Development of Polioencephalomyelitis in Cesarean-Derived Colostrum-Deprived Pigs Following Experimental Inoculation with Either Teschovirus A Serotype 2 or Serotype 11

Abstract

Teschovirus encephalomyelitis is a sporadic disease associated with Teschovirus A (PTV) serotype 1 and, less frequently, other serotypes. In recent years, the number of cases submitted to the Iowa State University Veterinary Diagnostic Laboratory with a history of posterior paresis has increased. Submission histories from various regions of the United States suggest a trend for clinical disease to persist in herds and affect a wider age-range of pigs than historically reported. Polioencephalitis and/or myelitis was consistently present and PTV was detected in affected neural tissue by PCR in a portion of cases. Sequencing from two clinical cases identified PTV-2 and PTV-11. To assess neuropathogenicity of these isolates, 5-week-old cesarean derived and colostrum-deprived pigs were assigned to three groups: negative control (n = 4), PTV-2-inoculated (n = 7), and PTV-11-inoculated (n = 7). Three PTV-2-inoculated pigs developed mild incoordination of the hind limbs, one of which progressed to posterior ataxia. While all PTV-11-inoculated pigs showed severe neurological signs consistent with Teschovirus encephalomyelitis, no evidences of neurological signs were observed in sham-inoculated animals. All PTV-2- and PTV-11-inoculated pigs had microscopic lesions consistent with Teschovirus encephalomyelitis. To our knowledge, this is the first description of PTV-11 and experimental study demonstrating the neuropathogenicity of PTV-11 in the United States.

Keywords: Porcine teschovirus; Porcine teschovirus 11; Porcine teschovirus 2; Talfan disease; Teschen disease; Teschovirus A; Teschovirus encephalomyelitis; poliomyelitis.

Figure 1

Phylogenetic trees illustrating the genetic relation of 79 unique polyprotein sequences with isolates PTV-2 USA/IA65463/2014 and PTV-11 USA/IA09592/2013. Polyprotein phylogenetic tree (A); Major capsid protein (VP1) gene phylogenetic tree (B); 3D^pol phylogenetic tree illustrating the genetic relation of 43 unique 3D gene sequences with isolates PTV-2 USA/IA65463/2014 and PTV-11 USA/IA09592/2013 (C). Branch distances expressed as percent of homology. Scale bar represents substitutions per site.

Figure 2

Pig No. 74, inoculated with PTV-2, day post-inoculation 11 (DPI 11). Lymphoplasmacytic myelitis with expansion of the Virchow–Robin spaces (*) and multifocal areas of gliosis (▲) in cervical spinal cord (A), lumbar spinal cord (B), and midbrain (C); Pig No. 77 inoculated with PTV-11, day post-inoculation 11 (DPI 11) Lymphoplasmacytic myelitis with expansion of the Virchow–Robin spaces (*) and multifocal areas of gliosis (▲) in cervical spinal cord (D), lumbar spinal cord (E), and midbrain (F).