Widespread occurrence of an emerging fungal pathogen in heavily traded Chinese urodelan species

Zhiyong Yuan,Stefano Canessa,An Martel,Frank Pasmans,Jun Wu,Sarah Van Praet

doi:10.1111/conl.12436

Abstract

AbstractUnderstanding introduction routes for wildlife pathogens is vital for the development of threat abatement plans. The chytrid fungus Batrachochytrium salamandrivorans (Bsal) has recently emerged in Europe, where it is considered to be a serious threat for urodelan conservation. If the highly diverse Chinese urodelans were to constitute a Bsal reservoir, then the significant international trade in these species may vector Bsal into naïve urodelan communities. Here, we analyzed a total of 1,143 samples, representing 36 Chinese salamander species from 51 localities across southern China for the presence of Bsal. We found Bsal was present across a wide taxonomic, geographical, and environmental range. In particular, Bsal DNA was detected in 33 samples from the genera Cynops, Pachytriton, Paramesotriton, Tylototriton, and Andrias, including the heavily traded species Paramesotriton hongkongensis and Cynops orientalis. The true Bsal prevalence across our data set was estimated between 2% and 4%, with a maximum of 50% in a population of P. hongkongensis. Even at this overall relatively low Bsal prevalence, the exportation of millions of animals renders Bsal introduction in naïve, importing countries a near certainty, which calls for the urgent implementation of proper biosecurity in the international wildlife trade.

Highlights

2 MATERIALS AND METHODSEmerging fungal diseases are major drivers of global amphibian diversity loss (Fisher et al, 2012)
Quantifying the prior belief about the probability of presence and prevalence of the pathogen is key to devising effective biosecurity control and surveillance monitoring (Runge et al, 2017). We present this evidence, obtained from a large-scale field sampling for Batrachochytrium salamandrivorans (Bsal) in Chinese urodelans, including the most widely traded salamandrid genera, which demonstrates presence of Bsal in several trade species, and remarkably high prevalence in some of them
The mean true prevalences at the level of individual species, genera, or provinces always fell within the range 0.01-0.06, with the exception of Guangdong Provence where high prevalence was largely determined by the above mentioned P. hongkongensis population (Figure 2)

Summary

MATERIALS AND METHODS

Emerging fungal diseases are major drivers of global amphibian diversity loss (Fisher et al, 2012). Quantifying the prior belief about the probability of presence and prevalence of the pathogen is key to devising effective biosecurity control and surveillance monitoring (Runge et al, 2017) We present this evidence, obtained from a large-scale field sampling for Bsal in Chinese urodelans, including the most widely traded salamandrid genera, which demonstrates presence of Bsal in several trade species, and remarkably high prevalence in some of them. We assumed the number n of infected individuals out of a sample of size N to be a binomially distributed random variable n∼Bin (p, N), where p is the true prevalence of infection in the sampled population This estimate provides a more realistic representation of our current knowledge of Bsal prevalence, and can, for example, be used as a prior belief for the design of surveillance monitoring and biosecurity controls. We used logistic regression to model p across the entire data set as a linear

RESULTS

Findings

DISCUSSION