Development and use of a real-time polymerase chain reaction assay for the detection of Ophidiomyces ophiodiicola in snakes

Genetic mechanisms and biological processes underlying host response to ophidiomycosis (snake fungal disease) inferred from tissue-specific transcriptome analyses

Emerging infectious diseases in wildlife species caused by pathogenic fungi are of growing concern, yet crucial knowledge gaps remain for diseases with potentially large impacts. For example, there is detailed knowledge about host pathology and mechanisms underlying response for chytridiomycosis in amphibians and white-nose syndrome in bats, but such information is lacking for other more recently described fungal infections. One such disease is ophidiomycosis, caused by the fungus Ophidiomyces ophidiicola, which has been identified in many species of snakes, yet the biological mechanisms and molecular changes occurring during infection are unknown. To gain this information, we performed a controlled experimental infection in captive Prairie rattlesnakes (Crotalus viridis) with O. ophidiicola at two different temperatures: 20 and 26°C. We then compared liver, kidney, and skin transcriptomes to assess tissue-specific genetic responses to O. ophidiicola infection. Given previous histopathological studies and the fact that snakes are ectotherms, we expected highest fungal activity on skin and a significant impact of temperature on host response. Although we found fungal activity to be localized on skin, most of the differential gene expression occurred in internal tissues. Infected snakes at the lower temperature had the highest host mortality whereas two-thirds of the infected snakes at the higher temperature survived. Our results suggest that ophidiomycosis is likely a systemic disease with long-term effects on host response. Our analysis also identified candidate protein coding genes that are potentially involved in host response, providing genetic tools for studies of host response to ophidiomycosis in natural populations.

COMPARING THE EFFECTS OF LITHIUM HEPARIN AND DIPOTASSIUM ETHYLENEDIAMINETETRAACETIC ACID ON HEMATOLOGIC VALUES IN PRAIRIE RATTLESNAKES (CROTALUS VIRIDIS) AND LAKE ERIE WATER SNAKES (NERODIA SIPEDON INSULARUM)

Anticoagulants prevent clotting of blood samples and preserve cellular morphology for hematologic evaluations, but studies comparing anticoagulants are limited in snakes. The objective of this study was to evaluate the effects of lithium heparin (LH) and dipotassium ethylenediaminetetraacetic acid (EDTA) on hematologic values in prairie rattlesnakes (PR; Crotalus viridis, n = 16) and Lake Erie water snakes (LEWS; Nerodia sipedon insularum, n = 21). Venipuncture was performed and blood samples were immediately aliquoted into LH and EDTA microtainers. Packed cell volume (PCV), total solids (TS), 100-cell differential counts, and Avian Leukopet white blood cell counts (WBC) were determined for each anticoagulant. Passing-Bablok regression and Bland-Altman plots revealed that anticoagulant choice did not constantly or proportionally bias the values of any WBC parameter. Mixed models demonstrated that blood anticoagulated with EDTA had higher PCV in PR (P = 0.04) and TS in both species (P < 0.05). However, the magnitude of the differences attributable to anticoagulant choice was relatively small and likely not clinically important. Hemolysis was not appreciated in any samples. Our findings demonstrate that LH and EDTA are equally appropriate for use in PR and LEWS, but may require separate reference values.

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.

Factors Predicting Apparent Ophidiomycosis in Wild Brown Watersnakes (Nerodia taxispilota)

Ophidiomycosis, also known as snake fungal disease, is caused by Ophidiomyces ophidiicola and is a threat to snake conservation worldwide. Ophidiomycosis has been reported throughout much of the eastern US, and outbreaks have been associated with local population declines of already strained populations. Previous studies report significant variability in ophidiomycosis among species sampled, with higher prevalence typically observed in Nerodia spp. Although ophidiomycosis can lead to morbidity and mortality in affected individuals, little is known about disease dynamics in free-ranging populations. Herein, we examine how individual-specific factors (e.g., life stage [immature, mature], contaminant status, sex, hemograms) may be associated with ophidiomycosis status in the brown watersnake (Nerodia taxispilota). During 2018-19, we sampled 97 N. taxispilota from five locations along the Savannah River in South Carolina and Georgia, US. Ophidiomyces ophidiicola DNA was detected in 66 snakes for a prevalence of 68% (95% confidence interval, 59-77). Mature snakes had a significantly higher risk of apparent ophidiomycosis (skin lesions present and quantitative PCR [qPCR], positive) relative to immature snakes. Snakes classified as having possible (skin lesions present, but qPCR negative) or apparent ophidiomycosis exhibited a relative azurophilia and heterophilia compared with individuals classified as negative (P≤0.037). Nerodia taxispilota in this region appear to have a high prevalence of apparent ophidiomycosis (22%; 95% CI, 14-31), similar to previous reports from the southeastern US. Additional epidemiologic investigations are warranted to further elucidate other individual-specific and environmental factors that may dictate disease risk and outcomes in affected populations.

