Batrachochytrium salamandrivorans (Bsal) is an invasive fungal pathogen that is emerging in Europe and appears to be highly pathogenic to many salamander species, particularly those in the family Salamandridae. The Eastern Newt (Notophthalmus viridescens) is a member of Salamandridae and known to be susceptible to Bsal. This species is one of the most widely distributed salamanders in North America. Given their widespread distribution and high abundance, this species has the potential to significantly influence Bsal epidemiology if the pathogen emerges in the United States. We designed two studies to estimate contact rates given different host densities and habitat structure, and the probability of transmission from infected to susceptible individuals via direct contact. Using parameter estimates from these controlled experiments, we modeled infection and disease outcomes for a population of eastern newts using a system of ordinary differential equations.
Results/Conclusions
We found that Bsal transmission due to contact was very efficient between infected and susceptible newts even at early stages of infection when pathogen loads were low. We also found that contact rates were density dependent, and that adding habitat structure (i.e., aquatic plants) reduced host contacts at higher newt densities. Our simulations show rapid transmission of Bsal among individuals, such that an entire population can become infected in less than one month, and mortality can exceed 90% in three months. These results demonstrate that Bsal can have severe population impacts on eastern newts. Moreover, this abundant amphibian species could play a major role in Bsal emergence if the pathogen is introduced in the USA. Reducing newt density or increasing habitat structure at Bsal positive sites might be a reasonable disease mitigation strategy to reduce Bsal transmission and outbreak size.