Effect of FHV-1 Inoculation Dose on Clinical Presentation and Subsequent Responses to a Topical Immunotherapeutic or Cidofovir

Feline herpesvirus type-1 (FHV-1) is a common viral agent associated with respiratory and ocular infections in cats. Many experimental FHV-1 challenge studies utilize the United States Department of Agriculture (USDA) strain and challenge dose developed for vaccine challenge studies. However, those FHV-1 challenge doses are likely to be considerably higher than what may be acquired naturally, potentially leading to unrepresentative results for studies other than vaccine studies. The objectives of this study were therefore to compare clinical responses to the standard FHV-1 challenge dose with those to a significantly lower challenge in naïve kittens. Secondly, the study assessed and compared clinical responses in the high- and low-dose challenge models to either a nonspecific immune stimulant or to the antiviral drug cidofovir. We found that there were no significant differences in clinical scores between high- and low-dose challenge FHV-1 groups. In addition, cats in the two dose groups responded similarly to the nonspecific immunotherapy or to cidofovir treatment. Thus, we concluded that the lower-dose challenge may be more effective for screening new drugs or vaccines for FHV-1 ocular infections in cats.