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 naïve to FHV-1 (n = 9 cats, 18 eyes; control population) and cats naturally exposed to FHV-1 (n = 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 t-tests and results are presented as mean ± standard deviation. Compared to control, herpetic cats had significantly higher (P ≤ 0.010) clinical scores (0.2 ± 0.4 vs. 4.6 ± 2.8) and response to nasolacrimal stimulation (7.8 ± 10.8% vs. 104.8 ± 151.1%), significantly lower (P < 0.001) corneal sensitivity (2.9 ± 0.6 cm vs. 1.4 ± 0.9 cm), STT-1 (20.8 ± 2.6 mm/min vs. 10.6 ± 6.0 mm/min), TFBUT (12.1 ± 2.0 s vs. 7.1 ± 2.9 s), and non-significantly lower blink rate (3.0 ± 1.5 blinks/min vs. 2.7 ± 0.5 blinks/min; P = 0.751). All parameters evaluated for corneal nerves (e.g., nerve fiber length, branching, occupancy) were notably but not significantly lower in herpetic vs. control cats (P ≥ 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 naïve to the virus. It is possible these are signs of metaherpetic disease as reported in other species.
Highlights
IntroductionCorneal nerves play a critical role in maintaining ocular surface health and homeostasis, providing sensory stimuli for ocular protection (blinking) and lubrication (tear secretion), as well as trophic factors to promote epithelial integrity and corneal wound healing [1, 2]
Corneal nerves play a critical role in maintaining ocular surface health and homeostasis, providing sensory stimuli for ocular protection and lubrication, as well as trophic factors to promote epithelial integrity and corneal wound healing [1, 2]
Several local and systemic etiologies can compromise corneal innervation in humans and veterinary species, including diabetes mellitus, dry eye, surgery, and ocular infections [1, 5,6,7]. The latter is wellrecognized for viruses belonging to the Herpesviridae family given their neurotropic nature and lifelong persistence in the sensory neurons, with herpes simplex virus-1 (HSV-1) disrupting corneal innervation in humans [8,9,10,11] and canine herpesvirus1 (CHV-1) recently associated with corneal hypoesthesia in a dog with protracted corneal disease [12]
Summary
Corneal nerves play a critical role in maintaining ocular surface health and homeostasis, providing sensory stimuli for ocular protection (blinking) and lubrication (tear secretion), as well as trophic factors to promote epithelial integrity and corneal wound healing [1, 2]. Several local and systemic etiologies can compromise corneal innervation in humans and veterinary species, including diabetes mellitus, dry eye, surgery, and ocular infections [1, 5,6,7]. The latter is wellrecognized for viruses belonging to the Herpesviridae family given their neurotropic nature and lifelong persistence in the sensory neurons, with herpes simplex virus-1 (HSV-1) disrupting corneal innervation in humans [8,9,10,11] and canine herpesvirus (CHV-1) recently associated with corneal hypoesthesia in a dog with protracted corneal disease [12]. Uhl et al recently described the clinical features of aqueous tear deficiency in cats, reflecting on herpesvirus-related neuropathy as a potential etiology for dry eye given the lack of therapeutic response to immunomodulatory drugs; the association with FHV-1 and corneal innervation was not investigated in that retrospective case series [16]
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