Cryptococcosis is a fungal infection caused by the environmental yeast, Cryptococcus, which can either be localized or systemic. This fungus thrives in bird droppings and decaying vegetation, commonly associated with Eucalyptus trees. While it is prevalent worldwide, certain regions, such as southern California, Canada, and Australia, are more susceptible to the fungus.
The infection is contracted through a dog’s nasal passages and can subsequently spread to the brain, eyes, lungs, and other tissues. Although rare in dogs, both dogs and cats can be affected by this condition. The symptoms vary depending on the organ systems affected, with animals exhibiting a history of issues over weeks or months, lethargy, and, in less than 50 percent of cases, a mild fever. Additional symptoms may include:
- Nervous system signs such as seizures, wobbly, uncoordinated, or “drunken” movements, weakness, and blindness.
- Skin ulceration.
- Enlarged lymph nodes.
- Vomiting and diarrhea.
- Lack of appetite.
- Nasal discharge.
Causes
The Cryptococcus yeast typically enters the body through inhalation via the nasal passages. In rare cases, these organisms may travel to the terminal airways, although this occurrence is uncommon. Additionally, the yeast can infect the stomach and intestines by entering through the gastrointestinal tract.
Diagnosis
Your veterinarian will diagnose the condition based on the results of the following tests:
- Sampling from the nasal passages, or a biopsy from the bumpy tissue protruding from the nasal passages; flushing the nose with saline may help dislodge infected tissue.
- Biopsy of skin lesions on the head.
- Aspirates from affected lymph nodes.
- Blood and urine cultures.
- Blood tests to identify the presence of Cryptococcus antigens.
- If your dog displays symptoms of neurological disease, a spinal tap and examination of cells will be necessary.
Treatment
If your animal exhibits any signs of nervous system involvement, inpatient supportive care may be necessary. Outpatient care is typically sufficient when the dog’s condition is stable.
Surgery is advised if the dog has nodular (granulomatous) masses in its nose and throat. Removing these masses can alleviate breathing difficulties.
Living and Management
- Monitor liver enzymes monthly in dogs receiving antifungal drugs through regular blood work.
- Improvement in clinical signs, resolution of lesions, enhanced well-being, and regained appetite indicate a positive response to treatment.
- Conduct blood tests to detect the presence of Cryptococcus antigens.
- The expected duration of treatment ranges from three months to one year. Patients with central nervous system disease may require lifelong maintenance treatment.
- Measure the presence of Cryptococcus antigens every two months, and continue monitoring until six months after treatment completion or until the antigen is no longer detectable.
- If the patient maintains low titers for several months after all signs of disease have resolved, continue treatment for at least three more months.
- If titers suddenly increase after treatment, resume therapy promptly.
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