Further evidence of Chelonid herpesvirus 5 (ChHV5) latency: high levels of ChHV5 DNA detected in clinically healthy marine turtles

Epidemiology of marine turtle fibropapillomatosis and tumour-associated chelonid alphaherpesvirus 5 (ChHV5; Scutavirus chelonidalpha5) in North-Western Mexico: a scoping review implementing the one health approach

Fibropapillomatosis (FP) - tumour-associated chelonid alphaherpesvirus 5 (ChHV5; Scutavirus chelonidalpha5) - is a disease that affect marine turtles around the world, and characterized by the formation of cutaneous tumours that can appear anywhere on the body. We carried out a thorough literature search (from 1990 to 2024) in the feeding sites of North-western Mexico, a region that hosts important habitats for feeding, development, and reproduction for five of the seven existing sea turtle species. We found 18 reports recording a total of 32 cases of FP and/or ChHV5/Scutavirus chelonidalpha5 in coastal and insular areas of North-western Mexico. Baja California Sur resulted with the highest number of cases (75%). While the first case of ChHV5/Scutavirus chelonidalpha5 infection was reported in 2004, the presence of FP tumours was reported in 2014 and became more frequent between 2019 and 2024. The affected species were black, Chelonia mydas (50%), olive ridley, Lepidochelys olivacea (46.8%) and loggerhead turtles, Caretta caretta (3.2%). Tumours occurred mainly in anterior flippers (46.1%) and neck (22.5%), and most had a nodular and verrucous appearance with a rough surface. In the study region, there is a potential sign of the emergence of the ChHV5/Scutavirus chelonidalpha5 infections and FP disease during the last 20 years, with a rapid increase during the last 10 years. As long as infections by ChHV5/Scutavirus chelonidalpha5 and the prevalence of the FP disease may be potentially influenced by anthropogenic activities, a One Health approach is needed to understand and improve sea turtles' health.

Fibropapillomatosis: A Review of the Disease with Attention to the Situation Northern Coast of Brazil

Fibropapillomatosis in sea turtles is a potentially debilitating and fatal disease for which there is still a lack of knowledge, especially for specific regions of Brazil. The diagnosis is made through the observation of clinical manifestations, and despite its association with Chelonid Alphaherpesvirus 5 (ChHV5) as the etiological agent, the expression of the disease may also be related to immunological and environmental factors caused by anthropic degradation of the environment. Thus, this review aims to elucidate what is known about this disease globally, and especially in various regions of Brazil, promoting a better understanding of its evolution, spatiotemporal prevalence, and relationship with human activities. Furthermore, the review explores the molecular biology of ChHV5, including its genomic structure, replication cycle, and mechanisms of pathogenesis. The role of environmental factors, such as temperature and pollution, in modulating ChHV5 infection and FP development is also discussed. Additionally, the review summarizes current diagnostic methods for detecting ChHV5 infection in sea turtles, highlighting the importance of early detection and monitoring for effective disease management and conservation efforts. Finally, the review outlines future research directions aimed at improving our understanding of ChHV5 and developing strategies for FP control and prevention in sea turtle populations.

Exploring the relationship between environmental drivers and the manifestation of fibropapillomatosis in green turtles (Chelonia mydas) in eastern Brazil

Fibropapillomatosis (FP) is a disease characterized by epithelial tumors that can impede life-sustaining activities of sea turtles, especially green turtles (Chelonia mydas). FP is caused by a herpesvirus, but environmental factors are also thought to play a role in triggering FP tumor growth. In this study, we evaluate the epidemiology of FP tumors in green turtles along the coast of Espírito Santo, Brazil, a region where juvenile green turtles are known to aggregate with high FP prevalence. A dataset comprising 2024 beach-cast green turtles recorded through daily beach surveys on 400 km of coastline from 2018 to 2021 (inclusive) was evaluated. FP tumors were recorded in 40.9% of the individuals in this dataset, and presence of FP tumors was predicted by individual variables (presence of marine leeches, stranding code, curved carapace length, body mass-size residual) and characteristics of the stranding site (distance to nearest metallurgical plant, mean sea surface salinity (SSS), annual range of sea surface temperature (SST)). Additionally, a second dataset comprising detailed information about the size and anatomical distribution of tumors in 271 green turtles with FP from the same region was evaluated. Hierarchical clustering analysis revealed these turtles could be classified in three groups according to the anatomical distribution of their tumors, and in turn the group to which each turtle was assigned could be predicted by the study period (2010-2014 vs. 2018-2022) and by characteristics of the stranding/capture site (green turtle stranding density, mean sea surface chlorophyll-a concentration, mean SSS, mean SST, annual range of SST). These results corroborate that individual and environmental factors play a significant role driving FP epidemiology. Furthermore, the results suggest that rather than behaving as a single entity, FP may be seen as a mosaic of distinct anatomical patterns that are not necessarily driven by the same environmental factors.

