DISSEMINATED OPHIDIOMYCES OPHIODIICOLA INFECTION IN A CAPTIVE EASTERN MASSASAUGA ( SISTRURUS CATENATUS CATENATUS )

CONTROLLED CLINICAL TRIAL USING TERBINAFINE NEBULIZATION TO TREAT WILD LAKE ERIE WATERSNAKES (NERODIA SIPEDON INSULARUM) WITH OPHIDIOMYCOSIS

Ophidiomycosis (snake fungal disease) is an important infectious disease caused by the fungus Ophidiomyces ophidiicola. To mitigate the disease's impact on individual snakes, a controlled clinical trial was conducted using terbinafine nebulization to treat snakes with ophidiomycosis. Fifty-three wild-caught Lake Erie watersnakes (Nerodia sipedon insularum) with apparent ophidiomycosis (skin lesions present, qPCR positive for O. ophidiicola) were divided into treatment and control groups: treatment snakes were nebulized with a 2 mg/ml terbinafine solution for 30 min daily for 30 d; control snakes received nebulization with 0.9% saline or no nebulization. Weekly physical exams were conducted to assign disease severity scores based on the number, type, location, and size of lesions, and qPCR was repeated after each 30-d course of treatment. Persistently qPCR-positive snakes received multiple nebulization courses. Terbinafine nebulization showed mixed results as a treatment for ophidiomycosis: 29.2% of animals treated with terbinafine showed molecular resolution of external disease, based on antemortem swabbing, following 3-6 mon of daily nebulization; this was significantly more than with saline nebulization (5%), but molecular resolution also occurred in 11.1% of snakes that received no treatment. Terbinafine nebulization did not significantly decrease clinical disease, as measured by disease severity scores. Evaluating molecular response to treatment using fungal quantities, terbinafine nebulization significantly reduced fungal quantity after three or more courses of treatment. These results indicate that, although terbinafine nebulization is a promising treatment for ophidiomycosis, snakes may require multiple nebulization courses and disease may not always resolve completely, despite treatment. This treatment may be most useful in snakes from managed populations that can be treated for several months, rather than wild snakes who are not releasable after multiple months in captivity.

Development and application of a qPCR-based genotyping assay for Ophidiomyces ophidiicola to investigate the epidemiology of ophidiomycosis

Ophidiomycosis (snake fungal disease) is an infectious disease caused by the fungus Ophidiomyces ophidiicola to which all snake species appear to be susceptible. Significant variation has been observed in clinical presentation, progression of disease, and response to treatment, which may be due to genetic variation in the causative agent. Recent phylogenetic analysis based on whole-genome sequencing identified that O. ophidiicola strains from the United States formed a clade distinct from European strains, and that multiple clonal lineages of the clade are present in the United States. The purpose of this study was to design a qPCR-based genotyping assay for O. ophidiicola, then apply that assay to swab-extracted DNA samples to investigate whether the multiple O. ophidiicola clades and clonal lineages in the United States have specific geographic, taxonomic, or temporal predilections. To this end, six full genome sequences of O. ophidiicola representing different clades and clonal lineages were aligned to identify genomic areas shared between subsets of the isolates. Eleven hydrolysis-based Taqman primer-probe sets were designed to amplify selected gene segments and produce unique amplification patterns for each isolate, each with a limit of detection of 10 or fewer copies of the target sequence and an amplification efficiency of 90-110%. The qPCR-based approach was validated using samples from strains known to belong to specific clades and applied to swab-extracted O. ophidiicola DNA samples from multiple snake species, states, and years. When compared to full-genome sequencing, the qPCR-based genotyping assay assigned 75% of samples to the same major clade (Cohen's kappa = 0.360, 95% Confidence Interval = 0.154-0.567) with 67-77% sensitivity and 88-100% specificity, depending on clade/clonal lineage. Swab-extracted O. ophidiicola DNA samples from across the United States were assigned to six different clonal lineages, including four of the six established lineages and two newly defined groups, which likely represent recombinant strains of O. ophidiicola. Using multinomial logistic regression modeling to predict clade based on snake taxonomic group, state of origin, and year of collection, state was the most significant predictor of clonal lineage. Furthermore, clonal lineage was not associated with disease severity in the most intensely sampled species, the Lake Erie watersnake (Nerodia sipedon insularum). Overall, this assay represents a rapid, cost-effective genotyping method for O. ophidiicola that can be used to better understand the epidemiology of ophidiomycosis.

