Raptors may serve as both intermediate and definitive hosts for Sarcocystis spp. Past research has documented fatal encephalitis in raptors caused by various Sarcocystis spp., whereas other surveys have found a high prev...Raptors may serve as both intermediate and definitive hosts for Sarcocystis spp. Past research has documented fatal encephalitis in raptors caused by various Sarcocystis spp., whereas other surveys have found a high prevalence of tissue cysts without evidence of disease. Little is known about the prevalence of Sarcocystis in raptors in the eastern USA. The aim of this study was to determine the occurrence of tissue cysts and histopathologic changes associated with Sarcocystis spp. infection in raptors in eastern Tennessee. Tissues of 33 raptors from Tennessee, USA, were assessed with histopathologic examination. Cysts consistent with Sarcocystis spp. were present in the heart, skeletal, or tracheal muscle of 11 (33%) raptors, without any associated inflammation. Tissues from histopathologic-positive raptors were then tested with PCR targeting of the 18S rRNA gene of Sarcocystis. Sequence analysis of PCR products revealed that six raptors had sequences most similar to Sarcocystis falcatula, and two had sequences most similar to Sarcocystis halieti. In addition, one S. falcatula-positive Bald Eagle (Haliaeetus leucocephalus) had lymphoplasmacytic meningoencephalitis and was positive via immunohistochemistry for eastern equine encephalitis virus. Our study supports findings in other geographic regions that raptors commonly serve as hosts for Sarcocystis spp. without evidence of associated disease.
Pansteatitis can be fatal and contribute to wild crocodilian population declines. We documented lesions consistent with pansteatitis in two wild American alligators (Alligator mississippiensis) from South Carolina and Mi...Pansteatitis can be fatal and contribute to wild crocodilian population declines. We documented lesions consistent with pansteatitis in two wild American alligators (Alligator mississippiensis) from South Carolina and Mississippi, USA. These findings extend our knowledge of pansteatitis in wild crocodilians, for which few observations exist beyond Nile crocodiles (Crocodylus niloticus).
The American bison (Bison bison) is an ecologically, economically, and culturally significant species that is exceptionally vulnerable to disease caused by Mycoplasma bovis. In contrast to livestock in which M. bovis is...The American bison (Bison bison) is an ecologically, economically, and culturally significant species that is exceptionally vulnerable to disease caused by Mycoplasma bovis. In contrast to livestock in which M. bovis is one of many infectious agents comprising the bovine respiratory disease complex, infection in bison is characterized by severe pneumonia and potential for systemic disease in the absence of coinfecting pathogens. In bison, morbidity and mortality are highest in adult cows, whereas calves and yearlings infrequently present with clinical disease. The infection dynamics of M. bovis in young bison exposed during an outbreak have not been fully characterized. Herein, we describe a severe outbreak of M. bovis in a closed, extensively managed herd from which we established a cohort of young bison for longitudinal observation, sampling, and testing. Our findings indicate that M. bovis can colonize the nasopharynx of calves and yearlings during an outbreak, often without causing apparent clinical signs. Although some animals cleared the infection during a 12-mo follow-up study, others remained PCR and culture positive, highlighting the potential for asymptomatic carriage in bison calves as a source of subsequent outbreaks. Using a paired swabbing approach, we show that sampling the superficial nasal cavity is adequate for detection of M. bovis during an outbreak. Over time, however, deep sampling of the nasopharynx is necessary to maximize detection of subclinical infections. Uncertainty in detection using PCR on nasal swab samples can complicate herd assessments and limit the ability to fully assess risk. This study emphasizes the difficulty of identifying chronic carriers following an outbreak and underscores the need for further research to inform M. bovis management and minimize risk in the sensitive and iconic American bison.