Paranannizziopsis spp. infections in wild snakes and a qPCR assay for detection of the fungus

The emergence of ophidiomycosis (or snake fungal disease) in snakes has prompted increased awareness of the potential effects of fungal infections on wild reptile populations. Yet, aside from Ophidiomyces ophidiicola, little is known about other mycoses affecting wild reptiles. The closely related genus Paranannizziopsis has been associated with dermatomycosis in snakes and tuataras in captive collections, and P. australasiensis was recently identified as the cause of skin infections in non-native wild panther chameleons (Furcifer pardalis) in Florida, USA. Here we describe five cases of Paranannizziopsis spp. associated with skin lesions in wild snakes in North America and one additional case from a captive snake from Connecticut, USA. In addition to demonstrating that wild Nearctic snakes can serve as a host for these fungi, we also provide evidence that the genus Paranannizziopsis is widespread in wild snakes, with cases being identified in Louisiana (USA), Minnesota (USA), Virginia (USA), and British Columbia (Canada). Phylogenetic analyses conducted on multiple loci of the fungal strains we isolated identified P. australasiensis in Louisiana and Virginia; the remaining strains from Minnesota and British Columbia did not cluster with any of the described species of Paranannizziopsis, although the strains from British Columbia appear to represent a single lineage. Finally, we designed a pan-Paranannizziopsis real-time PCR assay targeting the internal transcribed spacer region 2. This assay successfully detected DNA of all described species of Paranannizziopsis and the two potentially novel taxa isolated in this study and did not cross-react with closely related fungi or other fungi commonly found on the skin of snakes. The assay was 100% sensitive and specific when screening clinical (skin tissue or skin swab) samples, although full determination of the assay's performance will require additional follow up due to the small number of clinical samples (n = 14 from 11 snakes) available for testing in our study. Nonetheless, the PCR assay can provide an important tool in further investigating the prevalence, distribution, and host range of Paranannizziopsis spp. and facilitate more rapid diagnosis of Paranannizziopsis spp. infections that are otherwise difficult to differentiate from other dermatomycoses.

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.

Environmental temperature influences ophidiomycosis progression and survival in experimentally challenged prairie rattlesnakes (Crotalus viridis)

Ophidiomycosis is a prevalent and intermittently pervasive disease of snakes globally caused by the opportunistic fungal pathogen, Ophidiomyces ophidiicola. Host response has yet to be fully explored, including the role of temperature in disease progression and hematologic changes. This study enrolled twelve adult prairie rattlesnakes (Crotalus viridis) in an experimental challenge with O. ophidiicola at two temperatures, 26°C (n = 6) and 20°C (n = 6). Each temperature cohort included four inoculated and two control snakes. Assessments involving physical exams, lesion swabbing, and hematology were performed weekly. Differences were observed between inoculated and control snakes in survival, behavior, clinical signs, ultraviolet (UV) fluorescence, hematologic response, and histologic lesions. All inoculated snakes held at 20°C were euthanized prior to study end date due to severity of clinical signs while only one inoculated animal in the 26°C trial met this outcome. In both groups, qPCR positive detection preceded clinical signs with regards to days post inoculation (dpi). However, the earliest appearance of gross lesions occurred later in the 20°C snakes (20 dpi) than the 26°C snakes (13 dpi). Relative leukocytosis was observed in all inoculated snakes and driven by heterophilia in the 20°C snakes, and azurophilia in the 26°C group. Histologically, 20°C snakes had more severe lesions, a lack of appropriate inflammatory response, and unencumbered fungal proliferation and invasion. In contrast, 26°C snakes had marked granulomatous inflammation with encapsulation of fungi and less invasion and dissemination. The results of this study identified that O. ophidiicola-infected rattlesnakes exposed to lower temperatures have decreased survival and more robust hematologic change, though minimal and ineffective inflammatory response at site of infection. Ophidiomycosis is a complex disease with host, pathogen, and environmental factors influencing disease presentation, progression, and ultimately, survival. This study highlighted the importance of temperature as an element impacting the host response to O. ophidiicola.

Leveraging preserved specimens of Nerodia to infer the spatiotemporal dynamics of Ophidiomyces ophidiicola via quantitative polymerase chain reaction

