Pre-registration efficacy studies of a novel marker vaccine against classical swine fever on target animals

Background: Classical swine fever (CSF) or hog cholera is a highly contagious and devastating disease of Suidae caused by an enveloped single-stranded RNA virus (CSFV) of the family Flaviviridae, genus Pestivirus. CSF has vast economic and trade significance all over the world, and it has the massive potential to spread rapidly from country to country. This is the reason why the World Organisation for Animal Health has listed CSF as a Notifiable Disease and it is also considered a transboundary animal disease. Objective: The objective of the present studies was to determine the efficacy of a single dose of a newly developed marker vaccine candidate against CSF, administered intramuscularly or orally in 6-week-old domestic piglets with and without maternally derived antibodies (MDAs) against Pestiviruses, to provide protection against a challenge with the highly virulent CSFV strain Koslov 14 days post vaccination. Materials and Methods: In both experiments two test groups were formed with 15 animals each, one group for intramuscular (im.), while another one for oral (p.o.) immunisation. The control groups contained 10 animals as unvaccinated controls, respectively. All piglets were oronasally challenged with the highly virulent CSF virus (CSFV) strain Koslov 14 days post-vaccination. Results and Discussion: The vaccine candidate when administered im. provided complete protection in MDA- animals, while p.o. administration triggered only partial protection. Furthermore, we found that the presence of the MDAs had negative effect on the efficacy of the vaccine candidate. However, this was greatly influenced by the route of administration. Based on our observations, im. administration is recommended to achieve better immune response during the CSF control programs. The vaccine candidate met the criteria of Ph. Eur Monograph 0065, Swine-fever vaccine (live, prepared in cell cultures), classical 7th Edition. Fulfilling these validity criteria is a key step in the registration procedure for a vaccine candidate.