Novel Rickettsia and host records for argasid ticks, including Alveonasus cooleyi, on wild mammals in Baja California, Mexico.

We conducted surveillance of mammals to investigate their associations with argasid ticks and tick-borne pathogens. During 2021, a total of 20 wild carnivores and 57 lagomorphs were sampled, and 39 argasid ticks belonging to two species were collected. All mammals and ticks were tested by molecular assays to detect Borrelia and Rickettsia infections. Nine ticks identified as Otobius megnini were collected from two coyotes (Canis latrans) and 30 Alveonasus cooleyi (McIvor 1941) were collected from six bobcats (Lynx rufus) and one rabbit (Sylvilagus auduboni). We detected Rickettsia spp. DNA in 21 of the 27 (77.8%) tested Av. cooleyi and none of the O. megnini. No ticks were PCR-positive for borreliae and all mammals were PCR-negative for both pathogen genera. Phylogenetic analysis based on gltA, htrA, and 16 S rRNA targets revealed that all rickettsiae from Av. cooleyi clustered with ancestral group rickettsiae, likely representing a novel species of possibly endosymbiotic Rickettsia. The significance of Av. cooleyi and the newly identified Rickettsia sp. to the health of wildlife is unknown, and further work is indicated to determine whether they may be relevant to public health or carnivore conservation.

Subcutaneous choriocarcinomas in captive Amargosa voles (Microtus californicus scirpensis).

Spontaneous choriocarcinomas are rare, highly vascular, malignant trophoblastic tumors that occur in humans and animals. This report describes the unusual spontaneous presentation of 4 choriocarcinomas within the subcutaneous tissues of 4, multiparous but nongravid, Amargosa voles (Microtus californicus scirpensis) from a captive breeding colony. Two subcutaneous neoplasms were composed of multifocal discohesive and infiltrative aggregates of medium to large trophoblasts and cytotrophoblasts within a fibrovascular stroma. Neoplastic cells were associated with variably sized thrombi and cavitary areas of hemorrhage and necrosis. Two subcutaneous tumors were predominantly composed of expansile, blood-filled, cystic spaces lined by neoplastic cytotrophoblasts and occasionally contained medium to large trophoblasts. Trophoblasts and cytotrophoblasts were positive for pancytokeratin and cytokeratin 8/18, negative for alpha-fetoprotein, and contained intracytoplasmic Periodic acid-Schiff (PAS)-positive glycogen in all 4 tumors. In species with hemochorial placentation, migration of trophoblasts into maternal circulation with embolization to distant nonreproductive tissues occurs and may explain the unusual subcutaneous distribution of these 4 tumors. The 2 multiloculated paucicellular tumors may represent an early stage of neoplastic transformation. To the authors' knowledge, this is the first report characterizing choriocarcinomas in extrareproductive sites in rodents.

Spatial distribution patterns of tick community structure in sympatric jaguars (Panthera onca) and pumas (Puma concolor) from three ecoregions in Mexico.

We examined tick communities on wild felid hosts in three ecoregions of Mexico. We collected 186 ticks of 7 species from 10 pumas (Puma concolor) and 9 jaguars (Panthera onca). Tick community composition varied across the ecoregions, and across host species within each region. Overall, Ixodes affinis, Amblyomma ovale, and Amblyomma tenellum were the most abundant species; however, only the latter two ticks were distributed across all three ecoregions, while I. affinis, along with Ixodes spinipalpis, Amblyomma inornatum, and Amblyomma parvum were restricted to more limited geographical regions. Ixodes affinis occurred strictly in southern tropical rainforest ecoregions and was significantly more abundant in Selva Lacandona compared with the Yucatán Peninsula. Amblyomma ovale was significantly more common in the tropical dry forest in the Pacific coastal ecoregion. Amblyomma tenellum abundance tended to be higher on jaguars, while I. affinis abundance was higher on pumas. Regional distribution patterns of some tick species (e.g., I. affinis and I. spinipalpis) may be determined by off-host environmental conditions rather than host factors. In contrast, at the local scale, occurrence and abundance of some tick species (e.g., A. tenellum, A. ovale and Rhipicephalus microplus) might be driven by ecological-host factors, such as habitat use or predator-prey relationships.

Tick Microbiomes in Neotropical Forest Fragments Are Best Explained by Tick-Associated and Environmental Factors Rather than Host Blood Source.