Ophidiomyces ophidiicola (Oo) is a fungal pathogen and the causative agent of ophidiomycosis that has affected multiple snake taxa across the United States, Europe, and Asia. Ophidiomycosis has often been referred to as an emerging infectious disease (EID); however, its status as an EID has recently come under debate. Oo infections have been confirmed in wild snake populations in Texas; however, it is unknown if the pathogen is novel (i.e., invasive) or endemic to the state. To address this knowledge gap, we conducted surveys for Oo among preserved Nerodia deposited at three university museums in Texas. First, we visually assessed snakes for signs of infection (SOI), and if SOI were present, we sampled the affected area. We then used quantitative polymerase chain reaction to diagnose the presence of Oo DNA on areas with SOI and used these data to evaluate spatiotemporal patterns of Oo prevalence. We also tested for significant spatial clusters of Oo infenction using a Bernoulli probability model as implemented in the program SatScan. We found that the proportion of snakes exhibiting SOI was constant over time while the prevalence of Oo DNA among those SOI increased across space and time. Within these data, we detected an incidence pattern consistent with an introduction and then spread. We detected six spatial clusters of Oo infection, although only one was significant. Our results support the hypothesis that Oo is an emerging, novel pathogen to Texas snakes. These data narrow the knowledge gap regarding the history of Oo infections in Texas and establish a historical record of confirmed Oo detections in several counties across the state. Thus, our results will guide future research to those areas with evidence of past Oo infections but lacking confirmation in contemporary hosts.

Incidents of snake fungal disease caused by the fungal pathogen Ophidiomyces ophidiicola in Texas

The pathogen Ophidiomyces ophidiicola, widely known as the primary cause of snake fungal disease (SFD) has been detected in Texas's naïve snakes. Our team set out to characterize O. ophidiicola's spread in eastern Texas. From December 2018 until November 2021, we sampled and screened with ultraviolet (UV) light, 176 snakes across eastern Texas and detected 27. O. ophidiicola's positive snakes using qPCR and one snake in which SFD was confirmed via additional histological examination. Upon finding the ribbon snake with clear clinical display, we isolated and cultured what we believe to be the first culture from Texas. This cultured O. ophidiicola TX displays a ring halo formation when grown on a solid medium as well as cellular autofluorescence as expected. Imaging reveals individual cells within the septated hyphae branches contain a distinct nucleus separation from neighboring cells. Overall, we have found over 1/10 snakes that may be infected in East Texas, gives credence to the onset of SFD in Texas. These results add to the progress of the disease across the continental United States.

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.

Comparative host-pathogen associations of Snake Fungal Disease in sympatric species of water snakes (Nerodia)

The ascomycete fungus Ophidiomyces ophiodiicola (Oo) is the causative agent of ophidiomycosis (Snake Fungal Disease), which has been detected globally. However, surveillance efforts in the central U.S., specifically Texas, have been minimal. The threatened and rare Brazos water snake (Nerodia harteri harteri) is one of the most range restricted snakes in the U.S. and is sympatric with two wide-ranging congeners, Nerodia erythrogaster transversa and Nerodia rhombifer, in north central Texas; thus, providing an opportunity to test comparative host-pathogen associations in this system. To accomplish this, we surveyed a portion of the Brazos river drainage (~ 400 river km) over 29 months and tested 150 Nerodia individuals for the presence of Oo via quantitative PCR and recorded any potential signs of Oo infection. We found Oo was distributed across the entire range of N. h. harteri, Oo prevalence was 46% overall, and there was a significant association between Oo occurrence and signs of infection in our sample. Models indicated adults had a higher probability of Oo infection than juveniles and subadults, and adult N. h. harteri had a higher probability of infection than adult N. rhombifer but not higher than adult N. e. transversa. High Oo prevalence estimates (94.4%) in adult N. h. harteri has implications for their conservation and management owing to their patchy distribution, comparatively low genetic diversity, and threats from anthropogenic habitat modification.

REPEATED SAMPLING OF WILD INDIVIDUALS REVEALS OPHIDIOMYCES OPHIDIICOLA INFECTION DYNAMICS IN A PENNSYLVANIA SNAKE ASSEMBLAGE

Ophidiomyces ophidiicola is an emerging fungal pathogen associated with infections in snakes across North America. Although documented in Pennsylvania, O. ophidiicola has not been found at Powdermill Nature Reserve (PNR) in southwestern Pennsylvania, where the snake assemblage has been studied since 2002 and several species have recently declined. We surveyed for O. ophidiicola and putative ophidiomycosis at PNR. We screened five species of free-ranging, wild snakes (n=34) for suspected ophidiomycosis by visually checking for dermatitis and swabbing for the presence of O. ophidiicola DNA. We found a moderate prevalence of snakes with skin lesions (n=15) but a low prevalence of snakes with O. ophidiicola DNA in traditional PCR assays (n=2). Both positive snakes belonged to the same species and only one presented with lesions. When quantitative PCR screens were performed on duplicate swabs, 19 snakes were positive for O. ophidiicola DNA, with positive individuals in two species. Mark-recapture methods revealed seasonal variability in disease dynamics for sampled snakes. One individual presented with less than five skin lesions and tested negative in May 2020, had more than five lesions with a high fungal DNA load in June 2020, and no lesions with a low fungal DNA load in July 2020. We also found that snakes sampled from under the same cover object at the same time either all tested positive or all negative, including one instance involving two species. Our results underscore the value of using multiple screening techniques for O. ophidiicola surveillance and repeated sampling of individuals to understand the dynamics of ophidiomycosis in wild populations as compared to single method and single timepoint approaches.

