Cryptococcosis in Dogs

The Cryptococcus organism is found mainly in soil and excrement, usually in pigeon guano, and can remain viable for 2 years. Though it primarily affects cats, it can infect dogs, horses, birds, and humans. In dogs, it often begins in the nasal cavity, spreading to the nervous system, then the skin, digestive system, eyes, lymph nodes, bone, muscle, heart and other organs. Treatment should be sought as soon as possible, as once the central nervous system is involved, the chance of recovery is significantly decreased and mortality rates are high.

Cryptococcosis is a systemic fungal disease caused by the Cryptococcus organisms. These are yeast-like fungi that are saprophytic, or organisms that feed on decomposing and dead material. If inhaled or contracted through a wound, the organisms attack the respiratory system first by creating small areas of granulomas, or a collection of immune cells that cause an inflammation. These lesions generally continue through the body, causing upper respiratory disease, mental alterations, loss of movements and seizures.

Symptoms can vary based on the type of cryptococcal organism and the stage of infection. They can include:

• Lesions in the nasal cavity, or a nasal granuloma
• Lesions on nose
• Upper respiratory tract disease
• Lung granuloma
• Subcutaneous masses
• Nasal discharge, containing mucous and pus
• Nose bleeds
• Noisy breathing
• Coughing
• Sneezing
• Meningoencephalitis, or inflammation of the brain and meninges
• Altered mental state
• Changes in behavior
• Loss of body movements
• Pain in neck
• Seizures
• Weight loss
• Anorexia
• Eye lesions
• Eyeball protrusion
• Blindness
• Lesions inside body, affecting various systems

Types 

There have been up to eight distinguishable strains recognized of Cryptococcus, split between c. neoformans and c. gatti. VN I is the type that most commonly infects dogs, and is a type of c. neoformans.

Cryptococcosis is caused by an infection of the Cryptococcus organisms. Infection can happen through:

• Inhalation of Cryptococcus neoformans and gatti organisms
• Contamination of wounds with Cryptococcus neoformans and gatti organisms

Often, respiratory and nervous system issues will lead to a veterinary visit. Be sure to tell your veterinarian all the symptoms you have seen in your dog, as well as the kinds of things your dog has had access to outside, specifically if he has been near a lot of bird droppings. After a full exam, your veterinarian may suspect cryptococcosis.

The quickest diagnosis can be made from a cytologic exam of nasal and skin cells, eye cells, joint fluid, and tissue samples. A stain is used to visualize the organism. If no organisms can be seen, or if the tests give a false negative, a biopsy of a lesion can be tested.

Lesions inside the body can be seen in thoracic X-rays, CT scans, and are often found after death. A latex agglutination test may also be performed to detect the organisms in serum, urine or cerebrospinal fluid. This is often used to determine the success of the intended therapy.

Antifungal drugs are prescribed, sometimes in combination, for 6 to 12 months, and are the main method of treatment. Particular antifungals will be chosen based on the systems affected and the specific strain of organism found, as there are strains that are resistant to certain drugs. Azole drugs are the most commonly used and successful course of treatment. 

Glucocorticoids may also be prescribed when the nervous system is affected, and have been seen to improve survival time if used in the first 10 days. These can help the inflammation and edema in the central nervous system that is caused by dying Cryptococcus organisms. If there is a subcutaneous or internal mass, surgery may be performed to remove it, followed by antifungal therapy.

Recovery is dependent on how far the disease has progressed and if there are any preexisting immunosuppressive conditions. If the central nervous system is affected, the chance of recovery is highly decreased, and death can occur. In one study, 52% of affected dogs were euthanized, or diagnosed after death. 24% of dogs treated were in recovery with 3 to 13 months of treatments.

Your veterinarian may prescribe antifungal medications for home administration, and you may also have future visits to test the effectiveness of the treatments. If surgery was performed, you may need to clean or change bandaging, and administer antibiotics or pain medications.

Contact with your affected dog is not a risk to you or other people. The source of the contamination is the significant health risk. To prevent your dog from contracting the Cryptococcus organism, restrict your dog’s access to any known areas of bird droppings, such as pigeon lofts.