The prevalence of DNA of EHV-2 and EHV-5 in horses with keratokonjunctivitis and clinically normal horses in Switzerland

Abstract

ZusammenfassungNicht alle als viral betrachteten Keratitiden lassen sich mittels PCR auf EVH-2 oder EHV-5 zurückführen. Ziel der Untersuchung war deshalb der Vergleich der Prävalenz von EHV-2 und EHV-5 mittels PCR bei Pferden mit Keratokonjunktivitis und augengesunden Pferden. Zytologische Hornhautproben von 131 Pferden mit einer vermuteten viralen Keratokonjunktivitis zwischen 2001 und 2010, sowie von 163 augengesunden Pferden von 3 verschiedenen Beständen wurden mittels PCR auf EHV-2 und EHV-5 untersucht. Die Prävalenz von EHV-2 und 5 unterscheidet sich nicht signifikant bei augengesunden Pferden und solchen mit Keratokonjunktivitis. Es konnten keine spezifischen ophthalmologischen Symptome dem einen oder anderen Virustyp zugeordnet werden. Das klinische Bild einer Keratitis punctata, welches als typisch für virale Keratitiden betrachtet wird, wurde bei beiden Virustypen beobachtet. Es scheint als ob Infektionen mit EHV-5 nur milde Symptome verursacht, verglichen mit Infektionen mit EHV-2. Die schwersten klinischen Symptome traten bei Doppelinfektionen mit EHV-2 und 5 auf. In dieser Untersuchung konnte kein signifikanter Prävalenzunterschied von EHV-2 und 5 zwischen beiden Gruppen festgestellt werden. Die Pathogenität von EHV-2 und 5 bleibt unklar, ist jedoch sicher nicht als hochgradig einzustufen.Schlüsselwörter: Pferd / Keratokonjunktivitis / Ätiologie / Equines Herpesvirus / Prävalenz / Ophthalmologie The prevalence of DNA of EHV-2 and EHV-5 in horses with keratokonjunctivitis and clinically normal horses in SwitzerlandNot all viral keratoconjunctivitis can be detected by PCR as caused by EHV-2 and 5. The authors therefore compared the prevalence of EHV-2 and 5 by PCR in horses with keratoconjunctivitis and healthy horses. Conjunctival cytobrush samples of 131 horses with suspected viral keratoconjunctivitis between 2001 and 2010 and of 163 healthy horses from three different stables were tested by PCR for the presence of EHV-2 and EHV-5. The prevalence of EHV-2 and 5 is not significantly different in healthy horses and horses with keratoconjunctivitis. No specific ophthalmic signs could be attributed to either EVH-2 or EHV-5. The punctate pattern on the corneal surface, which is considered typical for a viral keratitis, was found in horses infected with EHV-2 or EHV-5. It appears, that an EHV-5-infection causes only mild clinical signs compared to horses testing positive for EHV-2. The most severe clinical signs were seen in horse testing positive for EHV-2 and 5. In this investigation the prevalence of EHV-2 and EHV-5 was similar in healthy horses and horses with keratoconjunctivitis. No statistically significant differences were found. The pathogenicity of EHV-2 and 5 is not clear or very weak.

Gammaherpesvirus infections in equids: a review

“…Although EHV-2 has been associated with conjunctivitis in horses of all ages, viral antigen has also been detected in the conjunctiva of clinically healthy horses. 54 , 61 , 75 , 98 , 111 – 115 The cells that EHV-2 targets in the conjunctiva of healthy horses have been identified as histiocyte-like cells located in the submucosa, particularly Langerhans cells. 98 The combined evidence from natural and experimental infections and the success of antiviral therapy in a cohort study would support a role for EHV-2 in the pathogenesis of keratoconjunctivitis in foals and adult horses, 54 , 61 , 116 and yearlings following immunosuppressive doses of dexamethasone.…”

“… 22 , 53 , 66 , 84 , 99 , 100 , 118 , 134 , 135 The role of the virus in ocular disease has not been defined. 61 , 113 , 115 A case of dermatitis, similar to herpes-associated erythema multifor me in humans, has been described in association with EHV-5. 136 Moreover, EHV-5 DNA has been found in uterine flushings, 121 aborted fetuses, and cases of neonatal mortality.…”

Multiplex real-time PCR for the detection and differentiation of equid gammaherpesvirus 2 and 5

“…EHV-2 and EHV-5 have been linked to several rather mild disease patterns, including respiratory signs like fever, coughing and nasal discharge (Dunowska et al, 2002b(Dunowska et al, , 1999El-Hage et al, 2016;Murray et al, 1996;Wang et al, 2007), pharyngitis and enlarged lymph nodes (Blakeslee et al, 1975) and poor performance (Hue et al, 2014;Mumford and Rossdale, 1980). In addition, both viruses were detected in conjunctival swabs from horses suffering from keratitis, keratouveitis and keratoconjunctivitis (Borchers et al, 2006b;Kershaw et al, 2001;Krisová et al, 2020;Krüdewagen et al, 2001;Rushton et al, 2016Rushton et al, , 2013Sonderegger et al, 2013). Recently, there has been increasing evidence that EHV-5 plays a causative role in equine multinodular pulmonary fibrosis (EMPF), a progressive and lethal interstitial lung disease in adult horses (Williams et al, 2007).…”

“…Despite frequent detection of both EHV-2 and EHV-5 in diseased horses, the exact significance attributed to the two gammaherpesviruses is not yet fully understood, as the viruses are also regularly detected in healthy horses (Bell et al, 2006;Borchers et al, 2006aBorchers et al, , 1997Krüdewagen et al, 2001;Marenzoni et al, 2010;Murray et al, 1996;Nordengrahn et al, 2002;Rushton et al, 2013;Scheurer et al, 2021;Sonderegger et al, 2013;Stasiak et al, 2022). A co-factor role in the pathogenesis of pulmonary fibrosis, as described for human Epstein-Barr virus, would be conceivable (Williams, 2014).…”