Studies of porcine circovirus type 2, porcine boca-like virus and torque teno virus indicate the presence of multiple viral infections in postweaning multisystemic wasting syndrome pigs

In a previous study, using random amplification and large-scale sequencing technology, we identified a novel porcine parvovirus belonging to the genus Bocavirus in the background of porcine circovirus type 2 (PCV-2) in Swedish pigs with postweaning multisystemic wasting syndrome (PMWS). In addition to bocavirus we demonstrated the presence of torque teno virus (TTV) genogroups 1 and 2 in these cases of PMWS, indicating the simultaneous presence of several viruses in this disease complex. In the present study, 34 PMWS-affected animals and 24 pigs without PMWS were screened by PCR for the presence of PCV-2, TTV-1, TTV-2 and porcine boca-like virus (Pbo-likeV). The studies revealed the following infection rates in the PMWS-affected pigs: PCV-2 100%, TTV-1 77%, TTV-2 94% and Pbo-likeV 88%. In comparison. the pigs without PMWS had the following rates: PCV-2 80%, TTV-1 79%, TTV-2 83% and Pbo-likeV 46%. The sequence identity between the different Swedish Pbo-likeV sequences ranged between 98% and 100%. By checking co-infection, it was found that 71% of the PMWS-affected pigs harbor simultaneously all these viruses. As a contrast, in the group without PMWS only 33% of the animals were positive simultaneously for these viruses. These observations indicate a multiple viral infection in PMWS-affected pigs. It has to be studied further if the clinical manifestation of PMWS might be due to synergistic effects of different viruses acting together. (C) 2010 Elsevier B.V. All rights reserved.