Detection of a novel herpesvirus associated with squamous cell carcinoma in a free-ranging Blanding's turtle

Development and analytical validation of a novel quantitative PCR assay for the detection of Trachemys herpesvirus 1

Emerging infectious diseases are a threat that contributes to the decline of global chelonian species. Herpesviruses are among the most impactful pathogens described in chelonians and are frequently associated with a range of presentations across hosts with the potential for severe morbidity and mortality. Trachemys herpesvirus 1 (TrHV1) has been reported in red-eared and yellow-bellied sliders (Trachemys scripta elegans and Trachemys scripta scripta, respectively) but is largely understudied. Invasive red-eared sliders may serve as a reservoir for transmission to sympatric native species. This study aimed to develop a sensitive and specific quantitative real-time PCR (qPCR) assay for the detection of TrHV1 DNA to aid in the characterization of the epidemiology of this virus in aquatic turtles. Two TaqMan-MGB FAM-dye labeled primer-probe sets were designed and evaluated using plasmid dilutions. The higher performing assay was specific for TrHV1 DNA and had a linear dynamic range of 1.0 × 107 to 1.0 × 101 copies per reaction with an R2 of 0.999, slope of -3.386, and efficiency of 97.39%. The limit of detection was 101 copies per reaction, and there was no loss of reaction efficiency in the presence of TrHV1-negative chelonian oral-cloacal DNA. Overall, the Trachemys herpesvirus 1 assay meets established criteria for acceptable qPCR assays and will be a valuable tool in characterizing the epidemiology of Trachemys herpesvirus 1 in chelonians.

Metastasizing squamous cell carcinoma in a 50-year-old Eastern Hermann's tortoise (Testudo hermannii boettgeri)

A 50-year-old female Hermann's tortoise (Testudo hermannii boettgeri) was presented with anorexia and lethargy. Clinical examination revealed multiple, visually inconspicuous but indentable areas in the shell corresponding to osteolysis radiographically. Soft tissue nodules and osteolytic lesions were also noted in the limbs. Laboratory results revealed elevated aspartate aminotransferase activity and uric acid concentrations, hypoglycemia, and hyperphosphatemia. Klebsiella oxytoca was isolated from a biopsied scutal area, and the biopsy suggested neoplasia. After a short period of clinical improvement, the animal's condition deteriorated, and it died. Post mortem computed tomography revealed polyostotic lytic lesions of multiple bones and the shell with associated soft tissue nodules protruding into the coelom, and nodular lung lesions. Necropsy, histopathology, and immunohistochemistry secured a diagnosis of a poorly differentiated, pan-cytokeratin-positive squamous cell carcinoma with widespread soft tissue and bone metastases, osteolysis and desmoplasia.

Development of subfamily-based consensus PCR assays for the detection of human and animal herpesviruses

Consensus PCR assays that can be used to sensitively detect several herpesvirus (HV) species across the different subfamilies were developed in this study. Primers containing degenerate bases were designed to amplify regions of the DNA polymerase (DPOL) gene of alpha- and gamma-HVs, and the glycoprotein B (gB) gene of beta-HVs in a singleplex, non-nested touchdown PCR format. The singleplex touchdown consensus PCR (STC-PCR) was used to amplify the DNA of eight human and 24 animal HVs. The assay was able to detect the lowest DNA dilution of 10^-5 for alpha-HVs and 10^-3 for beta- and gamma-HVs. In comparison, lowest detection limits of 10^-5, 10^-3, and 10^-2 were obtained for alpha-, beta-, and gamma-HVs respectively when a nested PCR was used. The findings in this study suggest that the STC-PCR assays can be employed for the molecular surveys and clinical detection of novel and known HVs.

EMYDID HERPESVIRUS 1 INFECTIONS IN WESTERN POND TURTLES (ACTINEMYS MARMORATA) AND A RED-EARED SLIDER (TRACHEMYS SCRIPTA ELEGANS) WITH FATAL AND NONFATAL OUTCOMES

Herpesviruses are important pathogens in zoologic chelonian collections and have been associated with fatal disease in turtles of the family Emydidae. In this report, three western pond turtles (Actinemys marmorata), living in a mixed-species freshwater turtle exhibit, presented with varying degrees of lethargy, pallor, generalized edema, and cloacal hemorrhage before death within a 2-wk period. Postmortem findings included necrohemorrhagic enterocolitis, necrotizing splenitis, hepatic necrosis, esophagitis, thymic necrosis, and pneumonia with epithelial necrosis and degeneration of the trachea and kidneys. Intraepithelial, intranuclear, amphophilic to eosinophilic, Cowdry type A viral inclusion bodies were identified in the intestinal tract, liver, spleen, kidney, trachea, lung, and thymus. PCR amplification and sequencing of liver tissue produced amplicons that were 100% homologous with emydid herpesvirus 1 (EmyHV-1). Molecular screening of cohoused emydid turtles revealed that a red-eared slider (Trachemys scripta elegans) and a western pond turtle, both asymptomatic, were PCR-positive for EmyHV-1 on combined oral-cloacal swabs. This report describes, for the first time, EmyHV-1-associated disease in western pond turtles and molecularly identifies EmyHV-1 in an asymptomatic red-eared slider.

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.