Batrachochytrium salamandrivorans is the predominant chytrid fungus in Vietnamese salamanders

Abstract

The amphibian chytrid fungi, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), pose a major threat to amphibian biodiversity. Recent evidence suggests Southeast Asia as a potential cradle for both fungi, which likely resulted in widespread host-pathogen co-existence. We sampled 583 salamanders from 8 species across Vietnam in 55 locations for Bsal and Bd, determined scaled mass index as a proxy for fitness and collected environmental data. Bsal was found within 14 of the 55 habitats (2 of which it was detected in 2013), in 5 salamandrid species, with a prevalence of 2.92%. The globalized pandemic lineage of Bd was found within one pond on one species with a prevalence of 0.69%. Combined with a complete lack of correlation between infection and individual body condition and absence of indication of associated disease, this suggests low level pathogen endemism and Bsal and Bd co-existence with Vietnamese salamandrid populations. Bsal was more widespread than Bd, and occurs at temperatures higher than tolerated by the type strain, suggesting a wider thermal niche than currently known. Therefore, this study provides support for the hypothesis that these chytrid fungi may be endemic to Asia and that species within this region may act as a disease reservoir.

Figure 1. Map of sampling locations within Northern Vietnam.

The size of the pie charts corresponds to the sample size ranging from 1 to 44 individuals. The pie chart indicates the prevalence of Bsal (Red) or Bd (Blue) within that population. This map was generated in ArcMap 10.1 (http://www.esri.com/software/arcgis/arcgis-for-desktop).

Figure 2. Prevalence of Bd and Bsal positive salamanders at each positive location (pond or stream), and its corresponding water temperature.

*Only one individual was sampled at this location.