Jul 24 2019
According to new research reported in mBio—an open-access journal of the American Society for Microbiology—global warming may have had a key role in the rise of Candida auris.
A serious public health threat and often multi-drug resistant fungi, C. auris may be the first example of a new fungal disease caused as a result of climate change.
The argument that we are making based on comparison to other close relative fungi is that as the climate has gotten warmer, some of these organisms, including Candida auris, have adapted to the higher temperature, and as they adapt, they break through human’s protective temperatures. Global warming may lead to new fungal diseases that we don’t even know about right now.
Arturo Casadevall, MD, PhD, Chair, Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health
C. auris broke out independently on three continents at the same time, with each clade being genetically unique.
“What is unusual about Candida auris is that it appeared in three different continents at the same time, and the isolates from India, South Africa, and South America are not related. Something happened to allow this organism to bubble up and cause disease,” stated Dr Casadevall.
He continued, “We began to look into the possibility that it could be climate change. The reasons that fungal infections are so rare in humans are that most of the fungi in the environment cannot grow at the temperatures or our body.”
The resistance of mammals to invasive fungal diseases is due to a combination of high basal temperatures that develop a thermal restriction zone and complex host defense mechanisms in the form of innate and adaptive immunity.
In the new research, the scientists related the thermal susceptibility of C. auris to some of its close phylogenetic relatives. The scientists found that C. auris can breed at higher temperatures when compared to a majority of its closely linked species, which were intolerant to mammalian temperatures. According to the scientists, adaption to higher temperatures is one contributing reason for the occurrence of C. auris.
“What this study suggests is this is the beginning of fungi adapting to higher temperatures, and we are going to have more and more problems as the century goes on,” stated Dr Casadevall. “Global warming will lead to selection of fungal lineages that are more thermally tolerant, such that they can breach the mammalian thermal restriction zone.”
Dr. Casadevall noted that if better surveillance systems were available, the emergence of C. auris would have been identified earlier.
We need to make investments in better surveillance of fungal diseases. We are pretty good at surveilling influenza and diseases that cause diarrhea or are contagious, but fungal diseases are not usually contagious and therefore nobody has really bothered to document them well. If more fungi were to cross over, you really wouldn’t know until somebody started reporting them in the literature.
Arturo Casadevall, MD, PhD, Chair, Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health
Source: https://www.asm.org/