Designing screening protocols for amphibian disease that account for imperfect and variable capture rates of individuals

The amphibian chytrid fungus, Batrachochytrium dendrobatidis, is one of the main factors in global amphibian decline. Accurate knowledge of its presence and prevalence in an area is needed to trigger conservation actions. However, imperfect capture rates determine the number of individuals caught and tested during field surveys, and contribute to the uncertainty surrounding estimates of prevalence. Screening programs should be planned with the objective of minimizing such uncertainty. We show how this can be achieved by using predictive models that incorporate information about population size and capture rates. Using as a case study an existing screening program for three populations of the yellow-bellied toad (Bombina variegata pachypus) in northern Italy, we sought to quantify the effect of seasonal variation in individual capture rates on the uncertainty surrounding estimates of chytrid prevalence. We obtained estimates of population size and capture rates from mark-recapture data, and found wide seasonal variation in the individual recapture rates. We then incorporated this information in a binomial model to predict the estimates of prevalence that would be obtained by sampling at different times in the season, assuming no infected individuals were found. Sampling during the period of maximum capture probability was predicted to decrease upper 95% credible intervals by a maximum of 36%, compared with least suitable periods, with greater gains when using uninformative priors. We evaluated model predictions by comparing them with the results of screening surveys in 2012. The observed results closely matched the predicted figures for all populations, suggesting that this method can be reliably used to maximize the sampling size of surveillance programs, thus improving their efficiency

No detection of chytrid in first systematic screening of Bombina variegata pachypus (Anura: Bombinatoridae) in Liguria, northern Italy

The Apennine Yellow-bellied toad Bombina variegata pachypus, a small anuran endemic to peninsular Italy, has been declining throughout its range over the last 30 years. Although mortality by chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, was first reported for the species in 2004, its role in the decline has not yet been assessed. Between 2011 and 2012 we sampled eight populations of B. v. pachypus in Liguria, northern Italy, swabbing 86 and 143 individuals respectively, corresponding to between 24 and 80% of the estimated individuals within each population. We did not detect chytrid in any the samples collected. For the three largest populations in the region, we can rule out infections of prevalence greater than 10% with at least 98% confidence. Research at a larger scale is urgently needed to clarify the role of B. dendrobatidis in the decline of this and other amphibians in Italy

Efficacy of chemical disinfectants for the containment of the salamander chytrid fungus Batrachochytrium salamandrivorans

The recently emerged chytrid fungus Batrachochytrium salamandrivorans (Bsal) causes European salamander declines. Proper hygiene protocols including disinfection procedures are crucial to prevent disease transmission. Here, the efficacy of chemical disinfectants in killing Bsal was evaluated. At all tested conditions, Biocidal (R), Chloramine-T (R), Dettol medical (R), Disolol (R), ethanol, F10 (R), Hibiscrub (R), potassium permanganate, Safe4 (R), sodium hypochlorite, and Virkon S (R), were effective at killing Bsal. Concentrations of 5% sodium chloride or lower, 0.01% peracetic acid and 0.001-1% copper sulphate were inactive against Bsal. None of the conditions tested for hydrogen peroxide affected Bsal viability, while it did kill Batrachochytrium dendrobatidis (Bd). For Bsal, enzymatic breakdown of hydrogen peroxide by catalases and specific morphological features (clustering of sporangia, development of new sporangia within the original sporangium), were identified as fungal factors altering susceptibility to several of the disinfectants tested. Based on the in vitro results we recommend 1% Virkon S (R), 4% sodium hypochlorite and 70% ethanol for disinfecting equipment in the field, lab or captive setting, with a minimal contact time of 5 minutes for 1% Virkon S (R) and 1 minute for the latter disinfectants. These conditions not only efficiently target Bsal, but also Bd and Ranavirus