Increased Prevalence and New Evidence of Multi-Species Chelonid Herpesvirus 5 (ChHV5) Infection in the Sea Turtles of Mabul Island, Borneo

Fibropapillomatosis (FP) is a debilitating tumor disease affecting all species of sea turtles globally. The most probable etiological agent for FP is the chelonid herpesvirus 5 (ChHV5). A 2015-2016 field survey of the sea turtles at Mabul Island, Sabah, Malaysia, found three green turtles (Chelonia mydas) with FP tumors. However, the presence of ChHV5 was confirmed in 7.8% (9/115) green turtles and was absent (0/16) in the hawksbill (Eretmochelys imbricata) turtles, as determined through molecular approaches. Subsequent to this, we managed to conduct field sampling of sea turtles in November 2019, just prior to the pandemic lockdown. Here, we aim to determine the extent of ChHV5 infection, and whether the virus has spread to other species of sea turtles around Mabul Island after the first reports of ChHV5 and FP. A total of 69 tissue samples were obtained from green (63), hawksbill (5), and olive ridley (Lepidochelys olivacea) (1) turtles in November 2019. We observed only one green turtle that exhibited FP tumors. To determine the presence of ChHV5, viral DNA was isolated from all the tissue samples, and polymerase chain reaction (PCR) analysis targeting three highly conserved regions of the virus, i.e., the capsid protein gene, glycoprotein H gene, and glycoprotein B gene, was performed. Out of 63 green turtles, 27 were positive for the presence of the virus. The prevalence of ChHV5 in the green turtles showed an increase of 42.9% as compared to the previous sampling conducted in 2015-2016. Additionally, for the first time, three out of the five hawksbill turtles, and one olive ridley turtle, were also PCR-positive for the virus. In conclusion, this study reveals that there has been an increase in ChHV5 infection among turtles in Mabul Island over the last 3 years. ChHV5 should be considered a potential threat, and mitigation efforts should be taken to prevent the spread of infection among the endangered sea turtles of Mabul Island and surrounding islands within the Coral Triangle.

Preparation of recombinant glycoprotein B (gB) of Chelonid herpesvirus 5 (ChHV5) for antibody production and its application for infection detection in sea turtles

The Chelonid herpesvirus 5 (ChHV5) infection possibly associated to the fibropapillomatosis (FP) disease in sea turtles worldwide remains largely unknown and limited studies have used serological approaches to detection of antibodies against ChHV5 in sea turtles with or without FP. We aimed to develop diagnostic platforms based on the viral glycoprotein B (gB) for ChHV5 infection. In this study, five recombinant sub-fragments of the gB protein were successfully expressed and subsequently served as antigens for both seroprevalence and antibody production. The results indicated that the five expressed proteins harbored antigenicity, shown by the results of using sera from sea turtles that were PCR-positive for ChHV5. Moreover, seropositive sea turtles were significantly associated with FP (p < 0.05). We further used the expressed protein to produce antibodies for immunohistochemical analysis, and found that the in-house-generated sera specifically stained FP lesions while normal epithelium tissues remained negative. Of major importance, the reactivity in the ballooning degeneration area was much stronger than that in other regions of the FP lesion/tumour, thus indicating ChHV5 viral activities. In summary, the developed serological test and specific anti-gB antibodies for IHC analysis could be applied for further understanding of epidemiological distributions of ChHV5 infection in sea turtles, and studies of ChHV5 pathogenesis.

High Occurrence of Chelonid Alphaherpesvirus 5 (ChHV5) in Green Sea Turtles Chelonia mydas with and without Fibropapillomatosis in Feeding Areas of the São Paulo Coast, Brazil

Chelonid alphaherpesvirus 5 (ChHV5) has been consistently associated with fibropapillomatosis (FP), a neoplastic disease that affects sea turtles globally. The DNA of ChHV5 has been detected in cutaneous and noncutaneous tissues (e.g., lung) of green sea turtles Chelonia mydas with (FP+) and without (FP-) clinical signs of FP, indicating a persistent ChHV5 infection. Previously published and custom primer pairs were used to amplify the fragments of ChHV5 unique long (UL) partial genes (UL30 and UL18) through end-point PCR from cutaneous tumors (n = 31), nontumored skin (n = 49), and lungs (n = 26) from FP+ (n = 31) and FP- (n = 18) green sea turtles. The DNA of ChHV5 was detected in cutaneous tumors (80.6%, 25/31), nontumored skin (74.2%, 23/31 FP+; 27.8%, 5/18 FP-), and lung samples (91.7%, 11/12 FP+; 100%, 14/14 FP-). The high occurrence of ChHV5 observed in lung samples from FP- individuals was unexpected (14/14), providing the first evidence of ChHV5 DNA presence in lungs of individuals without FP. Our results also revealed high ChHV5 occurrence among the tested cohort (93.9%, 46/49) and suggested that a large proportion (83.4%, 15/18) of FP- green sea turtles had subclinical ChHV5 infections. Hence, our findings support the hypothesis that ChHV5 requires one or more possibly environmental or immune-related co-factors to induce FP.

