine circovirus type 2 (PCV2) from intestines and feces of commercial swine herds with or without enteric disease, intestinal samples from 68 pigs and 29 fecal samples from commercial swine farms were collected. A primer set, forward primer 5′-GAAGAATGGAAGAAGCGG-3′ and reverse primer 5′-CTCACAGCAGTAGACAGGT-3′, could detect the virus at a concentration as low as 2 infectious virions per milliliter under controlled conditions using PK-15 cell-adapted PCV2. The genomic nucleotide sequences of open reading frame 1 (ORF1) PCR products from fecal samples were found to have complete homology with other PCV2s deposited in the GenBank database. Transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhea virus (PEDV) as the other enteric pathogens were also investigated by performing duplex reverse transcription-PCR (RT-PCR). Among 63 pigs with clinical enteric disease, 18 PCV2s (14 from intestines and 4 from feces), 7 TGEVs from intestines, and 18 PEDVs (14 from intestines and 4 from feces) were detected by PCR and the duplex RT-PCR. In 34 pigs (14 from intestines and 20 from feces) without clinical enteric disease, only PCV2 was detected in 19 pigs (3 from intestines and 16 from feces). Both PEDV and PCV2 were found in 6 pigs with clinical enteric disease. Among 15 PCV2 samples that were PCR-positive, 4 were culture-positive at passage level 3 in PK-15 cells. These results reveal that PCV2 is shed through the feces of pigs without clinical enteric disease, which suggests the potentiality of the fecal–oral transmission of PCV2 in feces.