Milo is an 11 year old domestic shorthair cat with a history of asthma, who is on chronic prednisone therapy to keep his respiratory symptoms controlled. He was seen in the summer for upper respiratory congestion and sneezing. He received two different courses of antibiotics, but his symptoms did not improve.
After the second antibiotic failed, I recommended that we anesthetize Milo and take radiographs of his skull and flush his nasal passages. My rule outs included a polyp, tumor, resistant bacterial infection, fungal infection, or a foreign body (Milo does go outside so he could have gotten a grass blade or seed up his nose).
Milo was anesthetized and his radiographs did show a soft tissue “mass effect” in his nasopharynx. Flushing the nose retrieved some mucus which on microscopic exam showed encapsulated fungal elements. These were consistent with a fungus called cryptococcus.
The slides were sent to the lab for confirmation and we drew blood to check for cryptococcus antigen in Milo’s blood. This came back with a highly positive titer, so we had our diagnosis. Milo was started on an oral antifungal medication and is currently symptom free. He will need to be on long-term medication until his titers show no detectable fungus.
Cryptococcosis is a fungal disease caused by dimorphic fungus of the genus Cryptococcus, which can exist as a spore and a yeast form. The disease is usually contracted by inhaling spores or dried yeast cells. In the United States, the most common form of the disease is caused by Cryptococcus neoformans, and is found in immunocompromised individuals.
In the past 11 years a related fungus, Cryptococcus gattii, has been causing disease in humans and animals in the Pacific Northwest. The organism lives in the soil and is associated with evergreen trees. In humans the disease may present with respiratory symptoms, but the fungus can also invade the central nervous system and cause neurological disease. In dogs and cats, the most common signs are upper respiratory (often with swelling of the nose in cats), neurological, or cutaneous. Whereas Cryptococcus neoformans is typically seen in patients with immune suppression (especially those with HIV), Cryptococcus gattii affects patients with normal immune systems.
Treatment for cryptococcus is usually prolonged, sometimes life-long. For nasal and cutaneous forms, an oral medication called fluconazole is often the sole treatment. For cryptococcus in the central nervous system, injectable antifungals are usually needed, and the prognosis is guarded.
With Milo, we don’t know if his crypto is neoformans or gattii. He is on prednisone, which can reduce immunity, so he may have the neoformans type. The treatment is the same in any case. I have to admit that cryptococcus was not at the top of my list when I went looking for a reason for Milo’s symptoms, but this case shows that it should always be a consideration.
Who should be tested for cryptococcus? Any patient with unexplained central neurological disease, patients with upper respiratory disease not responsive to antibiotics, and patients with cutaneous nodules or draining tracts not responsive to appropriate antibiotics. The fungus can be carried on shoes and clothes, so even indoor pets may be at risk.
If you are interested in learning more about this disease, the CDC website has excellent information on both forms of cryptococcosis.