Christine Pelland from South West Ontario Veterinary Services,Atypical Porcine Pestivirus (APPV): Quantifying The Severity!

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For the longest time we did not know that most of the cases of Congenital Tremor or “Shaky  Pig”  were  caused  by  Atypical Porcine Pestivirus (APPV). This discovery was due to analysis of affected pig tissue looking for  a  virus  in  affected  pigs  more  frequently  that unaffected pigs. Recently, piglets from a high-health status  farm  began  exhibiting  congenital  tremors, high pre-weaning mortality and increased incidence of   splayed   legs.   Postmortem   microscopic examination of affected tissues identified scattered white  matter  vacuoles  in  the  cerebellum  and underlying   brainstem   of   affected   piglets.   A metagenomic  sequencing  effort looked  for  potential  viral infections that could explain the disease and APPV was  identified  as  the  main  microbial  species  in piglets affected by congenital tremor. This allowed the researchers to quantify the severity of  the  disease  in  this  case  that  was  attributed  to APPV.

  • APPV  affected  pigs  had  higher  pre-weaning mortality rates (46.4% vs 15.3%).
  • APPV  affected  pigs  had  a  higher  incidence  of splayed  legs  (33.0%  vs  0.8%)  compared  to unaffected piglets.
  • APPV  affected  pigs  (Congenital  Tremor)  had higher  viral  titer  (P  <  0.15)  and  larger  birth weights  (P  <  0.05)  compared  to  normal  litter-mates.
  • APPV Strains appear to cluster based on region but there were still significant differences within regions

Take Home Messages

  • Preweaning  mortality  in  pigs  affected  with APPV was 46.4% vs 15.3% in unaffected pigs. This  demonstrates  just  how  severe  the  case fatality  rate  of  Congenital  Tremor  associated with APPV can be.
  • Increased  incidence  of  splayleg  has  been described  when  Congenital  Tremor  is  active and this case demonstrates that 1/3 of affected pigs can show evidence of splaylegs. Splaylegs are certainly not helpful when you are already shaking  as  you  attempt  to  suckle  or  move about the pen.

Submitted by Christine Pelland, DVM

Ref: Sutton KM, Lahmers KK, Harris SP, Wijesena HR, Mote BE, Kachman SD, Borza T, Ciobanu DC. Detection of Atypical Porcine Pestivirus  Genome  in  Newborn  Piglets  Affected  by  Congenital Tremor and High Pre-weaning Mortality.J Anim Sci. 2019 Aug 9. pii: skz267. doi: 10.1093/jas/skz267. [Epub ahead of print]

 

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