Vaccination of Sheep with Bovine Viral Diarrhea Vaccines Does Not Protect against Fetal Infection after Challenge of Pregnant Ewes with Border Disease Virus.

Gilles Meyer,Mickael Combes,Angelique Teillaud,Herve Cassard,Celine Pouget,Marie-Anne Bethune

doi:10.3390/vaccines9080805

Abstract

Border Disease (BD) is a major sheep disease characterized by immunosuppression, congenital disorders, abortion, and birth of lambs persistently infected (PI) by Border Disease Virus (BDV). Control measures are based on the elimination of PI lambs, biosecurity, and frequent vaccination which aims to prevent fetal infection and birth of PI. As there are no vaccines against BDV, farmers use vaccines directed against the related Bovine Viral Diarrhea Virus (BVDV). To date, there is no published evidence of cross-effectiveness of BVDV vaccination against BDV infection in sheep. We tested three commonly used BVDV vaccines, at half the dose used in cattle, for their efficacy of protection against a BDV challenge of ewes at 52 days of gestation. Vaccination limits the duration of virus-induced leukopenia after challenge, suggesting partial protection in transient infection. Despite the presence of BDV neutralizing antibodies in vaccinated ewes on the day of the challenge, fetuses of vaccinated and unvaccinated sheep were, two months after, highly positive for BDV RNA loads and seronegative for antibodies. Therefore, BVDV vaccination at half dose was not sufficient to prevent ovine fetal infection by BDV in a severe challenge model and can only be reconsidered as a complementary mean in BD control.

Highlights

The Pestivirus genus within the Flaviviridae family comprises eleven recognized species, named from A to K [1]
It was previously shown to belong to Border Disease Virus (BDV) genotype 6 and to successfully produce 100% persistently infected (PI) lambs when inoculated to naïve ewes at 52 days of gestation [12]
The BDV-6 detection in the blood of unvaccinated ewes after infection and their seroThe BDV-6 detection in the blood of unvaccinated ewes after infection and their seconversion validate the model used in this study

Summary

Introduction

The Pestivirus genus within the Flaviviridae family comprises eleven recognized species, named from A to K [1]. Disease Virus (BDV, Pestivirus D) belongs to one of the 4 main viral species recognized within this genus. BDV is responsible for Border Disease (BD), which is primarily an infection of sheep and rarely of goats and cattle, characterized by immunosuppression and increased risk of other infections, congenital disorders, abortion, stillbirths, and the birth of weak lambs persistently infected (PI animals) experiencing tremors, abnormal body conformation, and hairy fleece [2]. Control measures have been put in place by the breeders’ associations to limit BD spread [6]. These measures are traditionally based on the detection and elimination of PI lambs, biosecurity measures, and vaccination. Vaccination is currently used alone, mainly because there is no substantial financial support for PI animals’ detection and elimination

Methods

Results

Conclusion