New Species of Fungus Can be Deadly for Cats and Humans

A tumor-like fungal growth that can cause life-threatening infections in humans and cats has been identified as a new species of fungus.

Vanessa Barrs, a researcher at the University of Sydney's school of veterinary science, first noticed the fungal infection present in three cats she treated in 2006.

"These cats presented with a tumor-like growth in one of their eye sockets, that had spread there from the nasal cavity," Barrs said in a news release. "The fungal spores are inhaled and in susceptible cats they establish a life-threatening infection that is very difficult to treat."

She spent the following six years investigating the mysterious fungus with some of the world's leading fungal experts.

"Finally I was able to confirm this as a completely new species, Aspergillus felis, which can cause virulent disease in humans and cats by infecting their respiratory tract," Barrs said. "We were able to demonstrate that this was a new species of fungus on a molecular and reproductive level and in terms of its form."

Barrs said Aspergillus felis can reproduce sexually and asexually, making it similar to the known fungus Aspergillus fumigates.

Since identifying the fungus as a new species, nearly two dozen cats have been diagnosed with Aspergillus felis infection. At least two humans have also been infected with Aspergillus felis, but Barrs notes that the disease cannot be passed between humans and cats.

Aspergillus felis appears to be able to infect otherwise healthy cats. In the two human cases, the infected patients, both of whom reportedly died, already had compromised immune systems prior to infection. So far the disease has only been reported in one dog.

"We are right at the start of recognizing the diseases caused by this fungus in animals and humans. The number of cases may be increasing in frequency or it may just be we are getting better at recognizing them," Barrs said.

She said the similarities between Aspergillus felis and Aspergillus fumigates can cause them to be easily misidentified, especially because cases of Aspergillus fumigates are well-studied in humans.

"However, A. felis is intrinsically more resistant to antifungal drugs than A. fumigatus and this has important implications for therapy and prognosis," Barrs said.

Barrs and her colleagues' research is published in the journal PLOS One.