Chytridiomycosis: An Emerging Infectious Disease of Amphibians Road map • What is Chytridiomycosis • Signs of disease • Origins of pathogen • Case study “El Cope panama” • Current efforts • Future efforts The problem • Amphibian population declines • Many proposed causes of amphibian declines • Most noticeable 1980s-present • Greatest concern = “enigmatic” or mysterious declines – Remote, protected areas – No obvious causes – Sudden massive die-offs, lack of recovery • Many enigmatic declines attributed to Chytrid fungus (Bd) – most tropical, montane, riparian The pathogen • Batrachochytrium dendrobatidis (Bd): – Emerging infectious disease of amphibians – First chytrid fungus pathogenic to vertebrates • Infect keratinized tissue – Mouthparts in larvae – Adult skin • 3 life stages – Zoospore – aquatic, flagellated (3-5μm) – Thallus – in epidermis – Zoosporangium – zoospores discharged Histological Signs Epidermis Discharge Tube D. Miller Zoosporangia Proliferation of Epidermal Cells Stratum Corneum Epidermal Hyperplasia Normal Thickness: 2 – 5 m Sloughing Infected: 60 m Clinical signs: in field • Infected individuals appear healthy • Lethargic • Sloughing skin • Loss & depigmentation in mouthparts of larvae Erythema oPfe lteegcsh aiantdio vne ntrum Cutaneous erosions and ulcerations Loss of muscle control Death Bd Ecology • Environmentally sensitive – Cool temperatures: 17-24˚C (killed if >30˚C) – Moist environments (killed by desiccation) – No resting stage • Environmental persistence – Up to 7 weeks in pond water (Johnson and Speare 2003) – Up to 6 weeks in mesocosm – At least 3 days in the environment