Cryptococcus in British Columbia
Cryptococcus is a fungus that typically lives in the soil and on plant material, but can infect animals and humans. Until recently, clinical infections were rarely diagnosed in this area, but since 2000, we have seen a dramatic increase in the numbers of animals affected on southeastern Vancouver Island.
In particular, a cluster of cases at Rathtrevor Beach generated considerable attention several years ago. There have been well over 500 cases of Cryptococcus in animals on Vancouver Island (Since 2000), with more than 150 cases diagnosed here in Victoria. Cats are more commonly affected than dogs, and it is interesting to note that we have diagnosed Cryptococcus in strictly indoor, as well as outdoor cats. Most clinical infections on Vancouver Island are caused by Cryptococcus gattii.
Infection usually results from inhalation of the fungal spores into the nasal passages. From there, Cryptococcus can then spread to other areas of the body. It is not transmissable from animals to humans or vice versa. While the respiratory system is commonly the first to be involved, Cryptococcus can affect almost any organ including the brain, sinuses, intestinal tract, skin, and eyes. Clinical signs are extremely variable, depending on which parts of the body are infected, and take at least 5 to 6 months to develop after infection. Symptoms include loss of balance, lethargy, inappetence, sneezing, nasal discharge, skin nodules, dilated pupils, vision loss, weight loss, vomiting, diarrhea, and generally doing poorly.
Tests for Cryptococcus include blood testing (antigen titres) and microscopic analysis of samples taken from affected areas (cytology).
There are several medications available to treat Cryptococcus. Initially, we typically use an oral antifungal medication such as itraconazole, ketoconazole, or fluconazole. These medications are relatively tasteless, and are absorbed better if given with food, so we recommend giving them with a meal. Patients often start to improve within days of starting treatment. Antifungal medications are relatively expensive and usually have to be given for 6 months or more. During this time, we recommend monitoring patients periodically with blood tests for two reasons: first to minimize the risk of side effects from the medication (such as kidney or liver damage), and secondly to monitor the antigen titre so we can determine the effectiveness of the treatment.
In most cases, antifunal medications are good at controlling symptoms, but may fail to completely eliminate crypto from the body...
In most cases, antifungal medications are good at controlling the symptoms, but may fail to completely eliminate the Crypto from the body. In this case, surgically removing skin nodules once patients are stabilized is recommended. Another option is amphotericin B, an injectable medication that has a stronger effect and can be used in conjunction with the oral medications to help get eliminate the fungus from the body. In general, we recommend treating for 1 to 2 months after all symptoms have cleared and the Cryptococcus tests are negative. Response to treatment is generally positive, although once the organism has entered the nervous system, it is much more challenging to treat successfully, especially if signs are severe. Often it is necessary to constantly treat pets with a corticosteroids to improve neurological signs.