First Evidence of Chelonid Herpesvirus 5 (ChHV5) Infection in Green Turtles (Chelonia mydas) from Sabah, Borneo

Fibropapillomatosis (FP) of sea turtles is characterised by cutaneous tumours and is associated with Chelonid herpesvirus 5 (ChHV5), an alphaherpesvirus from the family Herpesviridae. Here, we provide the first evidence of ChHV5-associated FP in endangered Green turtles (Chelonia mydas) from Sabah, which is located at the northern region of Malaysian Borneo. The aims of our study were firstly, to determine the presence of ChHV5 in both tumour exhibiting and tumour-free turtles using molecular techniques and secondly, to determine the phylogeography of ChHV5 in Sabah. We also aim to provide evidence of ChHV5 infection through histopathological examinations. A total of 115 Green turtles were sampled from Mabul Island, Sabah. We observed three Green turtles that exhibited FP tumours and were positive for ChHV5. In addition, six clinically healthy turtles (with no presence of tumours) were also positive for the virus based on Polymerase Chain Reaction of three viral genes (Capsid protein gene UL18, Glycoprotein H gene UL22, and Glycoprotein B gene UL27). The prevalence of the ChHV5 was 5.22% in asymptomatic Green turtles. Epidermal intranuclear inclusions were identified in tumour lesions upon histopathological examination. In addition, phylogenetic analyses of the UL18, UL22, UL27, and UL30 gene sequences showed a worldwide distribution of the ChHV5 strain with no clear distinction based on geographical location suggesting an interoceanic connection and movement of the sea turtles. Thus, the emergence of ChHV5 in Green turtles in the waters of Sabah could indicate a possible threat to sea turtle populations in the future and requires further monitoring of the populations along the Bornean coast.

EVALUATION OF IMMUNE FUNCTION IN TWO POPULATIONS OF GREEN SEA TURTLES (CHELONIA MYDAS) IN A DEGRADED VERSUS A NONDEGRADED HABITAT

There is a strong correlation between degraded marine habitats and the prevalence of diseases such as green turtle fibropapillomatosis (GTFP) in coastal populations. In GTFP, small to large tumors grow on the turtle's soft tissues and shell, while internal nodules may also occur. The disease primarily affects juvenile green sea turtles (Chelonia mydas) that reside in nearshore waters. As a link has been shown between environmental pollution and immune suppression in a variety of animals, the objective of our research was to compare innate and adaptive immune responsiveness in green sea turtles from a severely degraded and a more pristine habitat, which differ greatly in rates of GTFP. We quantified phagocytosis by flow cytometry and performed in vitro stimulation analysis to measure activity of both the innate and adaptive immune systems in wild-caught Florida green turtles. Sea turtles from the degraded environment, both with and without visible cutaneous tumors, exhibited significantly reduced phagocytosis and stimulation indices than did those from the less polluted environment. Our results suggest that environmental factors may contribute to the development of GTFP and thus can impact the health of sea turtle populations.

Gene expression changes with tumor disease and leech parasitism in the juvenile green sea turtle skin transcriptome

Emerging infectious diseases are a major threat to biodiversity in the 21st century. Fibropapillomatosis (FP) is an epithelial tumor disease that affects immature and adult marine turtles worldwide, particularly green turtles (Chelonia mydas). We know little about the host factors contributing to FP susceptibility, in part because transcriptomic studies that compare transcript expression in turtles with and without FP are lacking. Here, we performed RNA-Seq on healthy skin tissue from immature C. mydas in the Indian River Lagoon, Florida, USA, comparing turtles (1) with and without FP and (2) with and without leech parasites, a putative vector of FP. We assembled a de novo C. mydas skin transcriptome to identify transcripts with significant differential expression (DE) across FP and leech categories. Significant DE transcripts were found across FP and leech comparisons, including 10 of the same transcripts with DE across both comparisons. Leech-positive individuals significantly upregulated different immune and viral interaction transcripts than did leech-negative individuals, including viral interaction transcripts associated with herpesvirus interactions. This finding strengthens the role of marine leeches as mechanical vectors of Chelonid herpesvirus 5 (ChHV5) which has been implicated as a causative agent of FP. FP-positive turtles upregulated several tumor progression and suppression transcripts relative to FP-negative turtles, which had no significant DE tumor progression transcripts. FP-positive turtles also upregulated significantly more protein interaction transcripts than FP-negative turtles. DE transcripts across leech comparisons showed no functional enrichment, whereas DE transcripts across FP comparisons showed some GO terms were enriched in FP-positive and FP negative turtles. Notably, only FP-negative turtles were enriched for GO terms involved in acquired and inflammatory immune gene regulation. Overall, our DE transcripts included several candidate genes that may play important roles in C. mydas resistance to or recovery from FP, highlighting that transcriptomics provides a promising venue to understand this impactful disease. Continued investigation of C. mydas responses to FP and leech affliction is imperative for species persistence and the conservation of marine ecosystems worldwide due to the essential role of sea turtles in ecosystem function and stability.

