Allan Pessier

Washington State University | WSU · Department of Veterinary Microbiology & Pathology (VMP)

Batrachochytrium salamandrivorans (Bsal) is a fungal pathogen of amphibians that is emerging in Europe and could be introduced to North America through international trade or other pathways. To evaluate the risk of Bsal invasion to amphibian biodiversity, we performed dose-response experiments on 35 North American species from 10 families, includin...

Emerging infectious diseases are among the leading drivers of the sixth mass extinction. The recent invasion of a highly pathogenic chytrid fungus, Batrachochytrium salamandrivorans (Bsal), across Europe has led to salamander mass mortality. To date, it remains unclear whether Bsal will cause salamander mass mortalities in North America. Here, we t...

A correction to this paper has been published: https://doi.org/10.1007/s10530-021-02578-5

Necropsy is an essential diagnostic in fish medicine. Specimens should be fresh; this means that euthanized specimens typically provide more information than fish that were found dead. Potential ancillary diagnostics, such as cultures and PCR, should be determined prior to starting a necropsy. Wet mounts examined under direct microscopy and impress...

Recent reports have highlighted a lower-than-expected prevalence of neoplasia in elephants and suggested mechanisms for cancer resistance. But despite infrequent reports in the literature, uterine neoplasia is common in managed Asian elephants (Elephas maximus). This study is an archival review of reproductive tract neoplasia in 80 adult female Asi...

Over the past 30 years, the California condor (Gymnogyps californianus) population has rebounded from 22 individuals to over 200 birds living in the wild. Historical impacts to the population have been largely anthropogenic. In this study, we explore mortality and cause of death data from condors that died during the years 2010-2014 and compare the...

The number of amphibian reintroductions and other conservation translocations has increased in recent decades. Clearer guidance to plan, implement, and obtain resources for amphibian reintroductions is needed to improve conservation outcomes. The vast diversity within Class Amphibia, which contains 8000+ species, makes generalisations difficult, bu...

Effectively planning conservation introductions involves assessing the suitability of both donor and recipient populations, including the landscape of disease risk. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has caused extensive amphibian declines globally and may hamper reintroduction attempts. To determin...

The vertebrate class Amphibia is a diverse group of animals that includes frogs, salamanders, and the lesser‐known caecilians. Evaluation of the integumentary system is especially important in amphibians because of the unique physiologic role of the skin in water absorption, osmoregulation, and respiration. Common clinical samples include skin scra...

Cancer is a common diagnosis in many mammalian species, yet they vary in their vulnerability to cancer. The factors driving this variation are unknown, but life history theory offers potential explanations to why cancer defense mechanisms are not equal across species. Here we report the prevalence of neoplasia and malignancy in 37 mammalian species...

A group of five juvenile Meller's chameleons (Trioceros melleri) experienced 100% mortality over a period of 1 mo due to ranavirus infection. The index case was found dead without premonitory signs. The three subsequent cases presented with nonspecific clinical signs (lethargy, decreased appetite, ocular discharge) and were ultimately euthanatized....

American bullfrogs Lithobates catesbeianus are thought to be important in the global spread of ranaviruses-often lethal viruses of cold-blooded vertebrates-because they are commonly farmed, dominate international trade, and may be 'carriers' of ranavirus infections. However, whether American bullfrogs are easily infected and maintain long-lasting r...

A 12‐year‐old female African Clawed Frog (Xenopus laevis) displayed lethargy and anorexia for 1 week. Radiographs detected a moderately reduced volume of aerated lung with lobulated margins with the left lung predominantly affected. Transcelomic ultrasound revealed marked consolidation of the left lung. Postmortem examination confirmed suppurative...

These are the Abstracts of the 2019 annual meeting of SNVB, WA TWS, and NW PARC. I have two abstracts in this compilation: Olson et al., Density Management and Riparian Buffer Study update, pp 154-155; Weil and Olson, NW PARC update, pp 162-163.

Aetokthonos hydrillicola (Ah) is a newly described cyanobacteria that forms dense colonies on aquatic macrophytes, primarily invasive Hydrilla verticillata, and is associated with mortality of freshwater wildlife. Prior research shows that Ah growing on Hydrilla is potently toxic to waterbirds, turtles, and fish, suggesting potentially broad sensit...

Amphibian skin is highly variable in structure and function across anurans,and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis (Bd), but interspecific variation in sloughing frequency is...

Spindly Leg Syndrome (SLS) is a persistent animal welfare issue associated with the rearing of amphibians in captivity. We conducted two experiments to investigate the effects of diet, water composition and overfeeding on prevalence of SLS in newly metamorphosed harlequin frogs (Atelopus spp.). In our first experiment, we offered 400 full-sibling t...

Periphyton collection from historical Atelopus habitat. Details of attempted collection and nutritional analysis of diatoms and algae growing in Atelopus habitat. (DOCX)

Experimental data (excel file). Tab 1: Raw results data from experiment 1. Tab 2: Raw results data from experiment 2. (XLSX)

Brand information. Account of brands, makes and models used in this experiment. (DOCX)

Background: Tuberculosis is widely known as a progressive disease that affects endothermic animals, leading to death and/or economical losses, while mycobacterial infections in amphibians are commonly due to nontuberculous mycobacteria. To the authors' knowledge, this report describes the first case of bovine tuberculosis in a poikilothermic anima...

