A potentially deadly strain of airborne fungus is spreading in the Pacific Northwest and British Columbia. The airborne fungus, Cryptococcus gattii, was previously seen primarily in cats, and in immunocompromised humans, such as transplant and AIDS patients. However the new strain, VGIIc, is a mutation that can infect healthy people and animals, including cats and dogs, and there has been one case in a sheep.
VGIIc appears to be unusually virulent and much more deadly than other Cryptococci, with a mortality rate of almost 25 percent among U.S. human cases analyzed.
Symptoms may appear weeks or even months after exposure. In people, Cryptococcus infection usually starts in the lungs from inhaling fungus particles. It may spread via blood, and can cause meningitis as well as “cryptococcomas,” masses of fungus, that can appear in the brain or other areas. Symptoms include a persistent dry cough, sharp chest pain, shortness of breath, headache, fever, night sweats and weight loss.
In cats, signs are initially seen in the upper respiratory tract, such as a runny nose; but may advance to breathing problems, nervous system problems, and nodules, especially around the sinuses. Treatment with newer anti-fungal drugs is ineffective; the drugs being used to combat it include long-term ketoconazole and amphoteracin, both of which can have significant side effects.
Historically, Cryptococcus gattii is the most common systemic fungal infection in cats, and is more common in cats infected with Feline Leukemia Virus (FeLV) or Feline Immunodeficiency Virus (FIV, also known as “feline AIDS”). In cats, the fungus is invasive and destructive, and can cause ulceration, facial and nasal swelling, and neurological signs.
Cryptococcus is strongly associated with pigeon feces (guano), and recent evidence suggests it also grows in decaying plant matter in hollows of certain trees. As the guano or other matter dries out, the fungas becomes airborne, and if inhaled, can cause infection. Cryptococci may remain viable for at least two years in accumulations of pigeon guano that are protected from drying or sunlight–the exact conditions found in pigeon lofts.
The new strain first appeared on Vancouver Island in 1999, and has been gradually spreading. It is expected to expand into northern California, and possibly further. Freezing kills the fungus, but scientists think that climate change may be helping it spread.
In cats, preventing Cryptococcus can be accomplished by keeping them indoors or in a secure outdoor enclosure, to eliminate exposure to FeLV or FIV, as well as to pigeons, particularly in temperate climates.