Herpesvirus associated dermal papillomatosis in Williams' mud turtle Pelusios williamsi with effects of autogenous vaccine therapy

Case report: Diagnosis and autogenous vaccine treatment of herpesvirus in a green turtle (Chelonia mydas) in Santa Marta, Colombia

This study reports the first case of fibropapillomatosis (FP) in the green turtle Chelonia mydas that has been successfully diagnosed and treated in Colombia. Worldwide, FP has reached epizootic proportions as it has been reported in marine turtles of tropical and subtropical waters, and in severe cases, it reduces the probability of survival. Treatment has been elusive as multiple surgical excisions are needed due to tumor recurrence. In this case, one green turtle with multiple tumors was diagnosed by histopathology and molecular detection of the chelonid herpesvirus 5 (ChHV5) by means of amplification and sequencing of the DNA polymerase (DNApol) gene. Two separate treatments that consisted of autogenous vaccines and surgical excisions were applied; the first one had a partial success as one out of the tumors treated reappeared after 3 months post-treatment. Treatment 2 consisted of an autogenous vaccine enriched with adjuvants and applied at increasing doses, after which, the tumor significatively decreased in size and was surgically removed. At the end of the 6 months follow-up period, no tumor recurrence was observed, and the turtle was in apparent optimal health conditions. These findings, although limited, suggest a possible treatment that might help to contain this epizootic problem.

Herpesviruses in Captive Chelonians in Europe Between 2016 and 2020

Herpesviruses are important pathogens in tortoises and turtles, yet little is known about the epidemiology of these viruses. We analyzed herpesviruses detected by PCR in samples from captive chelonians in Europe according to virus strain, host species, year and season in which the animal was tested, and country in which the animal was kept. A total of 4,797 samples submitted to a diagnostic laboratory in Europe between January 2016 and December 2020 were evaluated. Of these, 312 (6.50%) were positive for herpesviruses. The types most commonly found were testudinid herpesvirus (TeHV)1 (143 positive, 45.83%) and TeHV3 (153 positive, 49.04%), but also included TeHV2 (1 positive, 0.32%), TeHV4 (3 positive, 0.96%), Terrapene herpesvirus 1 (7 positive, 2.24%), Trachemys herpesvirus 1 (2 positive, 0.64%), and three previously undescribed herpesviruses (0.96%). Herpesviruses were detected in chelonians in the families Testudinidae, Emydidae, Geoemydidae, and in the suborder Pleurodira. Among the species for which 100 samples or more were available, the highest proportions of positive samples (positivity rates) were found in samples from Horsfield's tortoises (Testudo horsfieldii) (14.96%), and radiated tortoises (Astrochelys radiata) (14.05%). Among tortoises (Testudinidae), viruses were most often detected in the spring, while in emydid turtles (Emydidae) they were most often detected in the summer. A comparison of the positivity rates according to country showed significant differences, with the highest rate in samples from Italy (16.01%). This study indicated possible differences in herpesvirus positivity rates depending on host species, virus strain, year of sampling, season, and country of origin. It provides useful information in further understanding fluctuations in infection rates as well as in helping to guide decision making for herpesvirus diagnostics in chelonian patients. It also provides evidence for the international dispersal of herpesviruses with their hosts through international trade.

Herpesviruses in Reptiles

Since the 1970s, several species of herpesviruses have been identified and associated with significant diseases in reptiles. Earlier discoveries placed these viruses into different taxonomic groups on the basis of morphological and biological characteristics, while advancements in molecular methods have led to more recent descriptions of novel reptilian herpesviruses, as well as providing insight into the phylogenetic relationship of these viruses. Herpesvirus infections in reptiles are often characterised by non-pathognomonic signs including stomatitis, encephalitis, conjunctivitis, hepatitis and proliferative lesions. With the exception of fibropapillomatosis in marine turtles, the absence of specific clinical signs has fostered misdiagnosis and underreporting of the actual disease burden in reptilian populations and hampered potential investigations that could lead to the effective control of these diseases. In addition, complex life histories, sampling bias and poor monitoring systems have limited the assessment of the impact of herpesvirus infections in wild populations and captive collections. Here we review the current published knowledge of the taxonomy, pathogenesis, pathology and epidemiology of reptilian herpesviruses.

Development and validation of a quantitative PCR assay for detection of Terrapene herpesvirus 2 in eastern box turtles (Terrapene carolina carolina)

Herpesviruses are associated with disease in many chelonian species, resulting in pathology such as respiratory tract infection, stomatitis, conjunctivitis, hepatitis, and papillomatosis. Herpesvirus-associated fibropapillomas cause significant morbidity and mortality in marine turtles, and have been identified in an eastern box turtle (Terrapene carolina carolina) infected with Terrapene herpesvirus 2 (TerHV2). Further investigation is necessary to understand the impact of carcinogenic herpesviruses on chelonian health; however, reliable and specific methods for detection and quantitation of herpesviral load are lacking. The purpose of this study was to develop and validate a quantitative PCR assay for detection of TerHV2 in box turtles. TaqMan primer-probes were developed targeting the DNA polymerase gene. Inter- and intra-assay variability, linear range of detection, limit of detection, and specificity were assessed. The assay was highly specific for TerHV2, failing to amplify seven closely-related chelonian herpesviruses. It performed with high efficiency (slope = -3.52, R² = 1, efficiency = 92.29 %), low intra-assay variability and low inter-assay variability (coefficient of variation ≤ 1.25 % at all standard dilutions). Reaction efficiency was not impacted in the presence of box turtle DNA from combined oral/cloacal swabs or whole blood. This qPCR assay has a linear range of detection from 10⁷ to 10¹ viral copies per reaction and provides a valuable tool in the surveillance and characterization of TerHV2 in box turtles.