New Strategies for the Management of Acute Feline Herpesvirus 1 Conjunctivitis and Chronic Feline Calicivirus Associated Stomatitis

Abstract

Viruses that establish a lifelong latency in cats pose a unique challenge for veterinarians in terms of management and treatment. Feline herpesvirus-1 (FHV) and feline calicivirus (FCV) are 2 such viral triggers for upper respiratory tract infections and are estimated to impact much of the global domestic feline population. The highly contagious and potentially virulent nature of these 2 viruses has led to an interest in the development of therapeutics that can be administered to limit recrudescence phases and potentially inhibit viral replication altogether.Despite a differing viral trigger, cats impacted by these viruses may have a degree of immune dysfunction that occurs, enabling more serious manifestations of clinical presentation. The potential for immune dysregulation occurring in these cats highlights an opportunity to explore the effects of immunotherapy treatments, allowing for the body to mount its own immune defenses as opposed to administering a therapy that may have potential side effects. The objectives for Chapter 1 were to find if a lower FHV-1 initial inoculation dose could elicit a similar clinical presentation to cats inoculated with the current approved USDA FHV-1 dose for potential use in future immunotherapy studies, assess whether an ocularly administered immunotherapy (LTAC) could be an effective treatment for FHV-1 associated conjunctivitis when compared to artificial tears, and to determine if the administration of a short course antiviral (Cidofovir) was effective in reducing conjunctivitis in cats with persistent FHV-1 associated conjunctivitis. We found that there was no difference in clinical presentation between FHV-1 inoculation doses, indicating that this lower dose may be more effective when studying FHV-1 in immunotherapy models. In applying this lower inoculation dose, there was no difference in conjunctivitis resolution between cats administered an ocular immunotherapy versus artificial tears. Cidofovir, however, was effective in resolving FHV-1 associated conjunctivitis in a short-term protocol. The findings from Chapter 1 may be used to design future FHV-1 investigations in addition to furthering our understanding of immunotherapies for the treatment of FHV-1. In Chapter 2, we explored the effect of orally administered LTAC on cats with FCV associated feline chronic gingivostomatitis (FCGS). We found that 50% of the cats in the study had improvements in both clinical signs and oral inflammation, and both cats that responded and did not respond clinically had changes to their production of interferons and FCV viral load. The findings from Chapter 2 indicate an immune response was elicited in some of the cats, which should be further explored in future investigations to determine whether immunotherapies may be effective in cats with FCV associated FCGS.