Ophidiomyces ophidiicola detection and infection: a global review on a potential threat to the world’s snake populations

Ophidiomyces ophidiicola (Oo) is one of the most relevant fungal pathogens for snakes. It is the etiological agent of ophidiomycosis, an emerging disease causing dysecdysis, skin abnormalities, crusting cutaneous lesions, and ulcerations. Despite this major tegumentary “tropism”, Oo infection can be systemic and it is capable of inducing visceral lesions. Moreover, ophidiomycosis may lead to abnormalities of reproductive physiology, hunting behavior, and thermoregulation, thus increasing the risks of sublethal effects and predation on affected snakes. Oo seems horizontally transmitted and can induce postnatal mortality. This article reviews published data on Oo detection and infection in all snake species in countries around the world and categorizes these data using new classification parameters. The presence of this fungus has been recorded in 11 states (considering the USA as a whole); however, in four states, the mycosis has only been reported in snakes held in captivity. Detection and/or infection of Oo has been ascertained in 62 snake species, divided into nine families. The taxa have been categorized with diagnostic criteria in order to report, for each species, the highest rank of categorization resulting from all cases. Therefore, 20 species have been included within the class “Ophidiomycosis and Oo shedder”, 11 within “Ophidiomycosis”, 16 in “Apparent ophidiomycosis”, and 15 within “Ophidiomyces ophidiicola present”. We also discuss the significance and limits of case classifications and Oo’s impact on wild populations, and we suggest methods for preliminary surveillance. Standardized methods, interdisciplinary studies, and cooperation between various research institutions may facilitate further Oo screening studies, elucidate the unclear aspects of the disease, and protect ophidiofauna from this emerging threat at the global level.

INNATE IMMUNE FUNCTION IN LAKE ERIE WATERSNAKES (NERODIA SIPEDON INSULARUM) WITH OPHIDIOMYCOSIS

Ophidiomycosis, caused by the fungus Ophidiomyces ophidiicola, poses a threat to the health of wild and managed snakes worldwide. Variation in snake innate immunity, the primary defense against infection in reptiles, may explain the observed variation in ophidiomycosis clinical disease severity among snakes. In this study, two components of the innate immune response were examined in snake plasma. We investigated whether complement activity, as measured by sheep red blood cell hemolysis, and chitotriosidase activity were associated with ophidiomycosis disease severity and time in captivity in Lake Erie watersnakes (Nerodia sipedon insularum). There was no difference in complement-mediated hemolysis or chitotriosidase activities between snakes with varying levels of ophidiomycosis clinical severity sampled in the field. However, among snakes with skin lesions kept in captivity, chitotriosidase activity was significantly higher in snakes with mild disease, compared with snakes with severe disease, and hemolysis activity increased with time in captivity. Overall, Lake Erie watersnakes had higher complement activity, but lower chitotriosidase activity, compared with other reptile species. To our knowledge, this study is the first to describe chitotriosidase activity in a snake species. These results provide mixed evidence of associations between innate immune function and ophidiomycosis severity, and more work is needed to investigate differences among snake species.

RETROSPECTIVE REVIEW OF OPHIDIOMYCOSIS (OPHIDIOMYCES OPHIODIICOLA) AT THE SMITHSONIAN'S NATIONAL ZOOLOGICAL PARK (1983-2017)

