Amphibian Fungal Disease Dynamics

Chytridiomycosis fungus dynamics in wildlife

Gabriela Rios-SoteloVance Vredenburg LabSan Francisco State University

Amphibian diversity

Emerging disease

• Number 1 most threatened vertebrate

• 1/3 (32%) of amphibians are threatened species

• May be on the brink of a sixth mass extinction

• Many reasons for declines

• Recently…

INFECTIOUS DISEASE

Global amphibian declines

Emerging disease

Chytridiomycosis (chytrid) Largest disease-caused loss of species in

history 200 species already driven to extinction Fungal pathogen specific to amphibians Transmitted by aquatic zoospores Infects keratin layers of amphibian skin Thickened skin leading to blocked osmotic

regulation and electrolyte transport

Skerratt et al 2007; Voyles et al 2009

Batrachocytrium dendrobatidis(Bd) lifecycle

Many questions… Where did this disease originate? How did amphibians in

this area come to live robustly with this fungus? Can we use this knowledge to efficiently protect other species worldwide?

How can we control further disease spread? How do some species survive with infection while others do

not? How does this particular microbe interact as a skin disease?

Does it compete for food and space with other skin microbes? Does this have to do with why some species are more susceptible than others?

How does Bd’s assn. with it’s abiotic environment influence it’s dispersal, susceptibilty and other factors?

Chytrid Dynamics

Worldwide distribution

Fisher et al 2009

?

Bd has been well documented all over the world except Asia

Emerging disease in Asia

Bd in Asia Most unique and diverse areas in the

world for amphibian fauna Recent papers in China, Japan and South

Korea show low infection rates and no signs of mass amphibian declines

Emerging disease in Asia

Disease Dymanics Two hypothesis for Bd emergence

Novel pathogen hypothesis (NPH) Emerging endemic hypothesis (EEH)

EEH pattern would show constant infection prevalence levels demonstrating coevolution in area of origin

Berger et al 1998; Rashowicz et al 2005; Pounds et al 2006

Emerging disease in Asia

K Upton

Bd in Japan

1st distribution of Bd in Japan Low infection rates Many haplotypes Vector mediated spread

Emerging disease in Asia

AS well as the oldest museum specimen record documented with Bd

1902 Andrias japonicus

K Sweet 2008

Emerging disease in Asia

Using museum specimens and PCR to test for Bd New method developed From Dr. Alex Hyatt’s PCR detection method adapted by Tina Cheng allows Bd detection in preserved museum specimens

Emerging disease in Asia

Bd disease Map of Japan

Emerging disease in Asia