Altered Corneal Innervation and Ocular Surface Homeostasis in FHV-1-Exposed Cats: A Preliminary Study Suggesting Metaherpetic Disease.

Abstract

Metaherpetic disease is recognized in humans affected by herpes simplex virus-1 but is not reported in cats affected by feline herpesvirus-1 (FHV-1) despite the high prevalence of herpetic disease in this species and strong similarities in viral biology between alphaherpesviruses of humans and cats. This preliminary work evaluated cats na&#xef;ve to FHV-1 (= 9 cats, 18 eyes; control population) and cats naturally exposed to FHV-1 (= 4 cats, 7 eyes), as confirmed by serologic testing and review of medical records. Antemortem assessment included clinical scoring, blink rate, corneal aesthesiometry, tear film breakup time (TFBUT), and Schirmer tear test-1 (STT-1) with or without the nasolacrimal reflex. Post-mortem assessment involved confocal microscopy of the corneas and evaluation of corneal nerves with ImageJ. Groups were compared with Student's-tests and results are presented as mean &#xb1; standard deviation. Compared to control, herpetic cats had significantly higher (&#x2264; 0.010) clinical scores (0.2 &#xb1; 0.4. 4.6 &#xb1; 2.8) and response to nasolacrimal stimulation (7.8 &#xb1; 10.8%. 104.8 &#xb1; 151.1%), significantly lower (< 0.001) corneal sensitivity (2.9 &#xb1; 0.6 cm. 1.4 &#xb1; 0.9 cm), STT-1 (20.8 &#xb1; 2.6 mm/min. 10.6 &#xb1; 6.0 mm/min), TFBUT (12.1 &#xb1; 2.0 s. 7.1 &#xb1; 2.9 s), and non-significantly lower blink rate (3.0 &#xb1; 1.5 blinks/min. 2.7 &#xb1; 0.5 blinks/min;= 0.751). All parameters evaluated for corneal nerves (e.g., nerve fiber length, branching, occupancy) were notably but not significantly lower in herpetic. control cats (&#x2265; 0.268). In sum, cats exposed to FHV-1 had signs suggestive of corneal hypoesthesia and quantitative/qualitative tear film deficiencies when compared to cats na&#xef;ve to the virus. It is possible these are signs of metaherpetic disease as reported in other species.