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.

Epidemiology of Ophidiomycosis In Lake Erie Watersnakes (Nerodia sipedon insularum)

Ophidiomycosis, caused by the fungus Ophidiomyces ophidiicola, is an infectious disease of wild and managed snakes worldwide. Lake Erie watersnakes (LEWS; Nerodia sipedon insularum) were listed as threatened under the US Endangered Species Act from 1999 to 2011 and were first diagnosed with ophidiomycosis in 2009. Our objective was to characterize the epidemiology of ophidiomycosis in LEWS. We hypothesized that the prevalence of skin lesions, O. ophidiicola DNA, and ophidiomycosis disease categories would show spatial and temporal variation and clustering, with higher prevalence at sites with greater human disturbance and prevalence increasing over time. Snakes were captured via visual encounter surveys at five sites across four islands and visually inspected for skin lesions suggestive of ophidiomycosis, and then body swabs were collected to detect O. ophidiicola DNA using the quantitative PCR assay. Each snake was assigned an ophidiomycosis category based on the presence of skin lesions and O. ophidiicola. We evaluated 837 LEWS between 2017 and 2020 and detected ophidiomycosis at all five sites. Logistic regression analysis showed temporal and spatial variation in disease, with higher risk of apparent ophidiomycosis (lesions present and O. ophidiicola detected) at Kelleys Island State Park, compared to all other sites; in May, compared to July; and in 2019, compared to 2018. The presence of emerging herbaceous wetlands, urban land change, and certain soil types increased the odds of both lesion presence and quantitative PCR detection of O. ophidiicola. Overall, ophidiomycosis epidemiology varied among sites: the disease appeared to be endemic at most sites and emerging at one site. Ongoing efforts to monitor population health and mortality associated with disease prevalence are needed to inform mitigation aimed at reducing the impact of ophidiomycosis in LEWS.

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.

Investigating the Impact of Group Holding on the Transfer of Ophidiomyces ophidiicola DNA in Free-Ranging Lake Erie Watersnakes (Nerodia sipedon insularum)

Ophidiomycosis threatens snakes worldwide. We swabbed free-ranging Lake Erie watersnakes (Nerodia sipedon insularum) for quantitative PCR detection of Ophidiomyces ophidiicola before and after group and individual holding in pillowcases. Our results indicate that group, rather than individual, holding does not significantly increase detection of O. ophidiicola DNA.

Ultraviolet Fluorescence as a Field-Applicable Screening Tool for Lesions Consistent with Ophidiomycosis in Lake Erie Watersnakes (Nerodia sipedon insularum)

Ophidiomycosis, commonly called snake fungal disease, has been linked to significant morbidity of free-ranging snakes in North America and Europe. Diagnosis of ophidiomycosis currently requires detection of skin lesions via physical exam or characteristic histopathology as well as detection of the causative agent, Ophidiomyces ophidiicola, through quantitative (q)PCR or fungal culture of a skin swab or tissue sample. While reliable, these methods require specialized training, invasive procedures (e.g., biopsy), and several days or weeks to receive results. Additionally, screening entire populations can quickly become costly. A fast, easy-to-use, cost-efficient, and sensitive screening tool is needed to optimize conservation strategies and treatment intervention. Our objective was to investigate the association between skin fluorescence under long-wave ultraviolet (UV) light (365 nm) and the detection of Ophidiomyces ophidiicola DNA using qPCR. Fifty-eight Lake Erie watersnakes (Nerodia sipedon insularum) collected in June of 2018 and 2019 from islands in western Lake Erie, Ottawa County, Ohio, US were visually inspected for skin lesions, photographed under natural light and UV light, and swabbed for qPCR analysis. Fluorescence was highly associated with the presence of skin lesions, and the presence of at least one fluorescent skin lesion was 86% sensitive and 100% specific for identifying animals with apparent ophidiomycosis, with a positive predictive value of 100%. While we recommend performing standard diagnostics along with fluorescence, our study supports the use of visual UV fluorescence identification as a preliminary, affordable, noninvasive, and field-applicable method to screen populations for ophidiomycosis.

First Report of Ophidiomycosis in a Free-Ranging California Kingsnake (Lampropeltis californiae) in California, USA

Ophidiomycosis (snake fungal disease) is an emerging threat to snake health worldwide. We report a case of disseminated ophidiomycosis in a California kingsnake (Lampropeltis californiae) from Plymouth, Amador County, California, US, which is the first report of the disease in this species and in a free-ranging snake in California.

