Assessment of the Ecuadorian ECJB 2000 isolate of classical swine fever virus as challenge strain

Abstract

Classical swine fever (CSF) is an infectious disease responsible for high economic losses in pigs of all ages. Several programs for the control and eradication of this disease have been implemented at a global level, being vaccination the principal mechanism. This research had the purpose of identifying the pathogenicity of an isolated circulating strain in Ecuador, and determining the efficacy of the vaccine applied for prevention. Animals were challenged with decreasing doses of the viral strain ECJB 2000 to obtain 10 median infective doses of this strain in pigs (DI₅₀). Afterward, the efficacy of a vaccine of the lapinized Chinese strain was evaluated against the virus of porcine cholera adapted to a cell culture line derived from a miniature pig kidney (MPK-LC-HCV), averaging a trial potency following the standard protocol of the World Organization for Animal Health (OIE). The vaccine was applied at different dilutions, and 14 days later, a viral challenge was done with DI₅₀. The unimmunized pigs presented clinical signs from day three post-infection, and the statistical results did not show significant differences in the body temperature registers and leukocyte count. Spearman-Kärber’s trial determined that the vaccine contained 239.88 protective doses (DI₅₀); taking into account that an effective vaccine against classical swine fever virus (CSFV) must have a value of > 100. This study demonstrated that the circulating strain in Ecuador is of elevated pathogenicity and that the vaccine is effective for the control of the disease.