Data from: Elevated salinity blocks pathogen transmission and improves host survival for a globally pandemic disease: implications for amphibian translocations

1. Emerging infectious diseases are one of the greatest threats to global
biodiversity. Chytridiomycosis in amphibians is perhaps the most extreme
example of this phenomenon known to science. Translocations are
increasingly used to fight disease-induced extinctions. However, many
programs fail because disease is still present or subsequently establishes
in the translocation environment. There is a need for studies in
real-world scenarios to test whether environmental manipulation could
improve survival in populations by generating unfavourable environmental
conditions for pathogens. Reintroductions of amphibians impacted by
chytridiomycosis into environments where the disease persists provide a
scenario where this paradigm can be tested. 2. We tested the hypothesis
that manipulating environmental salinity in outdoor mesocosms under near
identical environmental conditions applying in a nearby translocation
program for an endangered amphibian, would improve survival and determine
the mechanisms involved. 160 infected and 288 uninfected, captive-bred,
juvenile frogs were released into 16 outdoor mesocosms in which salinity
was controlled (high or low salinity treatment). The experiment was run
for 25 weeks from the mid-austral winter to the mid-austral summer of 2013
in a temperate coastal environment, Australia. 3. Increasing salinity from
ca. 0.5 ppt to 3.5 - 4.5 ppt reduced pathogen transmission between
infected and uninfected animals, resulting in significantly reduced
mortality in elevated salt mesocosms (0.13, high salt versus 0.23, low
salt survival at 23 weeks). Increasing water temperature associated with
season (from mean 13oC to 25oC) eventually cleared all surviving animals
of the pathogen. 4. Synthesis and applications. We identified a mechanism
by which environmental salinity can protect amphibian hosts from
chytridomycosis by reducing disease transmission rates and conclude that
manipulating environmental salinity in landscapes where chytrid-affected
amphibians are currently translocated could improve the probability of
population persistence for hundreds of species. More broadly, we provide
support for the paradigm that environmental manipulation can be used to
mitigate the impact of emerging infectious diseases.18-Sep-2017