Three Novel Herpesviruses of Endangered Clemmys and Glyptemys Turtles

Abstract

The rich diversity of the world’s reptiles is at risk due to significant population declines of broad taxonomic and geographic scope. Significant factors attributed to these declines include habitat loss, pollution, unsustainable collection and infectious disease. To investigate the presence and significance of a potential pathogen on populations of critically endangered bog turtles (Glyptemys muhlenbergii) as well sympatric endangered wood (G. insculpta) and endangered spotted (Clemmys guttata) turtles in the northeastern United States, choanal and cloacal swabs collected from 230 turtles from 19 sites in 5 states were screened for herpesvirus by polymerase chain reaction. We found a high incidence of herpesvirus infection in bog turtles (51.5%; 105/204) and smaller numbers of positive wood (5) and spotted (1) turtles. Sequence and phylogenetic analysis revealed three previously uncharacterized alphaherpesviruses. Glyptemys herpesvirus 1 was the predominant herpesvirus detected and was found exclusively in bog turtles in all states sampled. Glyptemys herpesvirus 2 was found only in wood turtles. Emydid herpesvirus 2 was found in a small number of bog turtles and a single spotted turtle from one state. Based on these findings, Glyptemys herpesvirus 1 appears to be a common infection in the study population, whereas Glyptemys herpesvirus 2 and Emydid herpesvirus 2 were not as frequently detected. Emydid herpesvirus 2 was the only virus detected in more than one species. Herpesviruses are most often associated with subclinical or mild infections in their natural hosts, and no sampled turtles showed overt signs of disease at sampling. However, infection of host-adapted viruses in closely related species can result in significant disease. The pathogenic potential of these viruses, particularly Emydid herpesvirus 2, in sympatric chelonians warrants additional study in order to better understand the relationship of these viruses with their endangered hosts.

Epidemiology of Emydoidea Herpesvirus 1 in Free-Ranging Blanding's Turtles (Emydoidea Blandingii) From Illinois

“…All currently recognized reptilian herpesviruses belong to the subfamily Alphaherpesvirinae and chelonian herpesviruses are the best characterized of these (Wellehan and Johnson 2005;Ariel 2011;Marschang 2011;Wellehan 2012). Chelonian herpesviruses form a monophyletic cluster consistent with a genus, which has been called Chelonivirus Ossiboff et al 2015b), Glyptemys herpesvirus 1 and 2 (Ossiboff et al 2015b), and Terrapene herpesvirus 1 and 2 (Sim et al 2015;Yonkers et al 2015). Given the degree of relatedness and clinical similarities between Testudinid and Emydid herpesviruses and their hosts, the majority of discussion in this thesis will focus on these viruses.…”

“…Skin lesions represent a different clinical presentation in Emydids, including hyperkeratosis in an Australian Krefft's river turtle (Emydura macquarii krefftii) infected with an uncharacterized herpesvirus (Cowan et al 2015) and fibropapilloma in an Eastern box turtle infected with Terrapene herpesvirus 2 (Yonkers et al 2015). Mortalities without premonitory clinical signs (Jungwirth et al 2014) and infection in apparently healthy individuals (Ossiboff et al 2015a(Ossiboff et al , 2015bKane et al 2017) have been reported in Emydids. Interestingly, painted turtles (Chrysemys picta) have been implicated as possible asymptomatic carriers or a reservoir for Emydid herpesvirus 1 after being found in four apparently healthy individuals housed in the same system as a Northern map turtle (Graptemys geographica) that died with herpesvirus inclusions in the liver, lung, and spleen (Ossiboff et al 2015a).…”

“…Most importantly, herpesviruses have recently been identified to be widespread in apparently healthy free-ranging Emydid chelonian populations, however, the clinical significance of this finding in the absence of an outbreak is currently unknown (Ossiboff et al 2015b;Kane et al 2017). Consensus PCR of combined choana-cloaca swabs was used to identify Glyptemys herpesvirus 1 in 48.5% of sampled bog turtles (Glyptemys muhlenbergii) (n=204) from five northeastern states; Glyptemys herpesvirus 2 in 55.6% of wood turtles (Glyptemys insculpta) (n=9) from two states; and Emydid herpesvirus 2 in 2.9% of bog turtles (n=204) and 5.9% spotted turtles (Clemmys guttata) (n=17) (Ossiboff et al 2015b). Sampling was conducted in spring of 2011, 2013, and 2014 during this study.…”

“…Sampling was conducted in spring of 2011, 2013, and 2014 during this study. None of the turtles showed clinical signs of herpesvirus infection (Ossiboff et al 2015b). Finally, an epidemiologic investigation using a Terrapene herpesvirus-specific quantitative PCR (qPCR) assay was recently conducted in free-ranging Eastern box turtles from Tennessee and Illinois in two consecutive years (Kane et al 2017).…”

“…Although the vast majority of literature demonstrating the clinical presentation and disease progression of herpesviruses in chelonians is derived from captive tortoises and turtles (Tables 2.1 and 2.2), herpesviruses have also been identified in apparently healthy free-ranging Testudinids and Emydids (Ossiboff et al 2015b;Kane et al 2017). The clinical signs of herpesvirus infection vary by host species and virus, but upper respiratory signs and necrotizing stomatitis has been frequently reported (Tables 2.1 and 2.2).…”