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Atherton, Australia

Skerratt L.F.,James Cook University | Mendez D.,James Cook University | McDonald K.R.,Amphibian Disease Ecology Group | Garland S.,James Cook University | And 3 more authors.
Journal of Herpetology

We validated the diagnostic tests for the high-profile disease, chytridiomycosis, in wild amphibian populations. We compared histological samples with a Taqman real time quantitative PCR (qPCR) test in five species of frogs at different times of the year at six locations in the wet tropics of northern Queensland. The sensitivity and specificity of each test were estimated using prior estimates from previous laboratory studies and Bayesian methods. The qPCR test was almost three times as sensitive 72.9% (62.782.2%) than histology 26.5% (19.933.9%) but was less specific 94.2% (89.398.6%) than histology 99.5% (98.4100%), which was likely caused by contamination. Monitoring of the negative control success rate of the qPCR test is potentially a good indicator of specificity. It is likely that using individual gloves for handling amphibians reduces cross-contamination and, therefore, improves specificity rather than cause inhibition of the qPCR. Classifying indeterminate results as positive will increase the qPCR test sensitivity but will lower specificity to a lesser degree depending on the likelihood of contamination. Although PCR is the preferred test for amphibian populations, histology is useful when wishing to confirm a diagnosis of infection and in situations where observing the severity of infection and pathology in skin is desired. In this study, we show that diagnostic test validation in wild animals is now relatively straight forward using modern computing power and can incorporate prior knowledge generated from laboratory studies using Bayesian approaches. Copyright 2011 Society for the Study of Amphibians and Reptiles. Source

Skerratt L.F.,James Cook University | McDonald K.R.,Amphibian Disease Ecology Group | Hines H.B.,Queensland Parks and Wildlife Service | Berger L.,James Cook University | And 5 more authors.
Diseases of Aquatic Organisms

Spread of the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis, has resulted in the extinction of frogs, but the distribution of Bd is incompletely known. We trialled the survey protocol for Bd by attempting to systematically map its distribution in Queensland, Australia. Bd was easily detected in known infected areas, such as the Wet Tropics and South East Queensland. It was not detected in bioregions adjacent to, but inland from or to the north of, infected regions: Einasleigh Uplands and Cape York adjacent to the infected Wet Tropics; and Brigalow Belt South adjacent to the infected South East Queensland bioregion. These regions where Bd was not detected have bordered infected regions for between 15 yr (in northern Queensland) and 30 yr (in southern Queensland), and so they define the geographical limits of Bd with regard to the long-term environmental conditions in Queensland. The Gulf Plains, a bioregion distant from infected bioregions, was also negative. Bd was confined to rainforest and bordering habitats, such as wet eucalypt forests. Infections were largely confined to permanent water-associated species, consistent with this being an important cause of this group having the greatest declines. Our data supports biogeographic climatic models that show much of inland and northern Australia to be too hot and dry to support Bd. As there is limited opportunity for Bd to spread further in Queensland, the priority for management is reducing the impact of Bd in affected populations and assisting frogs to disperse into their former distributions. Given that the survey protocol has been applied successfully in Australia it may be useful for mapping the distribution of Bd in other parts of the world. © Inter-Research 2010. Source

Young S.,Amphibian Disease Ecology Group | Warner J.,James Cook University | Speare R.,Amphibian Disease Ecology Group | Berger L.,Amphibian Disease Ecology Group | And 2 more authors.
Veterinary Clinical Pathology

Background: Few hematologic and biochemical reference intervals for wild amphibians have been established. Reference values would aid in early detection of emerging infectious diseases, which are a significant problem for amphibian conservation efforts. Objective: We aimed to establish reference intervals for a wide range of hematologic and plasma biochemistry variables for 2 species of Australian tree frogs, describe morphologic features of leukocytes, and analyze the effects of season, year, and parasite status on blood values. Methods: Blood specimens were collected from reference populations of wild adult Australian tree frogs, Litoria caerulea and L infrafrenata, for analysis of hematologic (manual) variables, plasma biochemical (automated) analytes, and plasma and serum proteins using automated methods, refractometry, and electrophoresis. Results: Inter- and intraspecies differences were found in L caerulea (n = 80) and L infrafrenata (n = 66) frogs for hematologic and biochemical variables. Intraspecies differences were largely associated with seasonal variations. In the dry season, both species had higher WBC counts, with higher lymphocyte counts in L caerulea and higher neutrophil counts in L infrafrenata, and uric acid concentrations. In the wet season, both species had higher glucose and potassium concentrations, L caerulea frogs had higher neutrophil counts, and L infrafrenata frogs had higher total protein, phosphorus, and sodium concentrations, AST activity, PCV, hemoglobin concentration, and RBC, thrombocyte, and basophil counts. Hemogregarines were identified in 19% of blood samples from L infrafrenata frogs; multiple hematologic and biochemical variables were altered in infected frogs. Conclusions: Wide interspecies and seasonal variations highlight the need to establish species- and season-specific reference intervals for amphibians. Hematologic and plasma biochemical reference values should be useful in assessing the health status and in detecting emerging diseases in wild amphibians. © 2012 American Society for Veterinary Clinical Pathology. Source

Young S.,Amphibian Disease Ecology Group | Skerratt L.F.,Amphibian Disease Ecology Group | Mendez D.,Amphibian Disease Ecology Group | Speare R.,Amphibian Disease Ecology Group | And 2 more authors.
Diseases of Aquatic Organisms

We analyzed submission data from a wildlife care group during amphibian disease surveillance in Queensland, Australia. Between January 1999 and December 2004, 877 whitelipped tree frogs Litoria infrafrenata were classified according to origin, season and presenting category. At least 69% originated from urban Cairns, significantly more than from rural and remote areas. Total submissions increased during the early and late dry seasons compared with the early wet season. Frogs most commonly presented each year with injury, followed by 'other', sparganosis and irreversible emaciation of unknown aetiology. This is the first report of Spirometra erinacei in - fection in this species. A high prevalence (28%) of visible S. erinacei infection was found in emaciated frogs, but this was not statistically different from that in non-emaciated diseased frogs (25%). However, 14 emaciated specimens that were necropsied all had heavy S. erinacei infections, and the odds of visible sparganosis were statistically greater in emaciated frogs compared with injured, non-diseased frogs. We provide a detailed case definition for a new en demic disease manifesting as irreversible emaciation, for which S. erinacei may be the primary aetiological agent. The lack of significant spatial or temporal patterns in case presentation suggests that this is not a currently emerging disease. We show that community wildlife groups can play a valuable role in monitoring disease trends, particularly in urban areas, but identify a number of limitations associated with passive syndromic surveillance. We conclude that it is critical that professionals be involved in establishing syndromic case definitions, diagnostic pathology, complementary active disease surveillance, and data analysis and interpretation in all wildlife disease investigations. © Inter-Research 2012. Source

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