A retrospective review of systemic or localized mycotic infections in captive snakes confirmed via biopsy or necropsy from 1983 to 2017 was performed at the Smithsonian's National Zoological Park. Quantitative polymerase chain reaction (qPCR) confirmed infection with Ophidiomyces ophiodiicola (Oo) in 36.8% (n = 14) of the 38 mycotic infections. Infections with Oo were evenly distributed over the 35-y period and lacked a sex predilection. There was a period prevalence of 4.5% of completed snake necropsy or biopsy cases that were Oo positive. Species affected included green anaconda (Eunectes murinus, n = 4), garden tree boa (Corallus hortulanus, n = 1), false water cobra (Hydrodynastes gigas, n = 5), yellow anaconda (Eunectes notaeus, n = 1), eastern milksnake (Lampropeltis triangulum, n = 1), Brazilian rainbow boa (Epicrates cenchria cenchria, n = 1), and eastern diamondback rattlesnake (Crotalus adamanteus, n = 1). Histopathology demonstrated one or more of the following: heterophilic to necrotizing epidermitis with or without granulomatous dermatitis (n = 12), granulomatous pneumonia (n = 5), granulomatous endophthalmitis (n = 1), and subcutaneous-intramuscular fungal granuloma (n = 1). This study documents the presence of ophidiomycosis in a captive collection for almost 40 years, despite current literature designating it a recently emerging pathogen.

Shell Lesions Associated With Emydomyces testavorans Infection in Freshwater Aquatic Turtles

A newly described onygenalean fungus, Emydomyces testavorans, has been isolated from ulcerative shell and skin lesions of freshwater aquatic chelonians. To investigate the shell lesions associated with infection and determine if any lesional features were unique to E. testavorans, tissues from turtles housed in zoological institutions (n = 45) in the United States and free-living turtles (n = 5) submitted for diagnostic biopsy or necropsy were examined. Free-living turtles were from geographically distinct habitats in Florida (n = 1) and Washington (n = 4) at the time of sampling. Histologic shell sections were evaluated for the presence or absence of specific lesional features. Infection with E. testavorans was evaluated in all cases by screening GMS (Grocott-Gomori's methenamine silver)-stained histologic sections for the presence of morphologically consistent fungi and by quantitative PCR (polymerase chain reaction) on representative frozen tissue or formalin-fixed paraffin-embedded sections. Additionally, culture was performed for 15 cases with available fresh/frozen tissue. In total, there were 17 PCR-confirmed E. testavorans cases, 29 cases with morphologically consistent fungi on GMS-stained sections, and 21 cases of shell lesions without histologic or molecular evidence of E. testavorans infection. Epithelial inclusion cysts, defined as cystic structures within the dermis lined by keratinized stratified squamous epithelium and containing necrotic bone and keratin debris, were significantly (P < .01) associated with E. testavorans infection. Other significantly associated shell lesions included squamous metaplasia, hyperkeratosis, inflammation, and osteonecrosis (P < .05). This study identified characteristic shell lesions associated with E. testavorans infection. Further studies to prove causality are needed.

Ophidiomycosis, an emerging fungal disease of snakes: Targeted surveillance on military lands and detection in the western US and Puerto Rico

Wildlife disease surveillance and pathogen detection are fundamental for conservation, population sustainability, and public health. Detection of pathogens in snakes is often overlooked despite their essential roles as both predators and prey within their communities. Ophidiomycosis (formerly referred to as Snake Fungal Disease, SFD), an emergent disease on the North American landscape caused by the fungus Ophidiomyces ophiodiicola, poses a threat to snake population health and stability. We tested 657 individual snakes representing 58 species in 31 states from 56 military bases in the continental US and Puerto Rico for O. ophiodiicola. Ophidiomyces ophiodiicola DNA was detected in samples from 113 snakes for a prevalence of 17.2% (95% CI: 14.4–20.3%), representing 25 species from 19 states/territories, including the first reports of the pathogen in snakes in Idaho, Oklahoma, and Puerto Rico. Most animals were ophidiomycosis negative (n = 462), with Ophidiomyces detected by qPCR (n = 64), possible ophidiomycosis (n = 82), and apparent ophidiomycosis (n = 49) occurring less frequently. Adults had 2.38 times greater odds than juveniles of being diagnosed with ophidiomycosis. Snakes from Georgia, Massachusetts, Pennsylvania, and Virginia all had greater odds of ophidiomycosis diagnosis, while snakes from Idaho were less likely to be diagnosed with ophidiomycosis. The results of this survey indicate that this pathogen is endemic in the eastern US and identified new sites that could represent emergence or improved detection of endemic sites. The direct mortality of snakes with ophidiomycosis is unknown from this study, but the presence of numerous individuals with clinical disease warrants further investigation and possible conservation action.

