HEALTH ASSESSMENT OF FREE-RANGING CHELONIANS IN AN URBAN SECTION OF THE BRONX RIVER, NEW YORK, USA

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.

One Health Approach to Globalizing, Accelerating, and Focusing Amphibian and Reptile Disease Research-Reflections and Opinions from the First Global Amphibian and Reptile Disease Conference

The world's reptiles and amphibians are experiencing dramatic and ongoing losses in biodiversity, changes that can have substantial effects on ecosystems and human health. In 2022, the first Global Amphibian and Reptile Disease Conference was held, using One Health as a guiding principle. The conference showcased knowledge on numerous reptile and amphibian pathogens from several standpoints, including epidemiology, host immune defenses, wild population effects, and mitigation. The conference also provided field experts the opportunity to discuss and identify the most urgent herpetofaunal disease research directions necessary to address current and future threats to reptile and amphibian biodiversity.

A novel herpesvirus from a wild-caught Madagascar spider tortoise shows evidence of host-viral coevolution with a duplication event in Durocryptodira

Herpesviruses can be significant reptile pathogens. Herpesviral infection in a wild-caught, male spider tortoise (Pyxis arachnoides) under human care was detected during a routine wellness examination prior to transition between zoologic organizations. The tortoise had no clinical signs of illness. Oral swabs obtained during a physical examination as part of pre-shipment risk mitigation for infectious disease were submitted for consensus herpesvirus PCR assay and sequencing. Based on comparative sequence analysis, the novel herpesvirus identified is a member of the subfamily Alphaherpesvirinae. Studies of herpesviral phylogeny in chelonian species support branching patterns of turtle herpesviruses that closely mirror those of their hosts. The symmetry of these patterns is suggestive of close codivergence of turtle herpesviruses with their host species. The distribution of these viruses in both tortoises and emydids suggests a phylogenetic duplication event in the herpesviruses after host divergence of the Pleurodira and basal to the divergence of Americhelydia. Herpesviral infections have been documented to cause higher morbidity when introduced to aberrant host species, and significant consideration must be given to the presence of herpesviruses in the management of tortoise collections, particularly collections that include various species of testudines.

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.

Plasma complement activation mechanisms differ in ornate (Terrapene ornata ornata) and eastern box turtles (Terrapene carolina carolina)

Eastern (Terrapene carolina carolina) and ornate (Terrapene ornata ornata) box turtles have robust plasma antibacterial activity, however, the mechanism behind this activity is unknown. We used sheep red blood cell (SRBC) hemolysis assays, mannan-affinity chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) to explore the mechanisms of complement activity in box turtles. Plasma from both species demonstrated volume, time, and temperature-dependent SRBC hemolysis, with significantly greater hemolytic activity in ornate box turtle plasma. Hemolytic activity was highly attenuated following treatment with heat, EDTA, and salicylaldoxime in both species, but was unchanged after treatment with methylamine and ammonium hydroxide. Two abundant mannan-binding proteins (presumed C-type lectins) were identified in eastern box turtle plasma using SDS-PAGE and MALDI-TOF, but ornate box turtles did not express either protein. Eastern box turtles appear to rely on the lectin pathway of complement activation while ornate box turtles utilize the alternative pathway. This study provides further evidence that mechanisms underlying immune function are not always conserved between closely related species. This finding may have important implications for explaining species differences in susceptibility to emerging threats such as disease, toxicants, and climate change.

Emerging Infectious Diseases of Chelonians: An Update

Chelonians are increasingly challenged by anthropogenic threats and disease. This article summarizes recent literature and clinical experiences regarding 4 emerging infectious diseases in turtles and tortoises: ranaviruses, cryptosporidiosis, intranuclear coccodiosis of Testudines, and Emydomyces testavorans.

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.