Chelonid Alphaherpesvirus 5 Prevalence and First Confirmed Case of Sea Turtle Fibropapillomatosis in Grenada, West Indies

Chelonid alphaherpesvirus 5 (ChHV5) is strongly associated with fibropapillomatosis, a neoplastic disease of sea turtles that can result in debilitation and mortality. The objectives of this study were to examine green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) sea turtles in Grenada, West Indies, for fibropapillomatosis and to utilize ChHV5-specific PCR, degenerate herpesvirus PCR, and serology to non-invasively evaluate the prevalence of ChHV5 infection and exposure. One-hundred and sixty-seven turtles examined from 2017 to 2019 demonstrated no external fibropapilloma-like lesions and no amplification of ChHV5 DNA from whole blood or skin biopsies. An ELISA performed on serum detected ChHV5-specific IgY in 18/52 (34.6%) of green turtles tested. In 2020, an adult, female green turtle presented for necropsy from the inshore waters of Grenada with severe emaciation and cutaneous fibropapillomas. Multiple tumors tested positive for ChHV5 by qPCR, providing the first confirmed case of ChHV5-associated fibropapillomatosis in Grenada. These results indicate that active ChHV5 infection is rare, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time and further studies comparing host genetics and immunologic factors, as well as examination into extrinsic factors that may influence disease, are warranted.

Environmental DNA monitoring of oncogenic viral shedding and genomic profiling of sea turtle fibropapillomatosis reveals unusual viral dynamics

Pathogen-induced cancers account for 15% of human tumors and are a growing concern for endangered wildlife. Fibropapillomatosis is an expanding virally and environmentally co-induced sea turtle tumor epizootic. Chelonid herpesvirus 5 (ChHV5) is implicated as a causative virus, but its transmission method and specific role in oncogenesis and progression is unclear. We applied environmental (e)DNA-based viral monitoring to assess viral shedding as a direct means of transmission, and the relationship between tumor burden, surgical resection and ChHV5 shedding. To elucidate the abundance and transcriptional status of ChHV5 across early, established, regrowth and internal tumors we conducted genomics and transcriptomics. We determined that ChHV5 is shed into the water column, representing a likely transmission route, and revealed novel temporal shedding dynamics and tumor burden correlations. ChHV5 was more abundant in the water column than in marine leeches. We also revealed that ChHV5 is latent in fibropapillomatosis, including early stage, regrowth and internal tumors; higher viral transcription is not indicative of poor patient outcome, and high ChHV5 loads predominantly arise from latent virus. These results expand our knowledge of the cellular and shedding dynamics of ChHV5 and can provide insights into temporal transmission dynamics and viral oncogenesis not readily investigable in tumors of terrestrial species.

The Concurrent Detection of Chelonid Alphaherpesvirus 5 and Chelonia mydas Papillomavirus 1 in Tumoured and Non-Tumoured Green Turtles

Simple Summary

Characterised by benign tumours, fibropapillomatosis is a debilitating disease that predominantly afflicts the endangered green turtle (Chelonia mydas). A growing body of evidence has associated these tumours with a herpesvirus. However, a recent study detected both herpesvirus and papillomavirus in these tumours. This result challenged the idea that the herpesvirus is the sole virus associated with this disease. The present study aimed to better understand the co-occurrence of these viruses in turtles with fibropapillomatosis (in both tumour samples and non-tumoured skin samples), in addition to samples from non-tumoured turtles. Both viruses were detected in all sample types, with the 43.5% of tumours containing both herpesvirus and papillomavirus. Tumour samples were found to contain the most herpesvirus while the highest amount of papillomavirus was detected in non-tumoured skin from turtles with tumours. Collectively, these results pivot the way we think about this disease; as an infectious disease where two separate viruses may be at play.