Selected Emerging Infectious Diseases of Squamata: An Update

This article details emerging infectious diseases that have devastating impacts on captive and wild squamates. Treatment advances have been attempted for Cryptosporidium infections in squamates. Gram-positive bacteria, Devriesea agamarum and Austwickia chelonae, are contributing to severe disease in captive and now in wild reptiles, some critically endangered. Nannizziposis, Paranannizziopsis, and Ophidiomyces continue to cause fatal disease as primary pathogens in wild and captive populations of squamates and sphenodontids. Nidovirus, bornavirus, paramyxovirus, sunshine virus, and arenavirus have emerged to be significant causes of neurorespiratory disease in snakes. Controlled studies evaluating environmental stability, disinfection, transmission control, and treatment are lacking.

Ophidiomycosis in Red Cornsnakes (Pantherophis guttatus): Potential Roles of Brumation and Temperature on Pathogenesis and Transmission

Ophidiomycosis (snake fungal disease) is caused by the fungus Ophidiomyces ophiodiicola. As ophidiomycosis is difficult to study in free-ranging snakes, a reliable experimental model is needed to investigate transmission, pathogenesis, morbidity, and mortality, and the effects of brumation and temperature on disease development. Our objective was to develop such a model via subcutaneous injection of O. ophiodiicola conidia in red cornsnakes (Pantherophis guttatus). The model was used to evaluate transmission and the effects of brumation and temperature in co-housed inoculated and noninoculated snakes. All 23 inoculated snakes developed lesions consistent with ophidiomycosis, including heterophilic and granulomatous dermatitis, cellulitis, and myositis, and embolic fungal granulomas throughout the liver and the coelomic connective tissue in 21/23 (91%). In the inoculated snakes, 21% of skin swabs, 37% of exuvia, and all liver samples tested positive by qPCR (quantitative polymerase chain reaction) for O. ophiodiicola. A post brumation skin swab from 1/12 noninoculated snakes that brumated in contact with inoculated snakes tested positive by qPCR, suggesting possible contact transmission. That snake had microscopic skin lesions consistent with ophidiomycosis, but no visible fungal elements. Of the 23 inoculated snakes, 20 (87%) died over the 70-day experiment, with ophidiomycosis considered the primary cause of death; 12 (52%) of the inoculated snakes died during brumation. Overall, this experimental model of ophidiomycosis reproduced skin lesions analogous to those of many natural cases, and internal lesions similar to the most severe natural cases. The study provides tentative experimental evidence for horizontal transmission in brumation, and offers a tool for future studies of this widespread snake disease.

Emydomyces testavorans, a New Genus and Species of Onygenalean Fungus Isolated from Shell Lesions of Freshwater Aquatic Turtles

The fungal order Onygenales includes many pathogens of humans and animals, and recent studies have shown some onygenalean fungi to be significant emerging pathogens of reptiles. Although many of these fungi have similar morphological features in histologic tissue sections, recent molecular analyses have revealed a genetically complex and diverse group of reptile pathogens comprising several genera, most notably Nannizziopsis, Ophidiomyces, and Paranannizziopsis Infections by members of these genera have been previously reported in a variety of reptile species, including crocodilians, lizards, snakes, and tuataras, with negative impacts on conservation efforts for some reptiles. Despite the well-documented pathogenicity of these fungi in all other extant reptile lineages, infection has not yet been reported in aquatic turtles. In this study, we report the isolation of an onygenalean fungus associated with shell lesions in freshwater aquatic turtles. The morphologic and genetic characteristics of multiple isolates (n = 21) are described and illustrated. Based on these features and results of a multigene phylogenetic analysis, a new genus and species, Emydomyces testavorans, are proposed for these fungi isolated from turtle shell lesions.