Amphibian populations are in decline worldwide as they face a barrage of challenges, including infectious diseases caused by ranaviruses and the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). Here we describe seasonal dynamics of Bd and ranavirus detection in free-ranging post-metamorphic wood frogs Lithobates sylvaticus, boreal chor...

As extinctions continue across the globe, conservation biologists are turning to species reintroduction programs as one optimistic tool for addressing the biodiversity crisis. For repatriation to become a viable strategy, fundamental prerequisites include determining the causes of declines and assessing whether the causes persist in the environment...

An adult male African tiger snake (Telescopus semiannulatus) was diagnosed with disseminated mycobacteriosis and a hepatic biliary cystadenocarcinoma. Histologically, the spleen was largely replaced by extracellular deposits of eosinophilic, fibrillar to hyaline material. Similar material was also present in the testicular interstitium and occasion...

Freshwater biodiversity is imperiled across the globe, and multiple stressors such as habitat alteration, non-native species invasion, disease, and climate change can act in concert to threaten vulnerable taxa. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis, is one of the causative factor...

Recurrent eosinophilic granuloma (EG) in two captive eastern black rhinoceros (Diceros bicornis michaeli) was effectively managed with glucocorticoids and antihistamines. The first case was a female and the second case was a male. The animals were housed at separate institutions and initially presented with hemorrhagic oral lesions. Multifocal lesi...

To the Editor The study by Dr Abegglen and colleagues affirmed the Peto paradox and suggested that elephants are cancer resistant by virtue of multiple TP53 gene copies and enhanced responses to DNA damage.1 This study epitomizes a “One Health” approach to solving important disease problems shared by humans and animals.2 However, from our experienc...

A 7-yr-old male captive American bullfrog ( Lithobates catesbeianus ) presented with a 2-wk history of an enlarged, ulcerated nuptial pad on the mediopalmar surface of the first digit of the left carpus. A 3-mm wedge biopsy of the mass was not diagnostic and differentials included an epidermal inclusion cyst or squamous cell carcinoma. No fungal or...

We performed a rapid response investigation to evaluate the presence and distribution of amphibian pathogens in Madagascar following our identification of amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) and ranavirus in commercially exported amphibians. This targeted risk-based field surveillance program was conducted from February to...

The pathogenic fungus Batrachochytrium dendrobatidis (Bd) is a major conservation concern because of its role in decimating amphibian populations worldwide. We used quantitative PCR to screen 244 museum specimens from the Korean Peninsula, collected between 1911 and 2004, for the presence of Bd to gain insight into its history in Asia. Three specim...

Recognizing the pathological changes caused by ranaviruses, understanding how to properly collect test samples, and knowing what diagnostic tools to choose are key to detecting ranaviruses and in determining whether they are a factor in morbidity and mortality events. Whether infection occurs in fish, reptiles, or amphibians, clinical disease is ty...

The polar bear (Ursus maritimus), with its wide-ranging movements, solitary existence and seasonal reproduction, is expected to favor chemosignaling over other communication modalities. However, the topography of its Arctic sea ice habitat is generally lacking in stationary vertical substrates routinely used for targeted scent marking in other bear...

Vitamin A deficiency is a recently recognized nutritional disease in amphibians fed insect-based diets. The classic pathologic lesion that has been associated with hypovitaminosis A in amphibians is squamous metaplasia of the lingual and oral mucosa. In an attempt to further characterize the range of lesions that may be associated with vitamin A de...

The Epidemiology Working Group, a subgroup of the participants of the Disney's Animal Kingdom Workshop on "Ex situ Amphibian Medicine and Nutrition," identified a critical need to design and implement approaches that will facilitate the assessment and evaluation of factors impacting amphibian health. In this manuscript, we describe and summarize th...

A captive 'survival assurance' population of 56 endangered boreal toads Anaxyrus boreas boreas, housed within a cosmopolitan collection of amphibians originating from Southeast Asia and other locations, experienced high mortality (91%) in April to July 2010. Histological examination demonstrated lesions consistent with ranaviral disease, including...

The success of ex situ survival assurance populations as tools for amphibian conservation depends on the health and reproductive success of founder populations. Necropsy examination and histopathology of animals that die in assurance populations are useful for the identification of population-limiting disease problems and can help to direct applied...

We analyzed museum specimens from two regions of Guatemala for the presence of the pathogenic amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) using both histological and PCR-based assays. We determined that the pathogen was present at one site at low prevalence in 1980 and 1981, immediately preceding drastic declines of amphibian in th...

A 42-year-old female Indian elephant (Elephas maximus indicus) developed a sudden onset of excessive salivation and dysphagia. Esophageal obstruction was suspected; possibly related to palm frond ingestion. Esophageal endoscopy revealed a mat of plant material in the distal esophagus. An initial attempt at relieving the obstruction was unsuccessful...