Abstract

Characterised by benign tumours, fibropapillomatosis (FP) is a debilitating disease that predominantly afflicts the endangered green turtle (Chelonia mydas). A growing body of histological and molecular evidence has associated FP tumours with Chelonid alphaherpesvirus 5 (ChHV5). However, a recent study which detected both ChHV5 and Chelonia mydas papillomavirus 1 (CmPV1) DNA in FP tumour tissues has challenged this hypothesis. The present study aimed to establish a probe-based qPCR to assess the wider prevalence of CmPV1 and co-occurrence with ChHV5 in 275 marine turtles foraging in waters adjacent to the east coast of Queensland, Australia: three categories: Group A (FP tumours), Group B (non-tumoured skin from FP turtles) and Group C (non-tumoured skin from turtles without FP). Concurrent detection of ChHV5 and CmPV1 DNA is reported for all three categories, where Group A had the highest rate (43.5%). ChHV5 viral loads in Group A were significantly higher than loads seen in Group B and C. This was not the case for CmPV1 where the loads in Group B were highest, followed by Group A. However, the mean CmPV1 load for Group A samples was not significantly different to the mean load reported from Group B or C samples. Collectively, these results pivot the way we think about FP; as an infectious disease where two separate viruses may be at play.

Molecular Characterization of Chelonid Alphaherpesvirus 5 in a Black Turtle (Chelonia mydas) Fibropapilloma from Baja California Sur, Mexico

Simple Summary

Fibropapillomatosis in sea turtles is a neoplastic disease associated with an infection by chelonid alphaherpesvirus 5, which can be fatal to turtles. The Baja California peninsula in the Mexican Pacific has been a relatively pristine environment for local aquatic wildlife; however, in the last decade, several turtles with this disease have been reported in the foraging areas of the region. Reasons for this are unknown but may be related to population growth, the surge of unchecked tourism, pollution, and fisheries, which have increased in the area over the past two decades. Finding a black turtle with fibropapillomatosis and chelonid alphaherpesvirus 5 in a natural protected area to host one of the most important foraging areas for sea turtles in the Mexican Pacific represents a potential risk for the population of black turtles and other species of sea turtles that visit the feeding grounds of the peninsula. This suggests a need to strengthen research lines on the west coast of Mexico and generate conservation strategies for organisms and the ecosystems that they inhabit.

Abstract

During routine monitoring in Ojo de Liebre Lagoon, Mexico, a juvenile black turtle (Chelonia mydas) was captured, physically examined, measured, weighed, sampled, and tagged. The turtle showed no clinical signs suggestive of disease. Eleven months later, this turtle was recaptured in the same area, during which one lesion suggestive of fibropapilloma on the neck was identified and sampled for histopathology and molecular analysis. Histopathology revealed hyperkeratosis, epidermal hyperplasia, acanthosis, papillary differentiation and ballooning degeneration of epidermal cells, increased fibroblasts in the dermis, and angiogenesis, among other things. Hematological values were similar to those reported for clinically healthy black turtles and did not show notable changes between the first capture and the recapture; likewise, clinicopathological evaluation did not show structural or functional damage in the turtle’s systems. The chelonid alphaherpesvirus 5 (ChHV5) UL30 gene was amplified and sequenced for phylogeny; Bayesian reconstruction showed a high alignment with the genus Scutavirus of the Eastern Pacific group. This is one of the first reports of ChHV5 in a cutaneous fibropapilloma of a black turtle in the Baja California peninsula.

Molecular Assessment of Chelonid Alphaherpesvirus 5 Infection in Tumor-Free Green (Chelonia mydas) and Loggerhead (Caretta caretta) Sea Turtles in North Carolina, USA, 2015-2019

Simple Summary

Fibropapillomatosis is a debilitating tumor disease of sea turtles that is sometimes fatal. This disease is a key concern for sea turtle rehabilitation facilities due to its infectious nature, as it is associated with a virus called chelonid alphaherpesvirus 5. This is the first study to analyze antibodies to this virus in loggerhead sea turtles and represents the most complete dataset on viral detection in sea turtles encountered in the more northern latitudes of their habitat in the western Atlantic.

Abstract

Fibropapillomatosis is associated with chelonid alphaherpesvirus 5 (ChHV5) and tumor formation in sea turtles. We collected blood samples from 113 green (Chelonia mydas) and 112 loggerhead (Caretta caretta) turtles without fibropapillomatosis, including 46 free-ranging turtles (20 green turtles, 26 loggerheads), captured in Core Sound, North Carolina, and 179 turtles (93 green turtles, 86 loggerheads) in rehabilitative care in North Carolina. Blood samples were analyzed for ChHV5 DNA using quantitative polymerase chain reaction (qPCR), and for antibodies to ChHV5 peptides using an enzyme-linked immunosorbent assay (ELISA). None of the samples from foraging turtles tested positive for ChHV5 by qPCR; ELISA was not used for foraging turtles. Samples from 18/179 (10.1%) rehabilitating turtles tested positive for ChHV5 using qPCR, and 32/56 (57.1%) rehabilitating turtles tested positive for antibodies to ChHV5 using ELISA. Five turtles that tested positive by qPCR or ELISA at admission converted to being undetectable during rehabilitation, and five that initially tested negative converted to being positive. Both sea turtle species were significantly more likely to test positive for ChHV5 using ELISA than with qPCR (p < 0.001). There was no difference in the proportions of green turtles versus loggerheads that tested positive for ChHV5 using qPCR, but loggerheads were significantly more likely than green turtles to test positive for ChHV5 using ELISA. This finding suggests that loggerheads infected with ChHV5 at some point in their life may be more able than green turtles to mount an effective immune response against recrudescent infection, pointing to species-specific genetic differences in the two species’ immune response to ChHV5 infection. This is the first study to analyze antibodies to ChHV5 in loggerhead turtles and represents the most complete dataset on ChHV5 DNA detection in sea turtles encountered in the more northern latitudes of their western Atlantic habitat.

