Evaluation of the transmission of porcine circovirus type 2 (PCV-2) genogroups a and b with semen from infected specific-pathogen-free boars

Abstract

The porcine circovirus type 2 (PCV-2) is associated with several diseases including reproductive failure. This syndrome has been experimentally reproduced twice with two PCV-2 isolates representative of each major PCV-2 genogroup, i.e. PCV-2a and PCV-2b (Cariolet et al., 2002; Rose et al., 2007). In these two previous studies, the sows were infected by intra-uterine inoculation at insemination with 104.3 and 103.18 TCID50 of PCV-2a and PCV-2b, respectively, corresponding to 1.2×1011 and 3×1010 genome copies, respectively.The aim of this present study was to quantify viral shedding in semen from specific-pathogen-free (SPF) boars infected with isolates from the two major PCV-2 genogroups a and b. We studied the transmission of the PCV-2 virus through contaminated semen to SPF sows and their offspring. The four inoculated boars developed sub-clinical PCV-2 infections and PCV-2 genomes were occasionally detected in semen after nasal infection of boars, with up to 1.2×106copies/mL in the sperm-rich fraction. When PCV-2-contaminated semen was inoculated in SPF sows at artificial insemination, the sows and their offspring did not show any signs of PCV-2 infection or PCV-2 antibodies or genomes. In the present study, sows were inoculated with a maximal dose of 1.7×107 viral genome copies, which is lower than the genomic loads (i.e. 1.2×1011 and 3×1010 genome copies) that have been shown to induce reproductive troubles in intra-uterine inoculated sows. Our results together with the previous experiment findings suggest that PCV-2-induced reproductive disorders depend on the infectious dose inoculated to sows by the intra-uterine route.