Information on pathogens, including zoonotic agents, in European brown hares (Lepus europaeus) in the Netherlands is lacking. In this paper, we provide an overview of the most common pathogens found in hares in the Nethe...Information on pathogens, including zoonotic agents, in European brown hares (Lepus europaeus) in the Netherlands is lacking. In this paper, we provide an overview of the most common pathogens found in hares in the Netherlands. Specifically, we assessed whether land use and climatic factors influence the occurrence of a frequently detected pathogen in hares, that is, Yersinia spp., and determined whether there are changes in the occurrence of pathogens in hares between the periods 1966-77 and 2009-21. Postmortem examinations were available for 513 hares from 2009 to 2021 and for 757 hares from 1966 to 1977. Descriptive analysis was performed on these data, assessing hare metadata, pathology, reasons for submission, land use surrounding the location of recovery, and seasonality. A logistic mixed modeling approach was used to identify predictors for the presence of Yersinia spp. In both periods, hares were identified as competent hosts for several pathogens, including zoonotic agents. Yersinia spp. was the most frequently identified pathogen (recent period, 12.1%; historic period, 25.1%). Between 2009 and 2021, Yersinia spp. presence was positively associated with the proportion of agricultural land use and negatively associated with the mean daily minimum temperature. The results presented herein provide a better understanding of pathogens circulating in free-ranging hares in the Netherlands and are relevant to hare health and public health and for wildlife managers and future surveillance strategies. Furthermore, the results emphasize the inherent difficulties associated with retrospective analyses of these types of data.
Yellow-eyed Penguins (Megadyptes antipodes; hoiho) are a unique, nationally endangered, and declining species endemic to New Zealand. Between 28 April 2023 and 28 February 2024, histopathologic examination found that six...Yellow-eyed Penguins (Megadyptes antipodes; hoiho) are a unique, nationally endangered, and declining species endemic to New Zealand. Between 28 April 2023 and 28 February 2024, histopathologic examination found that six Yellow-eyed Penguins died from septicemia. A Pasteurella sp. was cultured from all six cases and confirmed as Pasteurella multocida in three cases by either MALDI-TOF (n=2) or genome sequencing (n=1). One isolate was confirmed as P. multocida type A:L3 by molecular techniques and genome sequencing. Pasteurella multocida is the causative agent of avian cholera; thus, finding P. multocida confirmed avian cholera as the cause of these deaths. A source for the bacterial infections could not be identified in these cases. Although avian cholera has been previously reported in other penguin species, to our knowledge, these are the first reported cases of P. multocida in Yellow-eyed Penguins. Yellow-eyed Penguins do not nest in dense colonies, and direct contact between birds outside of breeding pairs is irregular, making this case series an unusual presentation for avian cholera. The loss of six individuals, including three of breeding age, will have a significant impact on the mainland Yellow-eyed Penguin population, and the potential for further losses to avian cholera cannot be discounted. This case series illustrates the benefits of multiagency collaboration in monitoring for, and investigation of, potentially new and emerging diseases in threatened species.
Neospora caninum is an obligate intracellular protozoan parasite that causes hind-limb paralysis in dogs and abortions in cattle. Recurrent storms of abortions in cattle in Australia are estimated to cause an economic lo...Neospora caninum is an obligate intracellular protozoan parasite that causes hind-limb paralysis in dogs and abortions in cattle. Recurrent storms of abortions in cattle in Australia are estimated to cause an economic loss of AU$100 million each year, but the source of infection in cattle (i.e., via wild or domestic definitive hosts) remains to be established. We aimed to determine potential sources of horizontal transmission of N. caninum after recent evidence that wild dogs (Canis familiaris) shed N. caninum oocysts in Victoria, Australia. To determine infection levels among wild dogs, samples were collected from three sites in Victoria (n=52) in areas of high wild dog population density (Mansfield, Swifts Creek, and Tallangatta), and N. caninum detection was determined by PCR analysis of blood and duodenal samples. Based on the PCR assay of combined duodenal samples (flotation of duodenal content and just duodenal content), this study detected N. caninum in the fecal material of 11% of wild dogs in Mansfield and 21% of wild dogs in Swifts Creek. This study provides further insight into the possible role of wild dogs as a reservoir of N. caninum in Victoria.