The composition of tick microbiomes varies both within and among tick species. Whether this variation is intrinsic (related to tick characteristics) or extrinsic (related to vertebrate host and habitat) is poorly understood but important, as microbiota can influence the reproductive success and vector competence of ticks. We aimed to uncover what intrinsic and extrinsic factors best explain the microbial composition and taxon richness of 11 species of neotropical ticks collected from eight species of small mammals in 18 forest fragments across central Panama. Microbial richness varied among tick species, life stages, and collection sites but was not related to host blood source. Microbiome composition was best explained by tick life stage, with bacterial assemblages of larvae being a subset of those of nymphs. Collection site explained most of the bacterial taxa with differential abundance across intrinsic and extrinsic factors. Francisella and Rickettsia were highly prevalent, but their proportional abundance differed greatly among tick species, and we found both positive and negative cooccurrence between members of these two genera. Other tick endosymbionts (e.g., Coxiella and Rickettsiella) were associated with specific tick species. In addition, we detected Anaplasma and Bartonella in several tick species. Our results indicate that the microbial composition and richness of neotropical ticks are principally related to intrinsic factors (tick species and life stage) and collection site. Taken together, our analysis informs how tick microbiomes are structured and can help anchor our understanding of tick microbiomes from tropical environments more broadly.IMPORTANCE Blood-feeding arthropod microbiomes often play important roles in disease transmission, yet the factors that structure tick microbial communities in the Neotropics are unknown. Utilizing ticks collected from live animals in neotropical forest fragments, this study teases apart the contributions of intrinsic and extrinsic tick-associated factors on tick microbial composition as well as which specific microbes contribute to differences across tick species, tick life stages, the mammals they fed on, and the locations from where they were sampled. Furthermore, this study provides revelations of how notable tick-associated bacterial genera are interacting with other tick-associated microbes as well as the forest animals they encounter.

Demodectic mange in threatened southern sea otters (Enhydra lutris nereis).

BACKGROUND: Southern sea otters (Enhydra lutris nereis) rely on intact pelage for thermoregulation, and thus clinically significant demodicosis and associated alopecia can cause morbidity and death. HYPOTHESIS/OBJECTIVES: This study aimed to describe lesions associated with follicular Demodex sp. infestation, estimate the prevalence and intensity of infestation, describe mite distribution across key anatomical regions, and assess mite presence or absence in relation to lesions and host risk factors. ANIMALS: Twenty necropsied, wild southern sea otters that stranded along the central California coast from 2005 to 2018. METHODS AND MATERIALS: Grossly normal and abnormal integument from the head, perineum, genitals, mamillary papillae and limbs was assessed microscopically for mites and mite-associated pathological findings. RESULTS: Intrafollicular mites were observed in the integument of 55% of otters and 20% had clinical demodicosis. Demodicosis was considered to be contributory to death or euthanasia in two cases. Although Demodex sp. mites often were observed microscopically in grossly normal skin, the presence of multiple densely-packed intrafollicular mites generally was associated with pigmentary incontinence, ectatic follicles, lymphoplasmacytic perifolliculitis, and neutrophilic and lymphoplasmacytic, dermal inflammation. Other findings included epidermal hyperplasia, orthokeratotic hyperkeratosis of epidermis and follicular epithelium, concurrent pyoderma and cell necrosis. Perioral integument, especially of the chin, had the highest prevalence of mites and the highest mite density, suggesting facial contact as a means of mite transmission. CONCLUSIONS AND CLINICAL IMPORTANCE: Our research confirmed demodectic mange as a contributor to morbidity and mortality in sea otters, with important implications for clinical care, rehabilitation and conservation.

USE OF FLUMETHRIN-IMPREGNATED COLLARS TO MANAGE AN EPIDEMIC OF SARCOPTIC MANGE IN AN URBAN POPULATION OF ENDANGERED SAN JOAQUIN KIT FOXES (VULPES MACROTIS MUTICA).

