Emerging infectious diseases (EIDs) of free-living wild animals can be classified into three major groups on the basis of key epizootiological criteria: (i) EIDs associated with "spill-over" from domestic animals to wildlife populations living in proximity; (ii) EIDs related directly to human intervention, via host or parasite translocations; and (iii) EIDs with no overt human or domestic animal involvement. These phenomena have two major biological implications: first, many wildlife species are reservoirs of pathogens that threaten domestic animal and human health; second, wildlife EIDs pose a substantial threat to the conservation of global biodiversity.

Batrachochytrium dendrobatidis is a major pathogen of frogs worldwide, associated with declines in amphibian populations. Diagnosis of chytridiomycosis to date has largely relied upon histological and immunohistochemical examination of toe clips. This technique is invasive and insensitive particularly at early stages of infection when treatment may be possible. We have developed a real-time PCR Taqman assay that can accurately detect and quantify one zoospore in a diagnostic sample. This assay will assist the early detection of B. dendrobatidis in both captive and wild populations, with a high degree of sensitivity and specificity, thus facilitating treatment and protection of endangered populations, monitoring of pristine environments and preventing further global spread via amphibian trade. KEY WORDS: Chytrids · Batrachochytrium dendrobatidis · Amphibian declines · Real-time PCR Taqman assay · Chytridiomycosis Resale or republication not permitted without written consent of the publisherDis Aquat Org 60: [141][142][143][144][145][146][147][148] 2004 examination via haematoxylin and eosin staining of toe clips or skin scrapings (Daszak et al. 1999, see also www.jcu.edu.au/school/phtm/phtm/frogs/histo/ chhisto.htm). Immunoperoxidase staining with polyclonal antibodies to B. dendrobatidis increases the specificity and sensitivity of detection (Berger et al. 2002). More recently, a staining protocol has been described which enhances diagnosis by the colocalisation of B. dendrobatidis and keratin in the skin of amphibians (V. Olsen, D. Boyle, D. Mendez, A. D. Hyatt unpubl.). However, the drawbacks of histological testing include the degree of expertise needed for identification, the invasiveness of sampling technique -typically performed by toe-clipping of live animals -the length of time required, the low sensitivity of the test, and the variability of infection levels amongst toes. In the field, examination of oral disc abnormalities in tadpoles with a 10 × hand lens has been recommended as a preliminary indication of chytridiomycosis (Fellers et al. 2001), although these abnormalities can also be caused by DDT intoxication. The fungus can be identified by isolation and culture , but this requires a high degree of expertise and time.Early detection of Batrachochytrium dendrobatidis is vital to the control of spread of the disease via global amphibian trade. B. dendrobatidis has been identified in animals imported for zoo collections , in international pet trade (Mutschmann et al. 2000), in the food trade (Mazzoni et al. 2003) and in laboratory animal trade (Parker et al. 2002). Early detection of infection would allow possible curative treatment to be undertaken, at least in captive populations where formalin/malachite green solution has been shown to be effective on adult Xenopus tropicalis (Parker et al. 2002). Itraconazole baths (0.01%) were found to be effective in treating the terrestrial species Dendrobates tinctorius (Nichols et al. 2001), although whether this treatment is effective and safe...

Batrachochytrium dendrobatidis is a fungus belonging to the Phylum Chytridiomycota, Class Chytridiomycetes, Order Chytridiales, and is the highly infectious aetiological agent responsible for a potentially fatal disease, chytridiomycosis, which is currently decimating many of the world's amphibian populations. The fungus infects 2 amphibian orders (Anura and Caudata), 14 families and at least 200 species and is responsible for at least 1 species extinction. Whilst the origin of the agent and routes of transmission are being debated, it has been recognised that successful management of the disease will require effective sampling regimes and detection assays. We have developed a range of unique sampling protocols together with diagnostic assays for the detection of B. dendrobatidis in both living and deceased tadpoles and adults. Here, we formally present our data and discuss them in respect to assay sensitivity, specificity, repeatability and reproducibility. We suggest that compliance with the recommended protocols will avoid the generation of spurious results, thereby providing the international scientific and regulatory community with a set of validated procedures which will assist in the successful management of chytridiomycosis in the future.

We review recent research on the pathology, ecology, and biogeography of two emerging infectious wildlife diseases, chytridiomycosis and ranaviral disease, in the context of host-parasite population biology. We examine the role of these diseases in the global decline of amphibian populations and propose hypotheses for the origins and impact of these panzootics. Finally, we discuss emerging infectious diseases as a global threat to wildlife populations.

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Abstract. A series of recent papers have implicated pathogens and parasites in amphibian population declines. Here, we review evidence on the link between infectious disease and amphibian population declines. We conclude that available data provide the clearest link for the fungal disease amphibian chytridiomycosis, although other pathogens are also implicated. We suggest additional experimental and observational data that need to be collected to provide further support that these other pathogens are associated with declines. We suggest that, in common with many emerging infectious diseases (EIDs) of humans, domestic animals and other wildlife species, emergence of chytridiomycosis may be driven by anthropogenic introduction (pathogen pollution). Finally, we review a number of recent advances in the host–parasite ecology of chytridiomycosis that help explain its emergence and impact.

A morbillivirus has been isolated and added to an increasing list of emerging viral diseases. This virus caused an outbreak of fatal respiratory disease in horses and humans. Genetic analyses show it to be only distantly related to the classic morbilliviruses rinderpest, measles, and canine distemper. When seen by electron microscopy, viruses had 10- and 18-nanometer surface projections that gave them a "double-fringed" appearance. The virus induced syncytia that developed in the endothelium of blood vessels, particularly the lungs.

Histologic evidence indicates southern Africa as the origin of the amphibian chytrid fungus.