Ticks transmit a variety of pathogens that affect both animal and human health, underscoring the importance of understanding diversity and transmission dynamics. The European hedgehog (Erinaceus europaeus) serves as a ho...Ticks transmit a variety of pathogens that affect both animal and human health, underscoring the importance of understanding diversity and transmission dynamics. The European hedgehog (Erinaceus europaeus) serves as a host for ticks such as Ixodes hexagonus and Ixodes ricinus, potentially playing a role in the enzootic cycle of tick-borne diseases. This study aimed to evaluate the use of hedgehogs as sentinels for monitoring tick-borne pathogens in urban and suburban areas. A total of 251 hedgehogs were involved in the study, conducted between 2019 and 2021, with 144 examined for ticks and 110 undergoing ear biopsies. Using real-time PCR, multiple pathogens were identified among the hedgehogs, including Borrelia afzelii, Rickettsia asembonensis, and Anaplasma phagocytophilum. Most (96%) ticks collected were I. hexagonus, primarily nymphs and adult females, confirming this species as the main infester of hedgehogs. Carcasses obtained from a wildlife animal hospital provided an accessible source of biological material for this study. The results indicated that hedgehogs could serve as sentinel hosts for the surveillance of Borrelia burgdorferi complex, Rickettsia spp., and A. phagocytophilum in urban and suburban environments. Further research is needed to explore the relationship among hedgehog population densities, tick infestation levels, and the prevalence of tick-borne pathogens. Such studies are essential to determine the contribution of hedgehogs to the enzootic transmission cycle of these pathogens and to evaluate the resultant risks to human health.
We report highly pathogenic avian influenza H5 virus infection in 10 Northern Fulmars (Fulmarus glacialis) found dead throughout January and February 2024 in the Netherlands. Five birds were infected with the H5N5 subtyp...We report highly pathogenic avian influenza H5 virus infection in 10 Northern Fulmars (Fulmarus glacialis) found dead throughout January and February 2024 in the Netherlands. Five birds were infected with the H5N5 subtype, notable for markers of adaptation to mammals. Continuous infectious disease surveillance remains important in wild birds.
Serologic assays are important tools for detecting the presence of antibodies that are indicative of past and ongoing infections. For wildlife, species-specific conjugates, which are used as detection antibodies in prima...Serologic assays are important tools for detecting the presence of antibodies that are indicative of past and ongoing infections. For wildlife, species-specific conjugates, which are used as detection antibodies in primary binding assays, are not available for most species. In these cases, conjugates for closely related species or immunoglobulin-binding proteins are frequently used. These are often not validated and their low functional affinity may result in false-negative results. We tested 11 commercial conjugates, including protein G and species- or family-specific secondary conjugated antibodies, on eight rodent and two insectivore species (shrews). Using direct ELISAs, between-species and within-species differences in the functional affinity of the conjugates were assessed. Large differences in antibody binding of the conjugates were observed. Some conjugates were species-specific, binding only to antibodies from one species, whereas others were able to bind across a broad range of species. The strength of the antibody-conjugate interaction varied between species and sometimes within species. In general, stronger antibody-conjugate interactions were observed for rodent species than for shrews. Our study underlines the importance of confirming species-specific functional affinity of a conjugate, even if the conjugate is known to bind to antibodies of a closely related species.
Between November 2021 and January 2023, the eyes of either slaughtered or deceased male American bison (Bison bison) and European bison (Bison bonasus) from Romania were investigated for the presence of Thelazia spp. nem...Between November 2021 and January 2023, the eyes of either slaughtered or deceased male American bison (Bison bison) and European bison (Bison bonasus) from Romania were investigated for the presence of Thelazia spp. nematodes (eye worms). These included seven farmed American bison from two locations and two wild European bison from reintroduction sites. Thelazia rhodesi and Thelazia skrjabini were present in three American bison and both European bison. A total of 38 nematodes were recovered, with T. rhodesi being the predominant species. Molecular analysis confirmed these findings and identified unique sequences for both species. The nematodes in American bison were distributed across the Pannonian and Continental biogeoregions, and those in European bison originated from the Alpine region. Thelazia spp. have not previously been reported in American bison, nor in European bison from Romania. The findings underscore the need for continuous monitoring and management of Thelazia infections to support conservation and reintroduction efforts. Future research should focus on the ecological factors influencing these infections and develop strategies to mitigate their impact on wildlife health.