Sarcoptic mange epidemics can have long-lasting impacts on susceptible wildlife populations, potentially contributing to local population declines and extirpation. Since 2013, there have been 460 reported cases of sarcoptic mange in an urban population of endangered San Joaquin kit foxes (Vulpes macrotis mutica) in Bakersfield, CA, with many of them resulting in fatality. As part of a multifaceted response to mitigate mange-caused mortalities and reduce this conservation threat, a 2-yr randomized field trial was conducted to assess the efficacy of long-acting flumethrin collars against sarcoptic mange in kit foxes. Thirty-five kit foxes living in a high-density population on a college campus were captured, examined, administered selamectin, and each fox randomly assigned to either receive a flumethrin collar placed within a VHF radio collar or a VHF radio collar without flumethrin. The survival and mange-infestation status of study animals was monitored via radio telemetry, remote cameras, and periodic recapture examinations and compared among treated and control kit foxes using a Cox proportional hazards model. The average time to onset of mange for treated kit foxes (176 days) was similar to controls (171 days) and treatment with flumethrin did not significantly reduce mange risk for all kit foxes. Kit foxes that had a mild mange infestation at the beginning of the study were four times more likely to develop mange again, regardless of flumethrin treatment, compared with kit foxes that had no signs at initial recruitment. This study demonstrates an approach to evaluating population-level protection and contributes to the limited literature on efficacy, safety, and practicality of acaricides in free-ranging wildlife.

DISEASE AND PATHOLOGICAL CONDITIONS OF AN ENDANGERED RODENT, MICROTUS CALIFORNICUS SCIRPENSIS, IN A CAPTIVE-REARING FACILITY AND IN THE WILD.

Causes of morbidity and mortality and a survey of infectious disease agents were collated from wild and colony-raised endangered Amargosa voles (Microtus californicus scirpensis). Six voles from the wild and 295 voles in the captive-breeding colony were included in the study upon identification of an infectious agent during screening, identification of clinical signs of disease, or finding a pathological condition or infectious agent on necropsy. Findings included 28 significant or incidental pathological conditions of seven organ systems and 19 parasitic, viral, bacterial, or fungal agents. Several voles captured in the wild had fungal osteomyelitis of the tail that disseminated systemically in a vole brought from the wild to the colony and may have been caused by a Penicillium sp. Three voles reintroduced from the colony to the wild experienced inanition and subsequent severe hepatic and moderate renal tubular lipidosis. The most common significant pathological conditions in colony-reared voles were chronic interstitial nephritis with proteinosis; cardiomyopathy; trichobezoars that, in intestines or cecocolic junctions, sometimes induced local rupture or infarction with peritonitis; multifocal gastrointestinal ulceration and colibacillosis; acute renal tubular necrosis or nephritis; sepsis; hepatic and renal lipidosis; molar apical elongation sometimes progressing to invasion of the calvarium; and mammary tumors. Uncommon diagnoses included intervertebral disc disease; microvascular dysplasia; and multifocal bacterial abscessation. Common or clinically important infectious agents included Demodex sp. mites in hair follicles, Demodex sp. in esophageal mucosa, and an outbreak of tropical rat mites thought to have been introduced via the straw bedding; gastrointestinal Helicobacter sp.; attaching and effacing Escherichia coli; and Citrobacter braakii, a possible zoonotic bacterium. This survey of species-specific diseases and pathogens was possible because the established health surveillance program that is part of the species recovery plan allowed for monitoring of voles throughout the duration of their natural life spans in captivity.

Rickettsia africae and Novel Rickettsial Strain in Amblyomma spp. Ticks, Nicaragua, 2013.

We report molecular detection of Rickettsia africae in Amblyomma ovale ticks from Nicaragua and a novel rickettsial strain in an A. triste tick. Of 146 ticks from dogs, 16.4% were Rickettsia PCR positive. The presence of Rickettsia spp. in human-biting ticks in Nicaragua may pose a public health concern.

Molecular Confirmation of Rocky Mountain Spotted Fever Epidemic Agent in Mexicali, Mexico.

Since 2008, a large epidemic of Rocky Mountain spotted fever has been emerging among humans and dogs in Mexicali, adjacent to the United States in Baja California, Mexico. We molecularly confirmed the causative agent; this information can be used to study the origin and dynamics of the epidemic.

Urbanization and anticoagulant poisons promote immune dysfunction in bobcats.

Understanding how human activities influence immune response to environmental stressors can support biodiversity conservation across increasingly urbanizing landscapes. We studied a bobcat (Lynx rufus) population in urban southern California that experienced a rapid population decline from 2002-2005 due to notoedric mange. Because anticoagulant rodenticide (AR) exposure was an underlying complication in mange deaths, we aimed to understand sublethal contributions of urbanization and ARs on 65 biochemical markers of immune and organ function. Variance in immunological variables was primarily associated with AR exposure and secondarily with urbanization. Use of urban habitat and AR exposure has pervasive, complex and predictable effects on biochemical markers of immune and organ function in free-ranging bobcats that include impacts on neutrophil, lymphocyte and cytokine populations, total bilirubin and phosphorus. We find evidence of both inflammatory response and immune suppression associated with urban land use and rat poison exposure that could influence susceptibility to opportunistic infections. Consequently, AR exposure may influence mortality and has population-level effects, as previous work in the focal population has revealed substantial mortality caused by mange infection. The secondary effects of anticoagulant exposure may be a worldwide, largely unrecognized problem affecting a variety of vertebrate species in human-dominated environments.

