Survival of equine herpesvirus-4, felyine herpesvirus-1, and feline calicivirus in multidose ophthalmic solutions

Objective: To determine survival over time of infectious equine herpesvirus-4, feline herpesvirus-1, and feline calicivirus in three commercially available and commonly used ophthalmic solutions (eyewash, fluorescein, and proparacaine HCl). Sample population: Viruses used in this study were originally isolated from eyes of animals referred to the University of Illinois. Equine herpesvirus-4 was propagated in MDBK cells and feline herpesvirus-1 and feline calicivirus in CRFK cells. Procedure: After separately inoculating a designated solution with a specific titer of an individual virus, solutions were incubated per manufacturer's recommendations, either at 4°C or 25°C. Virus titers within solutions were subsequently measured at 1, 8, and 24 h and 3, 5 and 7 days post inoculation using either plaque or TCID₅₀ assays. Results: Equine herpesvirus-4, feline herpesvirus-1, and feline calicivirus were present in eyewash for 7 days, 5 days, and 7 days, respectively. Eyewash did not decrease survival time of any virus when compared to controls. Equine herpesvirus-4 and feline herpesvirus-1, both enveloped viruses, were not recovered at any time ≥ 1 h post inoculation in fluorescein. Feline calicivirus, a nonenveloped virus, was present in fluorescein for 7 days. Equine herpesvirus-4 and feline herpesvirus-1 did not remain infectious in proparacaine at any time ≥ 1 h post inoculation, but feline calicivirus was recovered at up to 24 h post inoculation. Conclusions: Equine herpesvirus-4, feline herpesvirus-1, and feline calicivirus may be readily transmissible via the eyewash solution used in this study. Risk of iatrogenic transmission of the three viruses used in this study was significantly reduced in both fluorescein and proparacaine solutions. Feline calicivirus, the only nonenveloped virus evaluated, remained viable longer in both fluorescein and proparacaine solutions.