Numerous marine mammal populations worldwide are declining because of increased anthropogenic and natural threats, including infectious disease. Brucella ceti, morbillivirus, and herpesvirus have been detected from stran...Numerous marine mammal populations worldwide are declining because of increased anthropogenic and natural threats, including infectious disease. Brucella ceti, morbillivirus, and herpesvirus have been detected from stranded cetaceans and been recognized as pathogens that may result in considerable cetacean morbidity and mortality. Beaked whale circovirus has been reported in multiple cetacean species in Hawaii, USA, and the western Pacific Ocean, but the pathologic relevance in these species remains uncertain. We screened for the presence of Brucella in 66 cetaceans of 17 species that stranded in Hawaii 2000-24 by targeting the insertion sequence 711 partial sequence using PCR. All Brucella-positive individuals were PCR tested for herpesvirus, morbillivirus, and circovirus coinfections. Of 66 individuals across eight species, 21 (31.8%) were positive for Brucella; 10/10 (100%) striped dolphins (Stenella coeruleoalba) and 5/6 (83.3%) pygmy killer whales (Feresa attenuata) tested were positive. Tissue positivity was highest in brain and lung tissue, with corresponding meningitis, hydrocephalus, and bronchopneumonia. We detected Brucella positivity across seven species; 7/10 (70%) of the positive subadults were striped dolphins. A single humpback whale (Megaptera novaeangliae) fetus was positive; the mother had died during dystocia. Viral coinfections were detected in 6/21 (33.3%) positive cases; circovirus was the most common coinfection, followed by morbillivirus and herpesvirus. Brucella ceti infection caused fatal disease in cetaceans in Hawaii, with a high percentage of strandings due to neurobrucellosis in striped dolphins.
Using molecular testing and serology, we investigated Reunion Harrier (Circus maillardi) exposure to avian influenza virus, West Nile virus, and infectious bronchitis virus. We detected influenza virus antibodies in 2 of...Using molecular testing and serology, we investigated Reunion Harrier (Circus maillardi) exposure to avian influenza virus, West Nile virus, and infectious bronchitis virus. We detected influenza virus antibodies in 2 of 73 birds and hypothesized that infection might occur by consumption of poultry.
Mannheimia granulomatis-associated lesions have been poorly described compared with those associated with other members of the Pasteurellaceae family; they include pneumonia, panniculitis, and keratoconjunctivitis in dom...Mannheimia granulomatis-associated lesions have been poorly described compared with those associated with other members of the Pasteurellaceae family; they include pneumonia, panniculitis, and keratoconjunctivitis in domestic and wild ruminants and hares. We describe 15 cases of roe deer (Capreolus capreolus) showing M. granulomatis-infected oral lesions that were detected in France between 2016 and 2023. Comprehensive necropsies were performed, with additional analyses based on findings. All deer were >15 mo of age on the basis of tooth eruption. They were thin (1/15), cachectic (13/15), or of unknown body condition (1/15). They exhibited multiple cryptic millimetric to centimetric caseous granulomas within the lips, tongue, or cheeks (13/15); pyogranulomatous lymphadenitis of a mandibular lymph node (1/15); or necrosuppurative mandibular osteomyelitis with bone proliferation (1/15). Histopathologically, oral lesions of 10/15 animals showed multifocal, severe, chronic pyogranulomatous cheilitis, glossitis, or stomatitis with intralesional Gram-negative bacterial colonies lined by Splendore-Hoeppli material. Amyloidosis was detected in 4/11 animals for which tissues were submitted for microscopic examination, affecting the abomasum, the spleen, and a minor salivary gland in, respectively, 4/6, 3/5, and 1/8 animals for which the relevant organs were assessed histologically. Amyloid deposits showed strong immunoreactivity with a murine monoclonal antibody directed against amyloid AA. AA amyloidosis, never previously described in roe deer, was considered secondary to chronic inflammation. Mannheimia granulomatis was cultured and identified biochemically or by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in oral lesions of all individuals. Coinfection with other bacterial species was sporadically identified. We considered the chronic emaciation and death of these animals to be multifactorial, involving oral lesions, secondary amyloidosis when present, parasitic infestation of variable severity, and probably environmental factors. Further investigation is needed to understand the epidemiology and pathogenesis of M. granulomatis infection in roe deer, including a possible propensity to emerge as temporal and geographic clusters and to induce AA amyloidosis.