Atypical ocular Chelonoid herpesvirus manifestations in a captive Loggerhead turtle (Caretta caretta)

A captive loggerhead turtle (Caretta caretta) of unknown sex, 3 years of age, presented with bilateral mucoid secretions, severe chemosis, conjunctival hyperemia, and globe retraction. The animal was evaluated ophthalmologically and systemically, and hematological, microbiological, and conjunctival cytological and biopsy samples were collected for complementary diagnosis. The histopathological examination showed amphophilic intranuclear inclusions associated with severe inflammatory infiltrate. The diagnosis of Chelonid alphaherpesvirus 5 (ChAHV 5) was confirmed with end point PCR. Following systemic treatment with L-lysine, acyclovir and vitamin A, the ocular signs resolved. No amphophilic intranuclear inclusions were seen in a follow-up biopsy 5 months later, and there has been no recurrence of clinical ophthalmic signs during a 4-year follow-up. It is suggested that ChAHV 5 be considered as a differential diagnosis in captive marine turtles that present for conjunctival disease other than fibropapillomatosis.

Genetic Analysis of Chelonid Herpesvirus 5 in Marine Turtles from Baja California Peninsula

The Chelonid herpesvirus 5 (ChHV5) is the primary etiological agent associated with fibropapillomatosis (FP), a neoplastic disease in marine turtles. In this study, we report for the first time ChHV5 in marine turtles and a leech from Baja California Peninsula. Eighty-seven black, olive or loggerhead turtle species, one FP tumor and five leeches were analyzed. The tumor sample from an olive, a skin sample from a black and a leech resulted positive of ChHV5 for conventional PCR. Two viral variants were identified and grouped within the Eastern Pacific phylogenetic group, suggesting a possible flow of the virus in this region.

Differences in Antibody Responses against Chelonid Alphaherpesvirus 5 (ChHV5) Suggest Differences in Virus Biology in ChHV5-Seropositive Green Turtles from Hawaii and ChHV5-Seropositive Green Turtles from Florida

Fibropapillomatosis (FP) is a tumor disease associated with a herpesvirus (chelonid herpesvirus 5 [ChHV5]) that affects mainly green turtles globally. Understanding the epidemiology of FP has been hampered by a lack of robust serological assays to monitor exposure to ChHV5. This is due in part to an inability to efficiently culture the virus in vitro for neutralization assays. Here, we expressed two glycoproteins (FUS4 and FUS8) from ChHV5 using baculovirus. These proteins were immobilized on enzyme-linked immunosorbent assay plates in their native form and assayed for reactivity to two types of antibodies, full-length 7S IgY and 5.7S IgY, which has a truncated Fc region. Turtles from Florida were uniformly seropositive to ChHV5 regardless of tumor status. In contrast, in turtles from Hawaii, we detected strong antibody reactivity mainly in tumored animals, with a lower antibody response being seen in nontumored animals, including those from areas where FP is enzootic. Turtles from Hawaii actively shedding ChHV5 were more seropositive than nonshedders. In trying to account for differences in the serological responses to ChHV5 between green turtles from Hawaii and green turtles from Florida, we rejected the cross-reactivity of antibodies to other herpesviruses, differences in viral epitopes, or differences in procedure as likely explanations. Rather, behavioral or other differences between green turtles from Hawaii and green turtles from Florida might have led to the emergence of biologically different viral strains. While the strains from turtles in Florida apparently spread independently of tumors, the transmission of the Hawaiian subtype relies heavily on tumor formation.IMPORTANCE Fibropapillomatosis (FP) is a tumor disease associated with chelonid herpesvirus 5 (ChHV5) that is an important cause of mortality in threatened green turtles globally. FP is expanding in Florida and the Caribbean but declining in Hawaii. We show that Hawaiian turtles mount antibodies to ChHV5 mainly in response to tumors, which are the only sites of viral replication, whereas tumored and nontumored Floridian turtles are uniformly seropositive. Tumor viruses that depend on tumors for replication and spread are rare, with the only example being the retrovirus causing walleye dermal sarcoma in fish. The Hawaiian strain of ChHV5 may be the first DNA virus with such an unusual life history. Our findings, along with the fundamental differences in the life histories between Floridian turtles and Hawaiian turtles, may partly explain the differential dynamics of FP between the two regions.

