Affiliation:
1. Department of Infectious Disease Epidemiology, Imperial CollegeSt Mary's Campus, Norfolk Place, London W2 1PG, UK
2. The Institute of Zoology, Zoological Society of LondonRegent's Park, London NW1 4RY, UK
Abstract
Pathogens do not normally drive their hosts to extinction; however,
Batrachochytrium dendrobatidis
, which causes amphibian chytridiomycosis, has been able to do so. Theory predicts that extinction can be caused by long-lived or saprobic free-living stages. The hypothesis that such a stage occurs in
B. dendrobatidis
is supported by the recent discovery of an apparently encysted form of the pathogen. To investigate the effect of a free-living stage of
B. dendrobatidis
on host population dynamics, a mathematical model was developed to describe the introduction of chytridiomycosis into a breeding population of
Bufo bufo
, parametrized from laboratory infection and transmission experiments. The model predicted that the longer that
B. dendrobatidis
was able to persist in water, either due to an increased zoospore lifespan or saprobic reproduction, the more likely it was that it could cause local
B. bufo
extinction (defined as decrease below a threshold level). Establishment of endemic
B. dendrobatidis
infection in
B. bufo
, with severe host population depression, was also possible, in agreement with field observations. Although this model is able to predict clear trends, more precise predictions will only be possible when the life history of
B. dendrobatidis,
including free-living stages of the life cycle, is better understood.
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
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