Revisiting Ophidiomycosis (Snake Fungal Disease) After a Decade of Targeted Research

Emerging infectious diseases (EIDs) are typically characterized by novelty (recent detection) and by increasing incidence, distribution, and/or pathogenicity. Ophidiomycosis, also called snake fungal disease, is caused by the fungus Ophidiomyces ophidiicola (formerly “ophiodiicola”). Ophidiomycosis has been characterized as an EID and as a potential threat to populations of Nearctic snakes, sparking over a decade of targeted research. However, the severity of this threat is unclear. We reviewed the available literature to quantify incidence and effects of ophidiomycosis in Nearctic snakes, and to evaluate whether the evidence supports the ongoing characterization of ophidiomycosis as an EID. Data from Canada remain scarce, so we supplemented the literature review with surveys for O. ophidiicola in the Canadian Great Lakes region. Peer-reviewed reports of clinical signs consistent with ophidiomycosis in free-ranging, Nearctic snakes date back to at least 1998, and retrospective molecular testing of samples extend the earliest confirmed record to 1986. Diagnostic criteria varied among publications (n = 33), confounding quantitative comparisons. Ophidiomycosis was diagnosed or suspected in 36/121 captive snakes and was fatal in over half of cases (66.7%). This result may implicate captivity-related stress as a risk factor for mortality from ophidiomycosis, but could also reflect reporting bias (i.e., infections are more likely to be detected in captive snakes, and severe cases are more likely to be reported). In contrast, ophidiomycosis was diagnosed or suspected in 441/2,384 free-ranging snakes, with mortality observed in 43 (9.8 %). Ophidiomycosis was only speculatively linked to population declines, and we found no evidence that the prevalence of the pathogen or disease increased over the past decade of targeted research. Supplemental surveys and molecular (qPCR) testing in Ontario, Canada detected O. ophidiicola on 76 of 657 free-ranging snakes sampled across ~136,000 km². The pathogen was detected at most sites despite limited and haphazard sampling. No large-scale mortality was observed. Current evidence supports previous suggestions that the pathogen is a widespread, previously unrecognized endemic, rather than a novel pathogen. Ophidiomycosis may not pose an imminent threat to Nearctic snakes, but further research should investigate potential sublethal effects of ophidiomycosis such as altered reproductive success that could impact population growth, and explore whether shifting environmental conditions may alter host susceptibility.

Outbreak of Paranannizziopsis australasiensis Infection in Captive African Bush Vipers (Atheris squamigera)

We report the epidemiological, clinical and pathological features of an outbreak of Paranannizziopsis australasiensis (order Onygenales) in captive African bush vipers (Atheris squamigera) (ABVs) that died suddenly. The snakes had multifocal, raised, white-grey to dark brown discoloured cutaneous patches. Microscopically, all had integumentary lesions characterized by multifocal to coalescent necroheterophilic epidermitis with superficial and intraepidermal fungal elements and bacteria. Concurrent epidermal hyperplasia, hyperkeratosis and intracellular and intercellular oedema, often leading to vesiculation, and fasciitis/superficial myositis, were consistent findings in all snakes, while ulceration (9/11) and dysecdysis (5/11) varied. A panfungal polymerase chain reaction targeting the internal transcribed spacer-2 region, and gene sequencing, confirmed P. australasiensis infection in three cases. This is the first report of P. australasiensis in the USA and the first record of paranannizziopsis infection in African bush vipers. P. australasiensis should be considered in the differential diagnosis of dermatomycosis in snakes and represents a potential threat to reptile conservation programmes.

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.

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.

Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease

Ophidiomycosis (snake fungal disease) is caused by the fungus Ophidiomyces ophiodiicola and threatens snake health worldwide. It has been documented throughout the eastern United States and severe cases have recently been reported in Georgia, USA. To evaluate disease distribution and prevalence in this state, 786 free-ranging snakes were examined for skin lesions consistent with ophidiomycosis and swabbed to detect O. ophiodiicola DNA using qPCR. Sampled snakes represented 34 species and 4 families; 27.5% had skin lesions, 13.3% were positive for O. ophiodiicola DNA, and 77.8% of the qPCR positive individuals had skin lesions. This is the first report of O. ophiodiicola in five of the 22 species that were qPCR positive. Multinomial logistic regression modeling indicated that Drymarchon couperi had a higher relative risk of apparent ophidiomycosis (lesions present and qPCR positive), and the best models predicting qPCR result and ophidiomycosis category included individual factors and excluded temporal and spatial factors. Phylogeny-based bipartite network analysis showed that Nerodia erythrogaster, Nerodia taxispilota, and D. couperi had the highest prevalence of apparent ophidiomycosis; this category was more prevalent in the subfamily Colubrinae and less prevalent in Natricinae. These results provide important information about ophidiomycosis epidemiology, which has implications for snake conservation.