Apical Elongation of Molar Teeth in Captive Microtus Voles.

Molar apical elongation (MAE) was the leading cause for euthanasia or death in a captive breeding colony of endangered Amargosa voles ( Microtus californicus scirpensis). Clinical signs included ocular discharge, abnormal mastication, dyspnea, abnormal mentation, weight loss, and death. Although the severity varied, all molars in all quadrants were affected. When severe, the overgrown molar reserve crown and apex protruded into the nasal meatuses, the orbit, the calvarial vault and through the ventral margin of the mandible. Overall prevalence in the colony was 63% (92/146 voles) and increased to 77% in aged voles (>1 year). Mean age of onset was 5.3 months (1.7-11.2 months). Progression to extreme severity occurred over 1 to 3 months. Mean survival was 10.9 months (7.1-21.7 months). Histologically, the lesion was characterized by odontogenic hyperplasia and dysplasia. MAE was also documented in museum specimens of 2 other M. californicus subspecies ( M. californicus californicus, M. californicus vallicola) and 3 other Microtus species ( M. montanus, M. pennsylvanicus, M. socialis). In the M. californicus californicus collection, overall prevalence was 35.1% (129/368 skulls) and increased to 77.3% in aged voles (>1 year). A probable genetic influence was identified in the museum collection of M. californicus californicus. The etiopathogenesis of MAE is likely multifactorial, due to (1) inherent continuous odontogenic proliferation, (2) inadequate occlusal attrition, and (3) possible heritable disease susceptibility. In captivity, dietary or other management of occlusal attrition to prevent or delay MAE is a fundamental concern.

Successful care and propagation of the endangered amargosa vole (Microtus californicus scirpensis) in captivity.

The Amargosa vole (Microtus californicus scirpensis) is a highlyendangered rodent endemic to a small stretch of the California portion of the Amargosa River basin in Inyo County's Mojave Desert. Although the Amargosa vole has survived in this naturally fragmented ecosystem for thousands of years, recent habitat degradation due to land development, water drainage, and marsh exploitation has further isolated the species and reduced its available habitat. As part of a conservation effort to preserve the species, a captive breeding population was established in 2014 to serve as an insurance colony and as a source of individuals to release into the wild as restored habitat becomes available. As this is the only captive colony for this species, there is little published information about appropriate care and husbandry for the Amargosa vole. Here we provide information about behavior, diet, reproduction, drug sensitivities, and diseases that affect successful captive care. We also provide recommendations for housing and disease management to preserve natural behaviors and defenses in captive-born animals.

ERADICATION OF A TROPICAL RAT MITE ( ORNITHONYSSUS BACOTI) INFESTATION FROM A CAPTIVE COLONY OF ENDANGERED AMARGOSA VOLES ( MICROTUS CALIFORNICUS SCIRPENSIS).

Staff at a university laboratory responsible for management of a captive insurance colony of endangered Amargosa voles ( Microtus californicus scirpensis) discovered an outbreak of tropical rat mites ( Ornithonyssus bacoti) infesting 106 voles. This bloodsucking mesostigmatid mite typically occurs in laboratory settings and can cause weight loss, wounds, or other negative impacts on health. The source of the infestation was likely feral rodents, and the route was suspected to be straw bedding. Twenty-nine of the 106 (27.4%) infested voles developed ulcerated dorsal skin lesions that resolved when treated with topical selamectin. A triad approach was implemented to eradicate the mites, consisting of environmental management, individual animal treatment, and training. Voles were moved individually into a clean room containing only autoclaved materials (including straw), cages were treated with permethrin-impregnated cotton, treatment order was instituted to avoid transferring mites, and voles coming from outside were quarantined. All animals in an infested room were treated with topical selamectin, and personnel were trained on risks and new procedures. No adverse effects from the use of selamectin were identified, and this efficient protocol does not require the long-term use of acaricides. This report documents infestation of an endangered rodent with an exotic parasite, safe use of permethrin and selamectin in this species, and comprehensive management to manage a large infestation.