Birds are frequently stressed by their exposure to parasites and pathogens. The heterophil to lymphocyte (H:L) ratio has been proposed as a measure of physiological stress. This study investigates the prevalence of the b...Birds are frequently stressed by their exposure to parasites and pathogens. The heterophil to lymphocyte (H:L) ratio has been proposed as a measure of physiological stress. This study investigates the prevalence of the bacterial pathogen Mycoplasma gallisepticum and Haemosporidia in Mexican House Finches (Haemorhous mexicanus). To test the extent to which pathogens stress their hosts we compared total and differential leucocyte counts in four groups of birds with different infection statuses: birds co-infected with M. gallisepticum and haemosporidia, birds infected with either M. gallisepticum or haemosporidia, and birds infected with neither. We hypothesized that co-infected birds would exhibit higher physiological stress, reflected in leukocyte parameters, plus, based on previous experiments, that both M. gallisepticum and haemosporidia would benefit from the presence of each other. We found that 73.6% of House Finches were infected with M. gallisepticum, and 43.1% with haemosporida. Both pathogens had a higher load in co-infected birds. Higher H:L ratios were found in co-infected birds compared to birds with a single infection. The study highlights the complexity of immune responses under co-infection. Our results contribute to the understanding of host-pathogen interactions and stress physiology in wild birds, highlighting the importance of hematological parameters as indicators of stress and providing insights into the ecological impacts of pathogen infections in avian populations. This emphasizes the significance of studying leukocyte profiles in the wild.
Taylor JT, Lee V, Dearlove T
… +11 more, Jolly M, Wierenga JR, Dubrulle J, Hodgkinson-Bean J, Hunter S, Gartrell B, Morgan K, McInnes K, French N, Holmes EC, Geoghegan JL
Sporadic cases of dermatosis have been reported in wild Ōkārito Rowi (Apteryx rowi), a species of brown kiwi, for over a decade. The disease exhibits distinctive features, including lesions, lichenification, and feather...Sporadic cases of dermatosis have been reported in wild Ōkārito Rowi (Apteryx rowi), a species of brown kiwi, for over a decade. The disease exhibits distinctive features, including lesions, lichenification, and feather loss. Swab samples and full-thickness skin biopsies were collected during a survey of affected kiwi in 2023 for a metatranscriptome-based, total infectome investigation to identify any possible microbial agents associated with the disease. Our approach identified novel viruses as well as a species of nematode in high relative abundance. We found a highly abundant hepacivirus within the Flaviviridae, but only in some mild cases of dermatitis across all sample types, and in both active and chronic infections. In addition, we found a significant shift in the taxonomic composition of the nonviral microbiome within severe chronic dermatitis cases, particularly an increased abundance of transcripts from a Eucoleus sp. parasitic. Although determining the primary cause of disease in critically endangered wildlife such as Rowi remains challenging, our detection of novel and highly abundant microorganisms opens new lines of inquiry to investigate their potential association with dermatosis in this nationally iconic species.