Fibropapillomatosis prevalence and distribution in green turtles Chelonia mydas in Texas (USA)

Fibropapillomatosis (FP) is a neoplastic disease that can result in debilitating tumors in sea turtles. Initially identified in Florida, USA in 1937, it has since been detected in green turtle Chelonia mydas populations globally. FP was first identified and confirmed in Texas, USA in 2010. No FP tumors were documented in Texas prior to that year, though many green turtles were encountered and examined using standardized procedures since 1980. The present study was undertaken to identify temporal and spatial trends of FP prevalence in Texas since 2010. From 2010 through 2018, 1919 stranded or incidentally captured green turtles were documented with FP in Texas. FP prevalence was significantly correlated with year, hypothermic stunning, geographic region, and turtle size, as determined by logistic regression. FP was documented in <4.0% of the green turtles examined in Texas from 2010 to 2015, increasing to 21.6% in 2016, 27.3% in 2017, and 35.2% in 2018. More than twice as many hypothermic stunned green sea turtles had FP tumors as compared to those that were not hypothermic stunned. In Texas, FP was most prevalent in south Texas, particularly in the Laguna Madre, and associated channels. FP was more prevalent in turtles with straight carapace lengths 40.0-69.9 cm. The impact of this disease on green turtle population recovery in Texas is not yet apparent.

Presence of chelonid herpesvirus 5 (ChHV5) in sea turtles in northern Sinaloa, Mexico

The presence of fibropapilloma and its associated chelonid herpesvirus 5 (ChHV5) was assessed in 82 wild sea turtles. Olive ridley turtles Lepidochelys olivacea (n = 58) were caught in the pelagic Area of Marine Influence (AMI) (off the coast of Guasave, Sinaloa), and black turtles Chelonia mydas agassizii (n = 24) were captured in the Navachiste Lagoon System. The apparent physical condition was evaluated as 'good' or 'poor' by physical examination. The population structure and general health status was determined by condition index, hematocrit and total plasma protein. Detection of ChHV5 from skin samples was done by PCR. The overall physical condition of black turtles was good and all the individuals were tumor-free. Likewise, the physical condition of most olive ridley turtles was good, except for 10 individuals with poor condition. Of these, 4 had fibropapilloma-like tumors. PCR analyses showed that 3 tumors were ChHV5-positive. The DNA sequence showed 96% identity with ChHV5. All other skin samples from black or olive ridley turtles were ChHV5-negative. This is the first report of fibropapillomatosis-ChHV5 in foraging grounds off northern Sinaloa. The virus was present in a small proportion of L. olivacea individuals, a free-ranging species. It is suggested that infected turtles acquired the virus at a different location somewhere during their development before arriving in the AMI zone. This finding makes the case for setting up a health monitoring program for turtle populations in the area, enforcing sanitary measures to reduce the spread of the pathogen.

Molecular evolution of fibropapilloma-associated herpesviruses infecting juvenile green and loggerhead sea turtles

Chelonid Alphaherpesvirus 5 (ChHV5) has long been associated with fibropapillomatosis (FP) tumor disease in marine turtles. Presenting primarily in juvenile animals, FP results in fibromas of the skin, connective tissue, and internal organs, which may indirectly affect fitness by obstructing normal turtle processes. ChHV5 is near-universally present in tumorous tissues taken from affected animals, often at very high concentrations. However, there is also considerable asymptomatic carriage amongst healthy marine turtles, suggesting that asymptomatic hosts play an important role in disease ecology. Currently, there is a paucity of studies investigating variation in viral genetics between diseased and asymptomatic hosts, which could potentially explain why only some ChHV5 infections lead to tumor formation. Here, we generated a database containing DNA from over 400 tissue samples taken from green and loggerhead marine turtles, including multiple tissue types, a twenty year time span, and both diseased and asymptomatic animals. We used two molecular detection techniques, quantitative (q)PCR and nested PCR, to characterize the presence and genetic lineage of ChHV5 in each sample. We found that nested PCR across multiple loci out-performed qPCR and is a more powerful technique for determining infection status. Phylogenetic reconstruction of three viral loci from all ChHV5-positive samples indicated widespread panmixia of viral lineages, with samples taken across decades, species, disease states, and tissues all falling within the same evolutionary lineages. Haplotype networks produced similar results in that viral haplotypes were shared across species, tissue types and disease states with no evidence that viral lineages associated significantly with disease dynamics. Additionally, tests of selection on viral gene trees indicated signals of selection dividing major clades, though this selection did not divide sample categories. Based on these data, neither the presence of ChHV5 infection nor neutral genetic divergence between viral lineages infecting a juvenile marine turtle is sufficient to explain the development of FP within an individual.

