Herpesvirus skin disease in free-living common frogs Rana temporaria in Great Britain

Abstract

Infectious disease is a significant driver of global amphibian declines, yet despite this, relatively little is known about the range of pathogens that affect free-living amphibians. Recent detection of the tentatively named Ranid herpesvirus 3 (RHV3), associated with skin disease in free-living common frogs Rana temporaria in Switzerland, helps to address this paucity in knowledge, but the geographic distribution and epidemiology of the pathogen remains unclear. Syndromic surveillance for ranid herpesvirus skin disease was undertaken throughout Great Britain (GB), January 2014 to December 2016. Reports of common frogs with macroscopic skin lesions with a characteristic grey appearance were solicited from members of the public. Post-mortem examination was conducted on one affected frog found dead in 2015 at a site in England. In addition, archived samples from an incident involving common frogs in England in 1997 with similar macroscopic lesions were further investigated. Transmission electron microscopy identified herpes-like virions in skin lesions from both the 1997 and 2015 incidents. RHV3, or RHV3-like virus, was detected in skin lesions from the 2015 case by PCR and sequencing. Our findings indicate that herpesvirus skin disease is endemic in common frogs in GB, with widespread distribution at apparently low prevalence. Further research into the role of host immunity, virus latency and the significance of infection to host survival is required to better understand the epidemiology and impact of cutaneous herpesvirus infections in amphibian populations.

Emerging infectious disease threats to European herpetofauna

“…These are the first amphibian herpesviruses outside of North America to be fully characterised and described in wild caught amphibians. Additionally, Franklinos et al (2018) found herpesvirusassociated dermatitis in common toads. However, the virus(es) present in UK amphibians was/were not fully characterised, so it is unknown if two different virus species are present.…”

“…The gross clinical signs of amphibian herpesvirus infections appear to be conserved across affected species. Typically, lesions are present on the skin that may be tan (more terrestrial species), grey, or grey-blue in colour (typical of more aquatic species; see Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018). These are areas where the skin has become thickened and they may appear on any region of the body (Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018).…”

“…Typically, lesions are present on the skin that may be tan (more terrestrial species), grey, or grey-blue in colour (typical of more aquatic species; see Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018). These are areas where the skin has become thickened and they may appear on any region of the body (Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018). The number of lesions that appear on the skin of affected animals is often variable, ranging from one to covering most of the skin (Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018;Fig.…”

“…These are areas where the skin has become thickened and they may appear on any region of the body (Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018). The number of lesions that appear on the skin of affected animals is often variable, ranging from one to covering most of the skin (Origgi et al, 2017;Franklinos et al, 2018;Origgi et al, 2018;Fig. 6).…”

“…Duffus and Cunningham (2010) reviewed two major disease threats to European amphibians, Batrachochytrium dendrobatidis (Bd) and ranaviruses. Since the publication of that review, other emerging infectious diseases in European amphibian populations have been identified, B. salamandrivorans (Bsal, Martel et al, 2013), and the potentially emerging amphibian herpesviruses (Franklinos et al, 2018;Origgi et al, 2017). In reptiles, the emergence of two troubling infectious diseases has also been documented in wild populations, snake fungal disease (Ophidiomyces ophiodiicola, Franklinos et al, 2017) and ranaviruses (Alves de Matos et al, 2011).…”