Experimental infection of Bama miniature pigs with a highly virulent classical swine fever virus

Twenty specific-pathogen-free Bama miniature pigs were randomly divided into two groups and rooms, infected and non-infected, and the pigs in the infected group were inoculated intramuscularly with 104, 105 or 106 TCID50 (median tissue culture infective dose) CSFV Shimen strain (n = 5 × 3) or left uninoculated to serve as in-contact pigs (n = 3). The uninfected control pigs (n = 2) were housed in a separate room. Clinical signs, body temperature, viraemia, tissue antigen distribution, pathological changes and seroconversion were monitored. Clinical signs were observed as early as 2 days post-inoculation (dpi) in all infected pigs (though mild in contact pigs), but not non-infected control pigs. All inoculated pigs showed viraemia by 6 dpi. The in-contact pigs showed lower levels of viraemia. At 10 dpi, seroconversion was noted in five of the 15 inoculated pigs. All inoculated or one in-contact pigs died by 15 dpi.These results show that Bama miniature pigs support productive CSFV infection and display clinical signs and pathological changes consistent with CSFV infections observed in larger domestic pigs.Classical swine fever (CSF) is caused by classical swine fever virus (CSFV) and results in significant losses to the pig industry worldwide. CSFV belongs to the Pestivirus genus within the Flaviviridae family [1]. It is an enveloped virus containing a single-stranded, positive-sense RNA encoding a 3,898 amino acid polyprotein, which undergoes co- and post-translational processing by cellular and viral proteases to yield 11-12 cleavage products [2,3].Pigs are the natural host of CSFV, and are used as models for CSFV research. Therefore, vaccines against CSF should be evaluated exclusively in pigs in preclinical and clinical trials. A major challenge, however, is that domestic pigs are large and difficult to handle; thus, a convenient animal model is required for the study of CSF and other swine diseases. Several minipig strains, such as G？ttingen, CLAWN, Yucatan, Lan