After decades of speculation, congenital tremors in neonatal piglets have been confirmed to be caused by a virus: researchers recently identified a new type of porcine pestivirus.
This was communicated by two research teams, independently but simultaneously working on comparable studies, carried out in the United States and the Netherlands. Both presentations were given at the International Pig Veterinary Society (IPVS) Congress, in Dublin, Ireland.
Often, congenital tremors are complicated by splayleg. Photo: Henk Riswick
Clinical signs of congenital tremor in piglets
The phenomenon congenital tremors is best described as piglets showing muscular tremor, ataxia and inability to stand and suck. Typically, pigs affected with congenital tremors don't tremble when they are sleeping; often they also suffer from splayleg. Most clinical signs disappear over time and little mortality occurs.
For decades, the true origin of 'dancing pigs' was unknown, a viral cause was considered very likely but remained unidentified until recently.
Iowa State University research
In late 2015, the team from Iowa State University, in Ames, IA, United States, already communicated briefly about the pestivirus they had discovered and associated with congenital tremors.
Paulo Arruda, Iowa State University. Photo: Vincent ter Beek
As Paulo Arruda explained on behalf of the US research team, they discovered the pestivirus from field cases with congenital tremors and identified it as being closely related to a Chinese bat pestivirus. In an attempt to reproduce disease, they inoculated piglets in utero at both 45 and 62 days of gestation. These piglets indeed were affected with congenital tremors, at prevalence ranging from 57 to 100%.
Research in the Netherlands
Initial research in the Netherlands into the virus was already started up as early as 2012 – the team including researchers from the University of Amsterdam, Utrecht University and MSD Animal Health needed time to collect all relevant data and prove their findings.
Ad de Groof, MSD Animal Health. Photo: Vincent ter Beek
Not only did this research team manage to replicate the disease, Dr Ad de Groof from MSD Animal Health explained at IPVS, the Dutch also demonstrated that the virus can transmit transplacentally, as in their research, several sows were inoculated with the virus at day 32 of gestation. "In 2 of 3 litters born from these gilts, several piglets presented with mild to moderate clinical signs of congenital tremor type A-II," they wrote.
The Dutch team suggested a name for the new virus: congenital tremor associated porcine pestivirus (CT-APPv).