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

This research examines how long equine herpesvirus-4, feline herpesvirus-1, and feline calicivirus live in three different ophthalmic solutions commonly used for eye irritations in animals.

Research Methodology

• The researchers used three specific viruses that were originally isolated from the eyes of animals referred to the University of Illinois. These viruses were equine herpesvirus-4, feline herpesvirus-1, and feline calicivirus. The equine herpesvirus was grown in MDBK cells, while the feline viruses were propagated in CRFK cells.
• The study method involved inoculating each ophthalmic solution with a specific titer of each virus. These solutions were then stored according to the manufacturer’s instructions at either 4 degrees Celsius or 25 degrees Celsius.
• The virus titers within the solutions were measured at several intervals – 1, 8, and 24 hours, and then 3, 5 and 7 days after inoculation. The measurement was done using either plaque or TCID50 assays.

Research Findings

• The three viruses under study remained present in eyewash for different durations. The equine herpesvirus and feline calicivirus lasted for 7 days, while the feline herpesvirus lasted for 5 days. The eyewash did not lessen the survival time of any virus as compared to controls.
• In the fluorescein solution, both the equine herpesvirus and feline herpesvirus (which are enveloped viruses) were not recoverable after 1 hour of inoculation. On the other hand, the feline calicivirus (a non-enveloped virus) survived in the solution for 7 days.
• In the proparacaine solution, the equine herpesvirus and feline herpesvirus also did not remain infectious past the 1-hour mark post inoculation. However, the feline calicivirus could be recovered up to 24 hours post-inoculation.

Conclusions from the Study

• The study suggests that these three viruses can be easily transmitted through the eyewash solution tested. Hence, there may be a risk of iatrogenic (caused by medical examination or treatment) transmission of these viruses through the use of these ophthalmic solutions.
• The risk of such transmission was significantly reduced in both the fluorescein and proparacaine solutions. Notably, the feline calicivirus, the only non-enveloped virus in the study, remained viable longer in both these solutions.