A Brevia piece in Science today describes efforts to describe the causal agent in white-nose syndrome (WNS) in bats which appears to be contributing to bat decline. According to the authors, previous work had described an uncharacterized fungus associated with bats that showed signs of being sick with WNS. This is an emerging pathogen as the samples described in this paper were from Spring 2008. Phylogenetic analysis of the rDNA (and presumably ITS) sequence of fungal isolates from diseased bats placed it as a Geomyces spp, in the Helotiales order (in the Leotiomycetes if you are wondering what are the closest sequenced fungal genomes for this species). Other Geomyces spp are also psychrophiles and found colonizing the skin of animals in cold climates (it must be hard to make a living). The authors suggest the finding of this fungal species on bats is consistent with its involvement in disease. The authors also make the parallel to chytridiomycosis, an emerging pathogen of amphibians that is contributing to the worldwide amphibian decline.
This is just the first of hopefully several publications studying this phenomenon as this brief piece sets the stage for additional questions. It is not yet been shown that this fungus is actually causing the disease, i.e. satisfying Koch’s postulates, and isn’t just a canary in the coal mine. So-called opportunistic fungi like Aspergillus fumigatus, Cryptococcus neoformans, and Candida albicans cause infections that emerge after the patient’s immune system has been compromised by something else such as HIV or immunosuppressant drugs as part of an organ transplant regime. It is possible that the white-nose syndrome (ie white conidia from Geomyces sp is just a manifestation of an infection of a commensal organism like thrush or yeast infections of Candida albicans that only emerge when something else has knocked down the host’s immune system. I don’t know if this same Geomyces sp can be cultured from healthy bats from so-far uninfected colonies which would suggest the fungus is present all the time.
As we track and learn more about natural die-offs and disease in animals from infectious diseases there are series of recent fungal-associated disease of animal populations including honeybees perhaps from a virus and a microsporidium, frogs and amphibians via Batrachochytrium dendrobatidis, and white-nose syndrome. Diseases like Cryptococcus gattii are also examples of pathogens that may be able to infect healthy animals and humans. It seems quite important to know more important to track and study how these outbreaks spread and the evolutionary and ecological basis for the sudden rise in infection and mortality in animal populations to understand diseases of human relevance as well.
- Bats beware of white-nose
- Some links (where we mention another Psychrophilic fungus
- Nature blogs story
D. S. Blehert, A. C. Hicks, M. Behr, C. U. Meteyer, B. M. Berlowski-Zier, E. L. Buckles, J. T. H. Coleman, S. R. Darling, A. Gargas, R. Niver, J. C. Okoniewski, R. J. Rudd, W. B. Stone (2008). Bat White-Nose Syndrome: An Emerging Fungal Pathogen? Science DOI: 10.1126/science.1163874