Prevalence of the Novel Torque Teno Sus Virus Species k2b from Pigs in the United States and Lack of Association with Post-Weaning Multisystemic Wasting Syndrome or Mulberry Heart Disease.

The family Anelloviridae includes a number of viruses infecting humans (Torque teno viruses, TTV) and other animals including swine (Torque teno sus viruses, TTSuV). Two genetically distinct TTSuV species have been identified from swine thus far (TTSuV1 and TTSuVk2), although their definitive association with disease remains debatable. In 2012, a novel TTSuV species was identified from commercial swine serum and classified in the genus Kappatorquevirus as TTSuVk2b. The other Kappatorquevirus species, TTSuVk2a, has been associated with post-weaning multisystemic wasting syndrome (PMWS) when coinfected with porcine circovirus type 2 (PCV2). Therefore, in this study, we initially amplified a portion of TTSuVk2b ORF1 and, subsequently, assessed the molecular prevalence of the virus in pigs in the United States. A total of 127 serum and 115 tissue samples were obtained from pigs with PMWS or mulberry heart disease (MHD) in six states and tested by PCR for the presence of TTSuVk2b DNA. Approximately 27.6% of the serum and 21.7% of tissue samples tested positive for TTSuVk2b DNA, and the positive products were confirmed by sequencing. However, we did not detect a correlation between TTSuVk2b infection and PMWS or MHD. The near full-length genomic sequence of US TTSuVk2b was determined, and sequence analysis revealed that the US TTSuVk2b isolates were 95% identical to the TTSuVk2b isolate from Spain, with most of the variations clustering in ORF1. We conclude that the novel TTSuVk2b species is present in pigs in the United States and its potential association with a disease warrants further investigation.