Amphibian chytridiomycosis : a review with focus on fungus-host interactions

Amphibian declines and extinctions are emblematic for the current sixth mass extinction event. Infectious drivers of these declines include the recently emerged fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (Chytridiomycota). The skin disease caused by these fungi is named chytridiomycosis and affects the vital function of amphibian skin. Not all amphibians respond equally to infection and host responses might range from resistant, over tolerant to susceptible. The clinical outcome of infection is highly dependent on the amphibian host, the fungal virulence and environmental determinants. B. dendrobatidis infects the skin of a large range of anurans, urodeles and caecilians, whereas to date the host range of B. salamandrivorans seems limited to urodeles. So far, the epidemic of B. dendrobatidis is mainly limited to Australian, neotropical, South European and West American amphibians, while for B. salamandrivorans it is limited to European salamanders. Other striking differences between both fungi include gross pathology and thermal preferences. With this review we aim to provide the reader with a state-of-the art of host-pathogen interactions for both fungi, in which new data pertaining to the interaction of B. dendrobatidis and B. salamandrivorans with the host's skin are integrated. Furthermore, we pinpoint areas in which more detailed studies are necessary or which have not received the attention they merit

Prolonged environmental persistence requires efficient disinfection procedures to control Devriesea agamarum associated disease in lizards

Aims: Devriesea agamarum infection causes chronic proliferative dermatitis, especially in desert dwelling lizards. The present study was concerned with evaluating persistency of D. agamarum in the environment and the evaluation of the efficacy of various disinfection procedures. Methods and Results: First, the survival of D. agamarum was assessed both in dermal crusts obtained from clinically and naturally infected lizards, and during periods of prolonged nutrient starvation on dry surface, in moist sand and in distilled water. Secondly, a modified European Suspension Test was performed to determine the efficacy of eight procedures for the disinfection of equipment, environmental surfaces and the topical treatment of D. agamarum-associated dermal lesions. The bacterium proved to persist and remain viable for up to 57 days in dermal crusts and for more than 5 months in moist sand and distilled water. In contrast, survival on dry surfaces was limited. The results of the described dilution-neutralization method demonstrated that most of the tested disinfection procedures were sufficient in achieving a 5-decimal logarithmic reduction in the number of D. agamarum colony-forming units. The use of relatively low concentrations of hydrogen peroxide and a boric and peracetic acid solution on the other hand resulted in insufficient reduction in viable counts. Conclusions: Devriesea agamarum can persist for long periods of time in the environment, especially under moist conditions, making the use of suitable disinfection procedures necessary. Significance and Impact of the Study: This study demonstrates the need for a dry environment for most desert lizards and the use of effective disinfection procedures next to antimicrobial treatment to eliminate D. agamarum-associated disease from captive saurian collections

Detection of arenavirus in a peripheral odontogenic fibromyxoma in a red tail boa (Boa constrictor constrictor) with inclusion body disease

A captive bred red tail boa (Boa constrictor constrictor) was presented with a large intraoral mass originating from the buccal gingiva, attached to the right dentary teeth row. Based on the clinical features and histological examination, the diagnosis of a peripheral odontogenic fibromyxoma was made. Sections of liver biopsies and circulating lymphocytes contained relatively few eosinophilic intracytoplasmic inclusion bodies, indistinguishable from those observed in inclusion body disease-affected snakes. Inclusion bodies were not observed in cells comprising the neoplastic mass. Using reverse transcription polymerase chain reaction (RT-PCR), arenavirus was detected in the neoplastic tissue. Two years after surgical removal of the mass, recurrence of the neoplastic lesion was observed. Numerous large inclusion body disease inclusions were abundantly present in the neoplastic cells of the recurrent fibromyxoma. Sections of liver biopsies and circulating lymphocytes contained relatively few intracytoplasmic inclusions. The RT-PCR revealed the presence of arenavirus in blood, a liver biopsy, and neoplastic tissue. The present case describes the co-occurrence of an arenavirus infection and an odontogenic fibromyxoma in a red tail boa

Stress in wild and captive snakes : quantification, effects and the importance of management

As in other animals, distress and impaired welfare have a deleterious effect on the mental, physical and behavioral health of snakes in the wild and in captivity. Besides anthropogenic disturbance, the availability of food and shelter, the presence of predators, and environmental factors, such as seasonality and climatological changes, are important factors that affect the stress level and subsequent welfare in wild snake populations. In captive snakes, inappropriate management is the most prominent cause of chronic stress and impaired welfare. Chronic stress can be assumed by looking at the snake's behavior, but there is need for a standardized quantification method to pin-point more accurately (chronic) stress levels. The biomarker suitable in this framework is the level of corticosterone in plasma, feces and shed skin