Increasing incidence of Geomyces destructans fungus in bats from the Czech Republic and Slovakia

Abstract

Background: White-nose syndrome is a disease of hibernating insectivorous bats associated with the fungus Geomyces destructans. It first appeared in North America in 2006, where over a million bats died since then. In Europe, G. destructans was first identified in France in 2009. Its distribution, infection dynamics, and effects on hibernating bats in Europe are largely unknown.

Methodology/principal findings: We screened hibernacula in the Czech Republic and Slovakia for the presence of the fungus during the winter seasons of 2008/2009 and 2009/2010. In winter 2009/2010, we found infected bats in 76 out of 98 surveyed sites, in which the majority had been previously negative. A photographic record of over 6000 hibernating bats, taken since 1994, revealed bats with fungal growths since 1995; however, the incidence of such bats increased in Myotis myotis from 2% in 2007 to 14% by 2010. Microscopic, cultivation and molecular genetic evaluations confirmed the identity of the recently sampled fungus as G. destructans, and demonstrated its continuous distribution in the studied area. At the end of the hibernation season we recorded pathologic changes in the skin of the affected bats, from which the fungus was isolated. We registered no mass mortality caused by the fungus, and the recorded population decline in the last two years of the most affected species, M. myotis, is within the population trend prediction interval.

Conclusions/significance: G. destructans was found to be widespread in the Czech Republic and Slovakia, with an epizootic incidence in bats during the most recent years. Further development of the situation urgently requires a detailed pan-European monitoring scheme.

Figure 1. White-nose syndrome symptoms in the Czech Republic and Slovakia.

(A) Hibernating M. myotis in the Javoříčské Caves, Czech Republic, photographed on 25 January 1997. Fungal growth was not identified. (Photo by Jiří Šafář) (B) Skin lesions on M. myotis from the Malá Amerika Mines, Karlštejn, Czech Republic, photographed on 16 March 2010. G. destructans, isolate number CCF3942, was isolated from the sample taken from the lesion. (Photo by Ivan Horáček).

Figure 2. Occurrence of Geomyces destructans in the Czech Republic and Slovakia.

(A) Distribution of WNS on the background of localities targeted for WNS screening. Some circles represent more than one hibernaculum. White circles -localities censused in 2009 and 2010; black circles - localities with WNS-suspect bats; stars - localities with photographic evidence of WNS in 2007 and 2008. (B) Prevalence of WNS-suspect individuals from Myotis myotis populations. Data pooled according to region; circle size is proportional to the population size.

Figure 3. Spores and colonies of G. destructans.

(A) Adhesive tape sample from the lesion of M. myotis photographed in Figure 1B, locality Malá Amerika Mines, Karlštejn, Czech Republic (Phase contrast). (B) G. destructans CCF3937. Conidiophores and arthroconidia (SDA, 14 days, 15°C, phase contrast). (C) Primary isolation of G. destructans CCF3942 (SDA, 1 month, 15°C). (D) Growth characteristics of G. destructans on four agar media at c. 15°C.

Figure 4. Upward population trends of hibernating M. myotis.

In the Czech (A) and Slovak Republic (B) the trends were modelled over the period 1995–2010 by fitting Poisson regression allowing for over-dispersion in the data. The point prediction (solid line) and 95% prediction intervals (shaded area) are based on observations up to 2008 (solid symbols) and then extrapolated to 2009 and 2010. The open symbols represent observed data for 2009 and 2010.