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Published: Jul 27, 2012

As the summer heats up, more cats are going outside and exploring their surroundings. However, this can come with some hidden dangers that owners should be aware of. One such danger is the Aspergillus fungus, a type of mold that can cause the disease aspergillosis in cats.

There are many types of Aspergillus mold, although not all are harmful to cats. Typically, a cat that breathes in the spores of Aspergillus will be able to combat the fungi through their normal immune system. There are numerous protective mechanisms that prevent these spores from reaching the lungs, such as the mucus and cilia lining the walls of a cat’s respiratory tract.

However, cats with a suppressed immune system, or those suffering from asthma or lung disease, may be more susceptible to Aspergillus spores, putting them at a greater risk for aspergillosis. The clinical signs and treatment will depend on where the fungus settles in the body.

Nasal aspergillosis is the most common form of the disease diagnosed in cats, and can cause serious issues with the cat's nose. It's possible for the fungus to erode the small and delicate sinus bones located in the cat's nose. This will likely result in a nasal discharge, typically localized to one nostril. A foul-smelling mucus coming from the cat's nose is very common during aspergillosis, and may last for several weeks. Intermittent nosebleeds are also sometimes recorded.  Nasal aspergillosis is easy to confuse with other upper respiratory infection in cats, so it is important for pet owners to take the animal in to a veterinarian in order to get an accurate diagnose and treatment.

Unfortunately, not all cases of aspergillosis remain in the nose. In rare instances, the spores can travel through the respiratory system and even enter the bloodstream, moving on to other organs, in what is known as systemic aspergillosis. In these situations, the issue can cause damage to any part of the body that it travels to. Anti-fungal medications are available, but they can have significant side effects on important organs such as the kidneys and a cat must be monitored carefully while taking these medications. Generally, the prognosis for a cat with this kind of aspergillosis is not good, although it can be survived if caught early and no major parts of the body have been irreparably damaged.

Ultimately, pet owners should not concern themselves too much with aspergillosis, as it is relatively rare and usually prevented by a healthy immune system. However, owners should still keep their cats away from mold or fungus of any kind, especially if the cat suffers from respiratory problems or has a weakened immune system.