Pathogen Surveillance and Detection of Ranavirus (Frog virus 3) in Translocated Gopher Tortoises (Gopherus polyphemus)

Emerging pathogens may pose additional threats to already vulnerable populations of chelonians, such as gopher tortoises (Gopherus polyphemus). In response to a mortality event on a translocation site in northwest Florida, US during 2013-15, 13 gopher tortoises were necropsied and their tissues were screened for 12 pathogens, including Mycoplasma agassizii, Mycoplasma testudineum, and Frog virus 3-like ranavirus (FV3). The DNA of FV3 was detected via quantitative PCR in the gastrointestinal tract of three tortoises. Subsequently, pathogen surveillance was performed on whole blood and oral-cloacal swab samples of live translocated tortoises from two different enclosures within the site (n=68), rehabilitated tortoises from the site (n=18), and tortoises prior to release on site (n=35) during 2015-17. Mycoplasma spp. were present in all groups and years of live tortoises tested. The DNA of FV3 was detected in 15 individuals both with and without clinical signs of disease in 2016. We recaptured 20 tortoises and captured an additional 20 tortoises in 2017 for surveillance, yet FV3 DNA was no longer detected, even in those that had previously tested positive (n=7). The results of this study contribute to the epidemiology of ranavirus in chelonians and suggests that gopher tortoises could be reservoirs for FV3. We recommend that the status of Ranavirus infection should be included for health screens for gopher tortoises in translocation programs.

Snake Fungal Disease in Colubridae Snakes in Connecticut, USA in 2015 and 2017

Snake fungal disease (SFD), caused by the fungus Ophidiomyces ophiodiicola, is an emerging threat to wild snake populations in the US. Data regarding its distribution, prevalence, and population-level impacts are sparse, and more information is needed to better manage SFD in the wild. In this study, we captured 38 wild snakes of five species in Connecticut in the summers of 2015 and 2017. Skin lesions were biopsied and evaluated histologically for fungal dermatitis. At least one individual from each species was positive for SFD, and 48% of snakes sampled in 2015 and 39% of snakes sampled in 2017 were positive for SFD. A Dekay's brownsnake (Storeria dekayi dekayi) with SFD lesions, captured in the summer of 2017, extended the host range of the disease. Thus, SFD was present in wild Connecticut snakes in 2015 and 2017, which demonstrated a wide-spread distribution throughout the state.

Detectability vs. time and costs in pooled DNA extraction of cutaneous swabs: a study on the amphibian chytrid fungi

Epidemiology relies on understanding the distribution of pathogens which often can be detected through DNA-based techniques, such as quantitative Polymerase Chain Reaction (qPCR). Typically, the DNA of each individual sample is separately extracted and undergoes qPCR analysis. However, when performing field surveys and long-term monitoring, a large fraction of the samples is generally expected to be negative, especially in geographical areas still considered free of the pathogen. If pathogen detection within a population – rather than determining its individual prevalence – is the focus, work load and monetary costs can be reduced by pooling samples for DNA extraction. We test and refine a user-friendly technique where skin swabs can be pooled during DNA extraction to detect the amphibian chytrid fungi, Batrachochytrium dendrobatidis and B. salamandrivorans (Bsal). We extracted pools with different numbers of samples (from one to four swabs), without increasing reaction volumes, and each pool had one sample inoculated with a predetermined zoospore amount. Pool size did not reduce the ability to detect the two fungi, except if inoculated with extremely low zoospore amounts (one zoospore). We confirm that pooled DNA extraction of cutaneous swabs can substantially reduce processing time and costs without minimizing detection sensitivity. This is of relevance especially for the new emerging pathogen Bsal, for which pooled DNA extraction had so far not been tested and massive monitoring efforts in putatively unaffected regions are underway.

Snake fungal disease alters skin bacterial and fungal diversity in an endangered rattlesnake

Snake Fungal Disease (SFD), caused by Ophidiomyces ophiodiicola, is the most recently described fungal disease afflicting wildlife populations across North America and Europe. It has been proposed as a significant conservation threat yielding high mortality and yet much its ecology is unknown. We collected 144 skin swabs from Eastern Massasaugas (Sistrurus catenatus) in 2015 and 2016 to determine document ongoing prevalence and assess differences in microbial assemblages between positive and negative individuals. Alpha diversity of fungi was reduced in SFD positive animals, while beta diversity identified distinct assemblages of microbes between SFD-positive and -negative samples. Ophidiomyces was present on the skin of affected animals, even on body sites distant to lesions indicating that the microbiome on entire surface of the skin is altered. Ophidiomyces was not detected in any non-SFD snake. There were smaller, but significant, influences of year sampled. Bacterial genera Janthinobacterium and Serratia were significantly increased in SFD snakes, while Xylanimicrobium, Cellulosimicrobium, and Rhodococcus were the only bacterial taxa significantly reduced. The relative abundance of fungi within the orders Pleosporales and Canopdiales was reduced in SFD-positive samples, though Pyrenochaetopsis pratorum was the only species found to differ significantly. This is the first study to determine the impact that this fungal pathogen has on the skin microbiome.