Sea turtle fibropapilloma tumors share genomic drivers and therapeutic vulnerabilities with human cancers

Wildlife populations are under intense anthropogenic pressures, with the geographic range of many species shrinking, dramatic reductions in population numbers and undisturbed habitats, and biodiversity loss. It is postulated that we are in the midst of a sixth (Anthropocene) mass extinction event, the first to be induced by human activity. Further, threatening vulnerable species is the increased rate of emerging diseases, another consequence of anthropogenic activities. Innovative approaches are required to help maintain healthy populations until the chronic underlying causes of these issues can be addressed. Fibropapillomatosis in sea turtles is one such wildlife disease. Here, we applied precision-medicine-based approaches to profile fibropapillomatosis tumors to better understand their biology, identify novel therapeutics, and gain insights into viral and environmental triggers for fibropapillomatosis. We show that fibropapillomatosis tumors share genetic vulnerabilities with human cancer types, revealing that they are amenable to treatment with human anti-cancer therapeutics.

David Duffy et al. use a precision-medicine-based approach to study fibropapillomatosis tumors in sea turtles to identify environmental triggers and potential therapeutics. They show that these tumors share genetic similarities with human cancer types, and may be treatable using human anti-cancer therapies.

Development and validation of a quantitative PCR assay for detection of Emydoidea herpesvirus 1 in free-ranging Blanding's turtles (Emydoidea blandingii)

Blanding's turtles (Emydoidea blandingii), an endangered species in Illinois, have experienced range-wide declines because of habitat degradation and fragmentation, predation, and road mortality. While ongoing studies are crucial to a thorough understanding of the natural history and demographics in these disjointed Illinois populations, infectious disease threats have been largely unevaluated. Herpesvirus outbreaks have been associated with high morbidity and mortality in populations of captive tortoises and turtles worldwide, including the family Emydidae (pond and box turtles). However, novel herpesviruses including Terrapene herpesvirus 1, Emydid herpesvirus 1 and 2, and Glyptemys herpesvirus 1 and 2, have recently been identified in apparently healthy free-ranging freshwater turtles. In 2015, 20 free-ranging Blanding's turtles in DuPage County, Illinois were screened for a herpesvirus using consensus PCR. A novel herpesvirus species (Emydoidea herpesvirus 1; EBHV1) was identified in two animals and shared a high degree of sequence homology to other freshwater turtle herpesviruses. Two quantitative real-time PCR assays, using EBHV1 primer-1 and primer-2, were developed to target an EBHV1-specific segment of the DNA-dependent DNA polymerase gene and validated. Both assays performed with high efficiency (slope = -3.2; R² = 1), low intra-assay variability, and low inter-assay variability (coefficient of variation <2% at all dilutions). However, EBHV1 primer-2 displayed less variation and was selected to test clinical samples and five closely related herpesvirus control samples. Results indicate that this assay is specific for EBHV1, has a linear range of detection from 10⁸ to 10¹ viral copies per reaction, and can categorically detect as few as 1 viral copy per reaction. This qPCR assay provides a valuable diagnostic tool for future characterization of EBHV1 epidemiology.

Examining the Role of Transmission of Chelonid Alphaherpesvirus 5

Marine turtle fibropapillomatosis (FP) is a devastating neoplastic disease characterized by single or multiple cutaneous and visceral fibrovascular tumors. Chelonid alphaherpesvirus 5 (ChHV5) has been identified as the most likely etiologic agent. From 2010 to 2013, the presence of ChHV5 DNA was determined in apparently normal skin, tumors and swab samples (ocular, nasal and cloacal) collected from 114 olive ridley (Lepidochelys olivacea) and 101 green (Chelonia mydas) turtles, with and without FP tumors, on the Pacific coasts of Costa Rica and Nicaragua. For nesting olive ridley turtles from Costa Rica without FP, 13.5% were found to be positive for ChHV5 DNA in at least one sample, while in Nicaragua, all olive ridley turtles had FP tumors, and 77.5% tested positive for ChHV5 DNA. For green turtles without FP, 19.8% were found to be positive for ChHV5 DNA in at least one of the samples. In turtles without FP tumors, ChHV5 DNA was detected more readily in skin biopsies than swabs. Juvenile green turtles caught at the foraging site had a higher prevalence of ChHV5 DNA than adults. The presence of ChHV5 DNA in swabs suggests a possible route of viral transmission through viral secretion and excretion via corporal fluids.