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]