The emerging infectious amphibian diseases caused by amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) and ranaviruses are responsible for global amphibian population declines and extinctions. Although likely to have been spread by a variety of activities, transcontinental dispersal appears closely associated with the international trad...

abstract : To fully understand the impacts of the chytrid fungus Batrachochytrium dendrobatidis (Bd) on amphibians it is necessary to examine the interactions between populations and their environment. Ecologic variables can exacerbate or ameliorate Bd prevalence and infection intensity, factors that are positively related when Bd is acting on naiv...

Chytridiomycosis, caused by the chytridiomycete fungus, Batrachochytrium dendrobatidis, is an important pathogen of amphibians in captivity and is a major concern for global conservation of amphibians. The organism infects keratinized epithelial cells of amphibian skin and causes disease and mortality by interfering with important skin functions, e...

A multispecies amphibian larval mortality event, primarily affecting American bullfrogs Lithobates catesbeianus, was investigated during April 2011 at the Mike Roess Gold Head Branch State Park, Clay County, Florida, USA. Freshly dead and moribund tadpoles had hemorrhagic lesions around the vent and on the ventral body surface, with some exhibiting...

All anuran specimens in the Wildlife Conservation Society's collections testing positive for Batrachochytrium dendrobatidis (Bd) were treated with itraconazole and then studied after treatment to assess the long-term effects of itraconazole and the drug's effectiveness in eliminating Bd carriers. Twenty-four individuals and eight colonies of 11 dif...

Since 1999, infections with an incompletely characterized alveolate protozoan variously reported as a Dermocystidium-like organism, a Perkinsus-like agent, and Dermomycoides sp. have been associated with mortality events in tadpoles of ranid frogs from the USA. However, disease or mortality events due to this organism have not been described in pos...

Due in large part to recent global declines and extinctions, amphibians are the most threatened vertebrate group. Captive assurance colonies may be the only lifeline for some rapidly disappearing species. Maintaining these colonies free of disease represents a challenge to effective amphibian conservation. The fungal disease chytridiomycosis, cause...

Effective treatment methods to eliminate infection with Batrachochytrium dendrobatidis (Bd) are required for development of sustainable captive survival assurance populations of amphibians and to reduce the risk of introducing Bd to new locations as part of amphibian trade or reintroduction programs. Treatment with itraconazole baths at 100 mg l-1...

Chytridiomycosis, a disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is driving amphibian declines and extinctions in protected areas globally. The introduction of invasive reservoir species has been implicated in the spread of Bd but does not explain the appearance of the pathogen in remote protected areas. In the high el...

Rhabdoviruses infect a variety of hosts, including non-avian reptiles. Consensus PCR techniques were used to obtain partial RNA-dependent RNA polymerase gene sequence from five rhabdoviruses of South American lizards; Marco, Chaco, Timbo, Sena Madureira, and a rhabdovirus from a caiman lizard (Dracaena guianensis). The caiman lizard rhabdovirus for...

We document causes of death in free-ranging California Condors (Gymnogyps californianus) from the inception of the reintroduction program in 1992 through December 2009 to identify current and historic mortality factors that might interfere with establishment of self-sustaining populations in the wild. A total of 135 deaths occurred from October 199...

Batrachochytrium dendrobatidis is a fungal pathogen responsible for a potentially fatal disease of amphibians. We conducted a survey for B. dendrobatidis in the Appalachian Mountains of southwestern North Carolina, USA, from 10 June to 23 July 23 2009. Ventral skin swabs were collected from plethodontid salamanders (n=278) and real-time PCR was per...

To fully comprehend chytridiomycosis, the amphibian disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), it is essential to understand how Bd affects amphibians throughout their remarkable range of life histories. Crawfish Frogs (Lithobates areolatus) are a typical North American pond-breeding species that forms explosive sprin...

ABSTRACT An emerging disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis has been associated with morbidity, mortality, and extinction of species. Typically, researchers have detected B. dendrobatidis only when examining amphibians for causes of mortalities; few data exist on infection rates where mortalities are lacki...

Effective and safe treatments of amphibian chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), are needed to prevent mortality in captive programs, reduce the risk of disease spread, and better manage the disease in threatened wild populations. Bd is susceptible to a range of antifungal agents and low levels of heat (>30 degrees C) whe...

Contemporary global declines and mortality events in amphibian populations have been often attributed to infectious disease and climate change, separately and in combination. We report on an enigmatic mortality event in the only known population of the Critically Endangered frog species Xenopus longipes. This aquatic and biologically distinctive sp...

Lead poisoning is a primary factor impeding the survival and recovery of the critically endangered California Condor (Gymnogyps californianus). However, the frequency and magnitude of lead exposure in condors is not well-known in part because most blood lead monitoring occurs biannually, and biannual blood samples capture only 10% of a bird’s annua...

A fatal outbreak of amphibian chytridiomycosis in a group of critically endangered Kihansi spray toads (Nectophrynoides asperginis) prompted institution-wide testing for Batrachochytrium dendrobatidis (Bd) infection in the amphibian collections of the Wildlife Conservation Society (WCS). Animal sampling was accomplished following established protoc...