Keratoconjunctivitis in a group of Icelandic horses with suspected c-herpesvirus involvement J. O. RUSHTON, J. KOLODZIEJEK † , B. NELL, H. WEISSENB € OCK ‡ and N. NOWOTNY* †§ Department of Companion Animals and Horses, University of Veterinary Medicine Vienna, Austria † Institute of Virology, University of Veterinary Medicine Vienna, Austria ‡ Institute of Pathology and Forensic Veterinary Medicine, University of Veterinary Medicine Vienna, Austria § Department of Microbiology and Immunology, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman. *Correspondence emails: nowotny@squ.edu.om; norbert.nowotny@vetmeduni.ac.at; Received: 07.02.15; Accepted: 26.05.15 Summary Reasons for performing study: The role of equid c-herpesviruses on ocular surface diseases has been disputed, because the diagnosis is usually based on clinical symptoms and detection of viral DNA from samples obtained from live animals. Objectives: To describe the clinical course, results of polymerase chain reaction (PCR) analysis, in situ hybridisation, cell culture and pathohistological ﬁndings of select cases in a presumed outbreak of herpesvirus infection in a group of 15 Icelandic horses. Study design: Case series. Methods: Pooled ocular and nasal swabs and peripheral blood mononuclear cells of horses diagnosed clinically with herpesvirus-associated keratoconjunctivitis were analysed for presence of equine herpesviruses (EHV)-2 and EHV-5 nucleic acid using real-time PCR. Necropsy specimens from one horse, subjected to euthanasia due to deterioration of clinical symptoms were examined histopathologically, and analysed for presence of EHV-2 and EHV-5 nucleic acid using real-time PCR. In situ hybridisation and cell culture of select samples were performed. Results: All horses with symptoms of severe keratoconjunctivitis were positive for presence of either EHV-2 and/or EHV-5 nucleic acid using real-time PCR. Assessment of necropsy specimens of the most severely affected case, revealed presence of EHV-2 and/or EHV-5 nucleic acid in several ocular and extraocular anatomical locations. The remaining horses responded favourably to symptomatic treatment. Conclusions: This case series illustrates a severe outbreak of keratoconjunctivitis in a group of Icelandic horses, with suspected c-herpesvirus involvement. For the ﬁrst time equid c-herpesviruses were detected in intraocular anatomical locations. Keywords: horse; EHV-2; EHV-5; gammaherpesviruses; Icelandic horse; keratoconjunctivitis Introduction Since the ﬁrst reports of outbreaks of equid herpesvirus-2 (EHV-2) induced keratoconjunctivitis in horses [1,2], the role of c-herpesviruses on the development of ocular disease has been subject to extensive investigation [3–8]. However, to date the exact pathogenesis of herpesvirus induced keratoconjunctivitis is undetermined. The ubiquitous nature and the potential for latent infection of c-herpesviruses, as well as the inﬂuence of host immune response on the development of clinical disease, render experimental studies difﬁcult to perform [3,4,9,10]. However, despite the drawbacks in experimental studies, the inﬂuence of c-herpesviruses on the development of ocular diseases cannot be disregarded. Clinical history An outbreak of sudden-onset keratoconjunctivitis in a group of 15 Icelandic horses aged between approximately one and 3 years was reported to the ophthalmology unit of the University of Veterinary Medicine Vienna. Symptomatic treatment with topical antibiotics (not speciﬁed) and systemic nonsteroidal anti-inﬂammatory drugs (NSAIDs; not speciﬁed) was initiated by the referring veterinarian. Physical examination and ophthalmological ﬁndings All horses had mucopurulent ocular, nasal discharge and corneal oedema of various severity. Corneal ulceration was not detected by uptake of ﬂuorescein stain at the time of initial examination in any horse. Horses more severely affected showed blepharospasm. All animals were reported to have been febrile, but no fevers were detected, presumably due to the systemic administration of NSAIDs. The remainder of the complete physical examination of the animals was within normal limits. Laboratory investigations Due to the large number of affected animals and ﬁnancial constraints of the owners, ocular and nasal swabs and whole blood of only the ﬁve most severely affected animals were obtained and submitted for further diagnostic work-up. Based on the course of disease and the clinical presentation a viral agent was suspected. Conjunctival swabs were taken from the most severely affected horse and submitted for bacterial and fungal cultures, revealing moderate amounts of commensal bacterial and fungal ﬂora with no predominant microbial agents. Extracted DNA samples of ocular and nasal swabs and peripheral blood mononuclear cells of each horse were pooled and analysed for the presence of EHV-2 using methods described in earlier reports [3]. All horses were positive for EHV-2 with real- time polymerase chain reaction (PCR) analysis. Treatment and clinical progress All horses were treated with topical triﬂuridine (Virophtha a ) t.i.d. Re-evaluation of affected animals 1 week later revealed marked improvement of ocular signs. Treatment, however, was continued. Re-examination of the horses 2 weeks after initial presentation revealed signiﬁcant improvement in all horses except one, which had developed bilateral melting corneal ulcers in the temporal half of the cornea (Fig 1). This animal was hospitalised on the same day. Cytology of ocular scrapings was performed to rule out the presence of fungal or bacterial pathogens. No intracellular bacteria or fungal hyphae were identiﬁed upon cytology. Treatment consisted of systemic NSAIDs (Finadyne b 1.1 mg/kg bwt s.i.d.), as well as topical serum and EDTA every other hour, topical triﬂuridine, natamyicin (Infektomyk c ), neomycin-polymyxin-bacitracin (Polyspektran d ) six times daily and topical atropine (Atropin e ) s.i.d. Due to ﬁnancial constraints bilateral placement of conjunctival pedical grafts was not an option. Despite intensive treatment over 10 days, there was no signiﬁcant improvement and the horse was subjected to euthanasia. Equine Veterinary Journal 48 (2016) 427–429 © 2015 EVJ Ltd 427 Equine Veterinary Journal ISSN 0425-1644 DOI: 10.1111/evj.12465