In the Canadian North, trichinellosis is a zoonotic disease that is primarily transmitted by the consumption of improperly cooked walrus (Odobenus rosmarus) and bear (Ursus spp.) meat. Trichinella spp. infections in othe...In the Canadian North, trichinellosis is a zoonotic disease that is primarily transmitted by the consumption of improperly cooked walrus (Odobenus rosmarus) and bear (Ursus spp.) meat. Trichinella spp. infections in other wildlife provide information about where transmission occurs, the species present, and the potential risk of transmission to humans. Wolverines (Gulo gulo) can serve as a sentinel species, due to their scavenging behavior, high trophic level, and high larval burden when infected. We determined the prevalence, intensity, and genetic diversity of Trichinella infections in wolverines in Churchill, Manitoba, Canada, and compared these results with those of studies conducted in other northern Canadian provinces. Larvae were found in 41% (9/22) of hosts, with a mean intensity of 5.93 larvae per gram of tongue tissue. The DNA sequencing of the cytochrome b gene confirmed that all hosts were infected with Trichinella nativa and that diversity was limited with only two distinct haplotypes recovered. The presence of T. nativa in wolverines indicates that this parasite is being maintained in a sylvatic cycle and that humans could be at risk of transmission in northern Manitoba.
Bog turtles (Glyptemys muhlenbergii) are critically endangered semiaquatic turtles inhabiting fens and bogs along the east coast of the USA. Threats to their survival include habitat loss from development, roads, altered...Bog turtles (Glyptemys muhlenbergii) are critically endangered semiaquatic turtles inhabiting fens and bogs along the east coast of the USA. Threats to their survival include habitat loss from development, roads, altered hydrology, ecological succession, proliferation of invasive plants, poaching, and infectious disease. In response to an increase in bog turtle mortality and concerns about their health, we assessed bog turtle health and pathogen prevalence across five USA states-New York, Pennsylvania, New Jersey, Delaware, and Maryland-between 2014 and 2022. Adenoviruses, specifically barthadenovirus, or atadenoviruses, siadenoviruses, and testadenoviruses, have been associated with infection and disease in chelonians. To determine whether adenoviruses were present in free-ranging bog turtle populations, we tested archived choanal-cloacal swabs by PCR. Overall, 26 (49%) of 53 pooled samples collected between 2014 and 2018 and 9 (30%) of 30 samples collected in 2022 were positive for adenovirus. The DNA sequence and phylogenetic analyses revealed at least four distinct and novel lineages: Glyptemys adenovirus 1 (a testadenovirus first detected in Delaware and New Jersey in 2014 and in New York and Pennsylvania in 2016), Glyptemys adenovirus 2 (a testadenovirus detected in New Jersey and Pennsylvania in 2014), Glyptemys adenovirus 3 (an unclassified adenovirus detected in New Jersey in 2016), and Glyptemys adenovirus 4 (a siadenovirus detected in Maryland in 2016). None of these adenoviruses were associated with clinical signs or disease; however, knowledge of which pathogenic organisms are circulating in the bog turtle populations can inform decisions on monitoring, species recovery efforts, and captive breeding programs.
Galapagos giant tortoises are the largest terrestrial vertebrates and one of the most iconic species of the Galapagos islands. Their populations continue to be endangered because of multiple factors, mostly driven by ant...Galapagos giant tortoises are the largest terrestrial vertebrates and one of the most iconic species of the Galapagos islands. Their populations continue to be endangered because of multiple factors, mostly driven by anthropogenic activities. In recent years, the presence of novel infectious agents of potential conservation concern, including two adenoviruses and two herpesviruses, has been reported in some Galapagos tortoise species. With the aim of describing the presence and prevalence of these pathogens in additional tortoise species, we collected oral, ocular, and cloacal swabs from 99 free-living tortoises from San Cristobal (Chelonoidis chathamensis) and Isabela islands (Chelonoidis vicina and Chelonoidis guntheri) and screened these for the presence of herpesvirus and adenovirus by PCR. We detected Chelonoidis adenovirus 1 (CheAdV1) and Chelonoidis adenovirus 2 (CheAdV2) in all sampling locations, whereas we did not detect herpesvirus in any tortoises. Phylogenetic analyses revealed that San Cristobal nucleotide and amino acid sequences clustered in a clade with CheAdV1, whereas the Isabela nucleotide and amino acid sequences clustered together with CheAdV2. This contributes additional information regarding tortoise viral distribution in the Galapagos Archipelago. We recommend long-term health surveillance of tortoises and other wildlife species to inform conservation actions in the Galapagos involving captive-breeding and rewilding programs.