Common Cutaneous Bacteria Isolated from Snakes Inhibit Growth of Ophidiomyces ophiodiicola

There is increasing concern regarding potential impacts of snake fungal disease (SFD), caused by Ophidiomyces ophiodiicola (Oo), on free-ranging snake populations in the eastern USA. The snake cutaneous microbiome likely serves as the first line of defense against Oo and other pathogens; however, little is known about microbial associations in snakes. The objective of this study was to better define the composition and immune function of the snake cutaneous microbiome. Eight timber rattlesnakes (Crotalus horridus) and four black racers (Coluber constrictor) were captured in Arkansas and Tennessee, with some snakes exhibiting signs of SFD. Oo was detected through real-time qPCR in five snakes. Additional histopathological techniques confirmed a diagnosis of SFD in one racer, the species' first confirmed case of SFD in Tennessee. Fifty-eight bacterial and five fungal strains were isolated from skin swabs and identified with Sanger sequencing. Non-metric multidimensional scaling and PERMANOVA analyses indicated that the culturable microbiome does not differ between snake species. Fifteen bacterial strains isolated from rattlesnakes and a single strain isolated from a racer inhibited growth of Oo in vitro. Results shed light on the culturable cutaneous microbiome of snakes and probiotic members that may play a role in fighting an emergent disease.

Efficient high-throughput molecular method to detect Ehrlichia ruminantium in ticks

BACKGROUND

Ehrlichia ruminantium is the causal agent of heartwater, a fatal tropical disease affecting ruminants with important economic impacts. This bacterium is transmitted by Amblyomma ticks and is present in sub-Saharan Africa, islands in the Indian Ocean and the Caribbean, where it represents a threat to the American mainland.

METHODS

An automated DNA extraction method was adapted for Amblyomma ticks and a new qPCR targeting the pCS20 region was developed to improve E. ruminantium screening capacity and diagnosis. The first step in the preparation of tick samples, before extraction, was not automated but was considerably improved by using a Tissue Lyser. The new pCS20 Sol1 qPCR and a previously published pCS20 Cow qPCR were evaluated with the OIE standard pCS20 nested PCR.

RESULTS

pCS20 Sol1 qPCR was found to be more specific than the nested PCR, with a 5-fold increase in sensitivity (3 copies/reaction vs 15 copies/reaction), was less prone to contamination and less time-consuming. As pCS20 Sol1 qPCR did not detect Rickettsia, Anasplasma and Babesia species or closely related species such as Panola Mountain Ehrlichia, E. chaffeensis and E. canis, its specificity was also better than Cow qPCR. In parallel, a tick 16S qPCR was developed for the quality control of DNA extraction that confirmed the good reproducibility of the automated extraction. The whole method, including the automated DNA extraction and pCS20 Sol1 qPCR, was shown to be sensitive, specific and highly reproducible with the same limit of detection as the combined manual DNA extraction and nested PCR, i.e. 6 copies/reaction. Finally, 96 samples can be tested in one day compared to the four days required for manual DNA extraction and nested PCR.

CONCLUSIONS

The adaptation of an automated DNA extraction using a DNA/RNA viral extraction kit for tick samples and the development of a new qPCR increased the accuracy of E. ruminantium epidemiological studies, as well as the diagnostic capabilities and turn-over time for surveillance of heartwater. This new method paves the way for large-scale screening of other bacteria and viruses in ticks as well as genetic characterization of ticks and tick-pathogen coevolution studies.

Detection of Snake Fungal Disease Due to Ophidiomyces ophiodiicola in Virginia, USA

Snake fungal disease (SFD) is an emerging disease of wildlife believed to be caused by Ophidiomyces ophiodiicola. Although geographic and host ranges have yet to be determined, this disease is characterized by crusty scales, superficial pustules, and subcutaneous nodules, with subsequent morbidity and mortality in some snake species. To confirm the presence of SFD and O. ophiodiicola in snakes of eastern Virginia, US, we clinically examined 30 free-ranging snakes on public lands from April to October 2014. Skin biopsy samples were collected from nine snakes that had gross lesions suggestive of SFD; seven of these biopsies were suitable for histologic interpretation, and eight were suitable for culture and PCR detection of O. ophiodiicola. Seven snakes had histologic features consistent with SFD and eight were positive for O. ophiodiicola by PCR or fungal culture.

Snake fungal disease caused by Ophidiomyces ophiodiicola in a free-ranging mud snake (Farancia abacura)

Snake fungal disease is an emerging infectious disease caused by the fungus Ophidiomyces ophiodiicola leading to severe dermatitis and facial disfiguration in numerous free-ranging and captive snakes. A free-ranging mud snake ( Farancia abacura) from Bulloch County, Georgia, was presented for autopsy because of facial swelling and emaciation. Extensive ulceration of the skin, which was especially severe on the head, and retained shed were noted on external examination. Microscopic examination revealed severe heterophilic dermatitis with intralesional fungal hyphae and arthroconidia consistent with O. ophiodiicola. A skin sample incubated on Sabouraud dextrose agar yielded a white-to-tan powdery fungal culture that was confirmed to be O. ophiodiicola by polymerase chain reaction and sequence analysis. Heavy infestation with adult tapeworms ( Ophiotaenia faranciae) was present within the intestine. Various bacterial and fungal species, interpreted to either be secondary invaders or postmortem contaminants, were associated with oral lesions. Although the role of these other organisms in the overall health of this individual is not known, factors such as concurrent infections or immunosuppression should be considered in order to better understand the overall manifestation of snake fungal disease, which remains poorly characterized in its host range and geographic distribution.

