Short report: Batrachochytrium dendrobatidis in amphibians in the Netherlands and Flanders (Belgium)

Goal Determine presence of the zoosporic fungus Batrachochytrium dendrobatidis, the causative agent of the amphibian skin disease chytridiomycosis, in free ranging amphibians in the Netherlands and Flanders (Belgium) Methods Volunteers and professionals collected data from free ranging amphibians by stroking 3 – 5 times with a sterile cotton-tipped dryswab over the underside of the legs, feet and drink patch. All amphibians were individually sampled. Hygienic measurements were taken to prevent cross-infection. Quantitative real-time TaqMan PCR assays were performed for the determination of Bd infections. A total of 2,771 swabs were collected between August – October 2008 (American bullfrogs in Flanders) and between March – September 2009 (all species in the Netherlands and in Flanders). Samples were collected in all provinces and all species apart from the marsh frog were sampled. Results Bd infected amphibians have been found all over the Netherlands, in all provinces apart from Groningen, Zuid-Holland and Zeeland. A total of 4% of all amphibians in the Netherlands (3.7%) and Belgium (5.4%) are infected with Bd. Critically endangered, endangered and vulnerable amphibian species are infected Bd was found in all native species apart from the common spadefoot (low sample size) and the mars frog (no data collected). The smooth newt was the most sampled species of all amphibians. None of the infected individuals showed any visible symptoms. We carefully suggest that Bd can be found in all amphibians over the whole of the Netherlands. Discussion & recommendations No data on prevalence can be calculated due to ad hoc sampling and the impact of Bd infections on native species is yet unknown. Phylogenetic analyses of Bd haplotypes will give insight in the virulence of the strains and the process of invasion into the Netherlands and Flanders. Studying the relationship between aquatic stress and the virulence of Bd will help in the determination of the true risk for the survival of amphibian populations as well as the study of the ecology of Bd in the European temperate climate zone. Simultaneously, vulnerable populations like the midwife toad should be monitored intensively to prevent catastrophic declines that cannot be reversed. We face the enormous challenge to define the true impact of Bd infection on native amphibians and at the same time, find means of prevention and cure to sustain amphibian populations.

Jaar van publicatie:2010