Fungal pathogens of reptiles are commonly diagnosed, with Aphanoascella galapagosensis known to affect Galapagos giant tortoises (Chelonoidis spp.), although the implications of this fungus for the health and well-being...Fungal pathogens of reptiles are commonly diagnosed, with Aphanoascella galapagosensis known to affect Galapagos giant tortoises (Chelonoidis spp.), although the implications of this fungus for the health and well-being of these unique species remain understudied. Therefore, the goal of this study was to explore health and environmental variables that may be correlated with white lesion shell coverage associated with A. galapagosensis in free-living Galapagos tortoises. For 200 western Santa Cruz tortoises (Chelonoidis porteri) and 70 Alcedo tortoises (Chelonoidis vandenburghi), the percentage of white lesion fungal coverage was calculated based on images taken from six different projections per individual, including the carapace and plastron. White lesion shell coverage was compared between species and correlated with hematology and blood chemistry parameters, season, elevation, shell integrity (i.e., scratches, lesions, and fractures), and land-use type. A higher percentage of white lesion carapacial fungal coverage was found in western Santa Cruz tortoises (3.3%) than Alcedo tortoises (0.055%). In both species, a positive correlation was found between white lesion fungal coverage and lymphocyte counts. In addition, tortoises sampled in more humid areas had a higher prevalence of fungal coverage. This study indicates that fungal coverage may be influenced by environmental factors and may affect the overall health status of critically endangered Galapagos giant tortoises.
Trematodes in the genus Clinostomum develop into large metacercariae that can sometimes achieve high intensity in their second intermediate hosts, potentially causing pathology. In 2022, there was 100% (15/15) infection...Trematodes in the genus Clinostomum develop into large metacercariae that can sometimes achieve high intensity in their second intermediate hosts, potentially causing pathology. In 2022, there was 100% (15/15) infection prevalence of Clinostomum marginatum, with a mean of 3,125 metacercariae per salamander (range: 279-4,075) and a median of 2,949. Dissection and histopathology results indicated that C. marginatum was found in nearly all body tissues and organs of the salamanders. Parasitic infection was closely associated with chronic inflammation and fibrosis around the cysts, with heavily infected hosts exhibiting altered buoyancy and difficulty swimming. The following summer, only 22.0% (6/27) of salamanders were infected with C. marginatum; based on their size, these were probably overwintering larvae from 2022. Here, we characterize a morbidity event in tiger salamanders (Ambystoma tigrinum) from a freshwater pond in Boulder, Colorado, USA, linked to extreme clinostomid infection. After using necropsy, genomic analysis, and histopathological assessment to record the intensity and pathology associated with infections, we assessed the validity of using noninvasive, image-based methods to quantify infection. Over 2 yr, we recorded in situ video imagery of 62 larval A. tigrinum, of which a subset of larvae was collected for parasitological assessment. Infection loads of C. marginatum quantified indirectly via imagery of subcutaneous cysts correlated strongly with direct counts via necropsy and were consistent between independent reviewers, highlighting the utility of this non-invasive assessment method. All evaluated A. tigrinum were co-infected with additional parasite taxa. Prevalence of other trematodes included Ribeiroia ondatrae (80%) and Cephalogonimus americanus (77.5%), as well as the nematode Megalobatrachonema elongata (75%). To discern the impact of such high metacercarial burden of C. marginatum on tiger salamander, future work should incorporate experimental approaches to evaluate load-dependent consequences for host growth, survival, behavior, and time to metamorphosis.