Greater Species Richness of Bacterial Skin Symbionts Better Suppresses the Amphibian Fungal Pathogen Batrachochytrium Dendrobatidis.

The symbiotic microbes that grow in and on many organisms can play important roles in protecting their hosts from pathogen infection. While species diversity has been shown to influence community function in many other natural systems, the question of how species diversity of host-associated symbiotic microbes contributes to pathogen resistance is just beginning to be explored. Understanding diversity effects on pathogen resistance could be particularly helpful in combating the fungal pathogen Batrachochytrium dendrobatidis (Bd) which has caused dramatic population declines in many amphibian species and is a major concern for amphibian conservation. Our study investigates the ability of host-associated bacteria to inhibit the proliferation of Bd when grown in experimentally assembled biofilm communities that differ in species number and composition. Six bacterial species isolated from the skin of Cascades frogs (Rana cascadae) were used to assemble bacterial biofilm communities containing 1, 2, 3, or all 6 bacterial species. Biofilm communities were grown with Bd for 7 days following inoculation. More speciose bacterial communities reduced Bd abundance more effectively. This relationship between bacterial species richness and Bd suppression appeared to be driven by dominance effects-the bacterial species that were most effective at inhibiting Bd dominated multi-species communities-and complementarity: multi-species communities inhibited Bd growth more than monocultures of constituent species. These results underscore the notion that pathogen resistance is an emergent property of microbial communities, a consideration that should be taken into account when designing probiotic treatments to reduce the impacts of infectious disease.

Detection of Lyme Disease Bacterium, Borrelia burgdorferi sensu lato, in Blacklegged Ticks Collected in the Grand River Valley, Ontario, Canada.

We document the presence of blacklegged ticks, Ixodes scapularis, in the Grand River valley, Centre Wellington, Ontario. Overall, 15 (36%) of 42 I. scapularis adults collected from 41 mammalian hosts (dogs, cats, humans) were positive for the Lyme disease bacterium, Borrelia burgdorferi sensu lato (s.l.). Using real-time PCR testing and DNA sequencing of the flagellin (fla) gene, we determined that Borrelia amplicons extracted from I. scapularis adults belonged to B. burgdorferi sensu stricto (s.s.), which is pathogenic to humans and certain domestic animals. Based on the distribution of I. scapularis adults within the river basin, it appears likely that migratory birds provide an annual influx of I. scapularis immatures during northward spring migration. Health-care providers need to be aware that local residents can present with Lyme disease symptoms anytime during the year.

Established Population of Blacklegged Ticks with High Infection Prevalence for the Lyme Disease Bacterium, Borrelia burgdorferi Sensu Lato, on Corkscrew Island, Kenora District, Ontario.

We document an established population of blacklegged ticks, Ixodes scapularis, on Corkscrew Island, Kenora District, Ontario, Canada. Primers of the outer surface protein A (OspA) gene, the flagellin (fla) gene, and the flagellin B (flaB) gene were used in the PCR assays to detect Borrelia burgdorferi sensu lato (s.l.), the Lyme disease bacterium. In all, 60 (73%) of 82 adult I. scapularis, were infected with B. burgdorferi s.l. As well, 6 (43%) of 14 unfed I. scapularis nymphs were positive for B. burgdorferi s.l. An I. scapularis larva was also collected from a deer mouse, and several unfed larvae were gathered by flagging leaf litter. Based on DNA sequencing of randomly selected Borrelia amplicons from six nymphal and adult I. scapularis ticks, primers for the flagellin (fla) and flagellin B (flaB) genes reveal the presence of B. burgdorferi sensu stricto (s.s.), a genospecies pathogenic to humans and certain domestic animals. We collected all 3 host-feeding life stages of I. scapularis in a single year, and report the northernmost established population of I. scapularis in Ontario. Corkscrew Island is hyperendemic for Lyme disease and has the highest prevalence of B. burgdorferi s.l. for any established population in Canada. Because of this very high infection prevalence, this population of I. scapularis has likely been established for decades. Of epidemiological significance, cottage owners, island visitors, outdoors enthusiasts, and medical professionals must be vigilant that B. burgdorferi s.l.-infected I. scapularis on Corkscrew Island pose a serious public health risk.

Host, habitat and climate preferences of Ixodes angustus (Acari: Ixodidae) and infection with Borrelia burgdorferi and Anaplasma phagocytophilum in California, USA.

