Data from: Initiation of Batrachochytrium dendrobatidis infection in the absence of physical contact with infected hosts – a field study in a high altitude lake

Understanding transmission is a critical prerequisite for predicting
disease dynamics and impacts on host populations. It is well established
that Batrachochytrium dendrobatidis (Bd), the amphibian fungal pathogen
responsible for chytridiomycosis, can be transmitted directly, through
physical contact with an infected host. However, indirect pathways of
transmission remain poorly investigated. We conducted a five-week long
field infection experiment at a high altitude mountain lake in the French
Pyrenees to investigate Bd transmission pathways in larval midwife toads
Alytes obstetricans. Uninfected naïve tadpoles were co-housed either with
infected tadpoles (direct and indirect transmission) or with uninfected
ones (indirect transmission only). We found that physical contact with an
infected host is not necessary for initial infection with Bd and that all
tadpoles became infected after only four weeks. However, physical contact
with infected tadpoles led to a faster spread within a tadpole group and
resulted in higher Bd loads and subsequently higher mortality. Our
findings clearly demonstrate that in A. obstetricans, Bd can quickly
spread in a population even without physical contact. Our experiment
therefore stresses the importance of indirect transmission of Bd zoospores
in infected lakes for disease dynamics, especially when a reservoir
species such as A. obstetricans is present.