Blastomycosis (Systemic Fungal Infection)

Blastomycosis is a systemic fungal infection that, while uncommon in cats, can be extremely serious. It begins when a cat inhales the spores of Blastomyces, a fungus that grows in moist, acidic soil and decaying wood in particular parts of the world, often around rivers and lakes. The spores are too small to see, and simply disturbing contaminated soil can release them into the air to be breathed in.

Once in the lungs the fungus establishes an infection that frequently causes coughing, rapid or laboured breathing and a stubborn fever, and from there it can spread through the bloodstream to distant sites. The eyes are a common target, where infection causes inflammation, cloudiness and sometimes sudden blindness; the skin may develop lumps and draining sores; and the bones, brain and other organs can be affected too. Because the early signs — fever, poor appetite, weight loss and breathing trouble — resemble so many other illnesses and do not improve with routine antibiotics, the diagnosis is easily missed unless the fungus is specifically looked for.

Vets confirm it by finding the organism in samples from affected tissue or fluid, supported by chest imaging and specialised urine or blood tests. Treatment is a long haul: months of antifungal medication, careful monitoring of the liver, and supportive care for cats struggling to breathe. The outlook depends heavily on how early treatment starts and how much of the body is involved — cats caught early can recover well, while those with widespread disease or severe lung involvement have a more guarded prognosis. Reassuringly, the infection is acquired from the environment rather than passed between animals or from cats to their owners through everyday contact.