The Holarctic tick Ixodes angustus is a competent vector for Borrelia burgdorferi, the etiologic agent of Lyme disease, and possibly Anaplasma phagocytophilum, the etiologic agent of granulocytic anaplasmosis, as well. From 2005 to 2013, we collected host-feeding I. angustus individuals from live-trapped small mammals and by flagging vegetation from 12 study sites in northern and central California, and tested for B. burgdorferi sensu lato, A. phagocytophilum, and Rickettsia spp. DNA by real-time PCR. Among 261 I. angustus collected (259 from hosts and two by flagging), the most common hosts were tree squirrels (20 % of ticks) and chipmunks (37 %). The PCR-prevalence for A. phagocytophilum and B. burgdorferi in ticks was 2 % and zero, respectively. The minimum infection prevalence on pooled DNA samples was 10 % for Rickettsia spp. DNA sequencing of the ompA gene identified this rickettsia as Candidatus Rickettsia angustus, a putative endosymbiont. A zero-inflated negative binomial mixed effects model was used to evaluate geographical and climatological predictors of I. angustus burden. When host species within study site and season within year were included in the model as nested random effects, all significant variables revealed that I. angustus burden increased as temperature decreased. Together with published data, these findings suggest that I. angustus is a host generalist, has a broad geographic distribution, is more abundant in areas with lower temperature within it's range, and is rarely infected with the pathogens A. phagocytophilum and B. burgdorferi.

Ectoparasites of Microtus californicus and Possible Emergence of an Exotic Ixodes Species Tick in California.

California voles (Microtus californicus Peale) harbor fleas and ticks, may be infected with vector-borne pathogens, and could themselves suffer from disease and serve as a source of infection for people and other animals. Here we summarize publications, museum archives, and recent records of ticks and fleas from California voles. There have been 18 flea species reported on California voles with geographic locations reported for 13. During recent statewide surveys, we found six flea species, with the highest species richness in Humboldt County. We found three of five previously reported tick species as well as a tick resembling the eastern North American tick Ixodes minor Neumann (which we here designate Ixodes "Mojave morphotype") on isolated Amargosa voles and Owens Valley voles (Microtus californicus vallicola Bailey) in Inyo County in 2012 and 2014. Additional incidental observations of this Mojave morphotype tick were on a western harvest mouse (Reithrodontomys megalotis Baird) at the Mojave site and a montane vole (Microtus montanus Peale) in the Owens Valley, both in March, 2014. We cannot rule out that this tick species has been present in remote areas of California but gone unrecognized, but these data are consistent with recent introduction of this tick, possibly from migrating birds. Changes in the ectoparasite fauna suggest changing ecologies of vectors and vector-borne pathogens that could influence animals and people as well.

Itraconazole treatment reduces Batrachochytrium dendrobatidis prevalence and increases overwinter field survival in juvenile Cascades frogs.

The global spread of the fungal pathogen Batrachochytrium dendrobatidis (Bd) has led to widespread extirpation of amphibian populations. During an intervention aimed at stabilizing at-risk populations, we treated wild-caught Cascades frogs Rana cascadae with the antifungal drug itraconazole. In fall 2012, we collected 60 recently metamorphosed R. cascadae from 1 of the 11 remnant populations in the Cascades Mountains (CA, USA). Of these, 30 randomly selected frogs were treated with itraconazole and the other 30 frogs served as experimental controls; all were released at the capture site. Bd prevalence was low at the time of treatment and did not differ between treated frogs and controls immediately following treatment. Following release, Bd prevalence gradually increased in controls but not in treated frogs, with noticeable (but still non-significant) differences 3 wk after treatment (27% [4/15] vs. 0% [0/13]) and strong differences 5 wk after treatment (67% [8/12] vs. 13% [1/8]). We did not detect any differences in Bd prevalence and load between experimental controls and untreated wild frogs during this time period. In spring 2013, we recaptured 7 treated frogs but none of the experimental control frogs, suggesting that over-winter survival was higher for treated frogs. The itraconazole treatment did appear to reduce growth rates: treated frogs weighed 22% less than control frogs 3 wk after treatment (0.7 vs. 0.9 g) and were 9% shorter than control frogs 5 wk after treatment (18.4 vs. 20.2 mm). However, for critically small populations, increased survival of the most at-risk life stage could prevent or delay extinction. Our results show that itraconazole treatment can be effective against Bd infection in wild amphibians, and therefore the beneficial effects on survivorship may outweigh the detrimental effects on growth.