Diphenyl diselenide and cidofovir present anti-viral activity against Bovine Alphaherpesvirus 2 in vitro and in a sheep model.

Bovine alphaherpesvirus 2 (BoHV-2) - the agent of bovine herpetic mamillitis (BHM) - is related to Human alphaherpesviruses 1 and 2 (HHV-1, HHV-2) and, as such, has been proposed as a model for vaccine and drug testing. We herein investigated the anti-viral activity in vitro against BoHV-2 of three anti-herpetic drugs: Cidofovir (CDV), Fanciclovir (FAM), Foscarnet (PFA), and diphenyl disselenide (PhSe) a compound that has showed activity against HHV-2. Plaque reduction assays (PRA) revealed a significant reduction in viral plaques (p < 0.05) in cells treated with PhSe (79.7% reduction) or CDV (62.8%). FAM treatment resulted in a slight decrease in plaque number (22.9%, p < 0.05); PFA showed no activity. The effects of PhSe and CDV, alone or in combination, were investigated in ewes inoculated with BoHV-2 transdermally and submitted to daily topic treatment. Virus inoculated ewes developed lesions progressing through the stages of hyperemia, large papules or depressed dark areas, followed by scab formation. Treatment with PhSe resulted in reduction in clinical score from day 10 pi onwards (P < 0.05), shortening of clinical course and reduction in duration of virus shedding (P < 0.05) compared to untreated controls. Combined treatment (PhSe + CDV) and CDV alone, also led to clinical improvement (P < 0.05), yet less pronounced and delayed. These results are promising towards the use of PhSe, alone or in combination with anti-herpetic drugs, in the treatment of udder and teat lesions produced by BoHV-2 in dairy cows.