Innocuity of a commercial live attenuated vaccine for epizootic hemorrhagic disease virus serotype 2 in late-term pregnant cows

Publication date: Available online 11 February 2016
Source:Vaccine
Author(s): Massimo Spedicato, Irene Carmine, Liana Teodori, Alessandra Leone, Ottavio Portanti, Valeria Marini, Maura Pisciella, Alessio Lorusso, Giovanni Savini
Epizootic hemorrhagic disease (EHD) is an arthropod-borne infectious non-contagious viral disease sustained by the epizootic hemorrhagic disease virus (EHDV). The only commercially available vaccines are manufactured for EHDV-2, either live or inactivated vaccines. In this study we wanted to test the innocuity for fetuses of a live attenuated EHDV-2 vaccine in five late-term pregnant cows. Whole blood and serum were regularly collected from dams and screened for the presence of EHDV-2 RNA, infectious virus and antibodies. After calving, whole blood and serum samples collected from calves, before and after colostrum intake, were tested for antibodies and for virus detection. In dams, neither fever nor clinical signs were observed. All of them seroconverted and a strong humoral response was detected throughout the sampling period. All blood samples tested negative for EHDV-2 except for one sample collected from a dam 11 days post-vaccination which tested positive at virus isolation at the third cell passage following two rounds of blind passages. Unexpectedly, although they had free access to colostrum, calves tested serologically negative for EHDV-2 during the entire course of the experiment. Overall, the tested live attenuated vaccine can be safely administered to late-term pregnant cows as it was not demonstrated to cross the placental barrier. The safety of the live-attenuated vaccine is further confirmed by the emergence of Ibaraki virus in 2013 in Japan which is not related to the vaccine strain used for decades in Japan.



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