Cryptococcus Infection

Cryptococcus is the most common fungal disease seen in cats on the Eastern coast of Australia. Luckily it is a rare disease, that is not contagious (i.e. cannot spread between cats or to people). Cats normally will become infected through breathing in the fungi from the environment. Eucalyptus leaves and pigeon droppings are risk factors.

Cryptococcus can cause disease in different ways, but more commonly affects the nose, brain and skin. Very rarely it can occur throughout the whole body. Signs may include lumpy growths over the bridge of the nose, ulcerations, sneezing sometimes with blood, blindness or other neurological signs.

This cat demonstrates numerous skin nodules filled with cryptococcus organisms.

This is an MRI image from a cat with cryptococcus in his lymph node.

Cage side blood tests (Cryptococcus Immy tests) can help increase the index of suspicion for infection if positive but need to be confirmed with another blood test (Cryptococcus LCAT) or by seeing the fungal organism within tissues by fine needle aspirate or biopsy.

This is an image from a sample from a nodule. The large purple circles surrounded by clear discs are cryptococcus fungi.

This image shows changes to the back of a cat's eye (fundus) examined with a special camera that shows dark circular areas of retinal degeneration typical of cryptococcus infection.

Treatment typically involves surgical removal of nodules in the skin or nose if possible and the use of long term (often for more than 12 months) anti-fungal medications. Anti-fungal medications include drugs such as fluconazole, flucytosine and amphotericin B amongst others. The choice of drug is based on the extent of disease and if there are any kidney, liver or neurological (brain) problems.

The prognosis is generally favorable, if the diagnosis is obtained early, although a long course of treatment (months) and follow-up (years) is required. Patients can have relapse of infection. Cats with neurological signs (e.g. blindness, seizures, wobbly gait) have a more guarded prognosis. Animals that survive the first 2 weeks of therapy have a reasonable, but guarded, prognosis.

Cats often exhibit a rapid improvement in clinical signs during the first month of therapy, however it is very important not to stop treatment.

Cryptococcus Infection

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