Detection of Ophidiomyces, the Causative Agent of Snake Fungal Disease, in the Eastern Massasauga ( Sistrurus catenatus ) in Michigan, USA, 2014

Snake fungal disease (SFD), caused by Ophidiomyces ophiodiicola, threatens free-ranging snake populations across the US. We assayed 112 swabs from 102 individual eastern massasaugas ( Sistrurus catenatus ) at three locations in Michigan in 2014 for Ophidiomyces using quantitative PCR (qPCR). We observed a 12.7% qPCR prevalence of skin lesions. Individuals at each site had lesions, and occurrence of skin lesions was not significantly different between sites. We detected Ophidiomyces DNA at each of the three sites in five individuals (4.9%). We found no difference in detection probabilities between sites; however, snakes with dermatitis had higher Ophidiomyces DNA detection probabilities (P=0.15±0.08 SE) than snakes without dermatitis (P=0.02±0.01 SE, P=0.026). The emergence of SFD mortalities has potentially serious consequences for the viability of the eastern massasauga in Michigan. Future work should track temporal patterns in vital rates and health parameters, link health data to body condition indices for individual snakes, and conduct a "hotspot" analysis to examine health on a landscape scale.

HEMATOLOGY IN AN EASTERN MASSASAUGA (SISTRURUS CATENATUS) POPULATION AND THE EMERGENCE OF OPHIDIOMYCES IN ILLINOIS, USA

Disease events are threatening wildlife populations across North America. Specifically, mortality events due to Ophidiomyces (snake fungal disease; SFD) have been observed recently in snakes in Illinois, US. We investigated the health of a population of eastern massasaugas ( Sistrurus catenatus ) in south-central Illinois using 1) a meta-analysis of hematologic findings from 2004, 2011, 2013, and 2014; 2) a determination of the prevalence of SFD in snakes examined in 2013 and 2014; and 3) the examination of 184 museum specimens collected from 1999-2013 for signs and presence of SFD. For the meta-analysis and prevalence of SFD, hematologic analytes were reduced to three principle components that explained 67.5% of the cumulative variance. There were significant differences among one principle component (total white blood cell counts, monocytes, lymphocytes, and basophils) across years when it was highest in 2004 and 2014. The top general linear model explaining the difference in principle components included the main effects of year and stage, body condition index (BCI), and the interaction between stage and BCI. The prevalence of SFD was 18% (n=7) in 2013 and 24% (n=11) in 2014, and no hematologic analytes were associated with SFD. In museum specimens, Ophidiomyces DNA was first detected from an individual collected in 2000. Studies such as these, integrating multiple modalities of health, can elucidate the epidemiology of diseases that may pose conservation threats.

Development of Snake Fungal Disease after Experimental Challenge with Ophidiomyces ophiodiicola in Cottonmouths (Agkistrodon piscivorous)

Snake fungal disease (SFD) is a clinical syndrome associated with dermatitis, myositis, osteomyelitis, and pneumonia in several species of free-ranging snakes in the US. The causative agent has been suggested as Ophidiomyces ophiodiicola, but other agents may contribute to the syndrome and the pathogenesis is not understood. To understand the role of O. ophiodiicola in SFD, a cottonmouth snake model of SFD was designed. Five cottonmouths (Agkistrodon piscivorous) were experimentally challenged by nasolabial pit inoculation with a pure culture of O. ophiodiicola. Development of skin lesions or facial swelling at the site of inoculation was observed in all snakes. Twice weekly swabs of the inoculation site revealed variable presence of O. ophiodiicola DNA by qPCR in all five inoculated snakes for 3 to 58 days post-inoculation; nasolabial flushes were not a useful sampling method for detection. Inoculated snakes had a 40% mortality rate. All inoculated snakes had microscopic lesions unilaterally on the side of the swabbed nasolabial pit, including erosions to ulcerations and heterophilic dermatitis. All signs were consistent with SFD; however, the severity of lesions varied in individual snakes, and fungal hyphae were only observed in 3 of 5 inoculated snakes. These three snakes correlated with post-mortem tissue qPCR evidence of O. ophiodiicola. The findings of this study conclude that O. ophiodiicola inoculation in a cottonmouth snake model leads to disease similar to SFD, although lesion severity and the fungal load are quite variable within the model. Future studies may utilize this model to further understand the pathogenesis of this disease and develop management strategies that mitigate disease effects, but investigation of other models with less variability may be warranted.