Approved and experimental countermeasures against pestiviral diseases: Bovine viral diarrhea, classical swine fever and border disease

The pestiviruses, bovine viral diarrhea virus (BVDV), classical swine fever (CSFV) and border disease virus, are important livestock pathogens in many countries, but current vaccines do not completely prevent the spread of infection. Control of pestiviral diseases is especially difficult due to the constant viremia and viral shedding of persistently infected (PI) animals, which must be identified and eliminated to prevent disease transmission. Existing vaccines are limited by the delay between vaccination and the onset of protection, the difficulty of differentiating serologically between vaccinated and naturally infected animals and the need for broad vaccine cross-protection against diverse virus strains. Antiviral therapy could potentially supplement vaccination by providing immediate protection in the case of an outbreak. Numerous compounds with in vitro antiviral activity against BVDV have been identified through its role as a surrogate for hepatitis C virus. Fewer drugs active against CSFV have been identified, but many compounds that are effective against BVDV will likely inhibit CSFV, given their similar genomic sequences. While in vitro research has been promising, the paucity of efficacy studies in animals has hindered the commercial development of effective antiviral drugs against the pestiviruses. In this article, we summarize the clinical syndromes and routes of transmission of BVD, CSF and border disease, discuss currently approved vaccines, review efforts to develop antiviral therapies for use in outbreak control and suggest promising directions for future research.