Feline cryptococcosis is the systemic disease caused by fungi most frequent in cats, however, its incidence in the feline population is short. Cryptococcosis occurs more frequently in the nasal area, showing a swelling that can sometimes become very obvious, due to the development of a fungal granuloma. Other times, cryptococcosis affects the lungs, eyes, nervous system or systemically, when it occurs in various areas of the body when distributed by hematogenous or lymphatic routes. Treatment is based on the use of therapy aimed at specifically killing the yeast, and sometimes resection of the fungal granuloma in the cat is also performed.
In this article on our site we will talk about cryptococcosis in cats, its symptoms and treatment, so you can better understand this very common disease and learn to identify it.
What is feline cryptococcosis?
Feline cryptococcosis is an infectious disease that affects cats and is caused by fungi, specifically the most frequently isolated fungal agent es Cryptococcus neoformans, being a disease associated with habitats where there are birds, especially pigeons, because it is found in their feces. It can also be caused by Cryptococcus gattii, generally in tropical or subtropical climates, and the source of infection is the plant matter of certain trees.
This is a small-sized yeast distributed throughout the world. It has a capsule, which in addition to protecting it from drying out, makes it difficult for the cat's immune system to recognize it and trigger the immune response necessary for its elimination. However, it is a disease with a low incidence.
In cats, a risk factor for the development of C. neoformans cryptococcosis is the presence of immunosuppressive diseases such as feline leukemia or feline immunodeficiency. However, C. gattii infection can occur in individuals without immune system involvement. However, in immunocompromised individuals the infection is usually more severe, while in those with a strong immune system the infection is usually located in the nasal area, without spreading.
What is the pathogenesis of cryptococcosis?
The main source of infection is inhalation of yeasts, depositing in the upper respiratory tract where they produce nasal granulomas. If they reach the lower lung passageways, they cause granulomas in the lung.
The fungus can spread to other places, such as the central nervous system by blood, lymphatic route or by local invasion through the cribriform plate of the ethmoid bone that connects the brain with the nasal cavity. They can also reach other locations, such as the eyes, face, and skin. If a severe systemic form of the disease occurs, the yeast can spread to organs such as the spleen, heart, kidneys, digestive organs, muscle, or lymph nodes.
Symptoms of cryptococcosis in cats
Cryptococcosis can give rise to very different clinical signs depending on the location of the yeast and its degree of dissemination. There can be several types of cryptococcosis in cats: nasal, pulmonary, nervous, ocular, and systemic.
Nasal cryptococcosis
In nasal cryptococcosis in cats, the most common symptoms are respiratory, with the most frequent being signs of the upper respiratory tract such as:
- Unilateral or bilateral mucopurulent or bloody nasal discharge.
- Rhinitis.
- Nasal swelling.
- Granulomas.
- Sneezing.
- Respiratory rales.
- Pain.
- Respiratory difficulty.
Pulmonary cryptococcosis
When the yeast affects the lungs, granulomas are produced, foci of pneumonia and infiltrates around the bronchi that will produce signs of lower airways What:
- Cough.
- Respiratory difficulty.
- Fever.
- Lung sounds.
Cryptococcosis Nervosa
Cryptococcosis can also reach the nervous system, where you can see nervous signs that may be a consequence of encephalitis or meningitis due to presence of yeast in the central nervous system, such as:
- Pupillary dilation (mydriasis).
- Gait disturbance.
- Incoordination.
- Indifference.
- Total or partial blindness.
Ocular cryptococcosis
When the yeast targets the eye, it produces:
- Optic nerve neuritis.
- Chorioretinitis.
- Mydriasis.
Systemic cryptococcosis
When cryptococcosis affects various locations, multiple symptoms may occur, being the most serious form of the disease. Among them, these symptoms stand out:
- Fever.
- Cough.
- Lung condensation.
- Anorexy.
- Weightloss.
- Weakness.
- Ataxia.
- Mucosal ulcers.
- Lameness.
- Vomiting.
- Diarrhea.
- Cutaneous granulomas.
- Increased lymph nodes.
Diagnosis of cryptococcosis in cats
The diagnosis is made, in addition to the clinical signs and the animal's clinical history, by laboratory and complementary tests, among them the isolation and identification of the microorganism by cytology and culture, as well as the determination of the yeast capsule antigen. We detail these tests:
- The cytology is performed by puncturing affected areas, such as lymph nodes, masses in the nasal area or skin. Subsequently, it is observed under a microscope with a stain, such as Gram, methylene blue, Wright and India ink, to visualize the organism. It is an easy organism to detect due to its characteristic polysaccharide capsule.
- The culture is performed from samples of cerebrospinal fluid or exudates. Samples should be incubated in Sabouraud agar medium or blood agar, at a temperature between 25 and 35 ºC. After 36-72 hours, in the case of being positive, bright cream-white colonies will appear. Colonies of C. neoformans are less mucous than those of C. gattii. To detect the yeast, the capsule must be visualized and its biochemical characteristics confirmed, such as the ability to reduce nitrates to nitrites and the ability to hydrolyze urea.
- To detect the antigen of the capsule, the latex agglutination test or ELISA is performed, with samples of blood serum, liquid cerebrospinal fluid or urine. This test has a high sensitivity and specificity in the cat.
Chest X-ray can be useful in the case of pulmonary cryptococcosis to visualize pulmonary and bronchial alterations.
Feline cryptococcosis treatment
The therapeutic protocol for cryptococcosis includes treatment with antifungals to kill the yeast and surgical resection of the granulomas. surgical resection is performed in cats with granulomas in the nasal cavity as a complement to medical treatment with antifungals.
The most commonly used antifungals for the treatment of feline cryptococcosis are:
- Fluconazole: it is the antibiotic of choice today because it is the most effective and safest. A dose of 50 mg/12 hours orally is used. It is also effective in case of nerve infections by crossing the blood-brain barrier.
- Itraconazole: Also effective like fluconazole, but can be toxic to the liver.
- Ketoconazole: It is effective, but it is not useful in cryptococcosis nervosa and can cause side effects such as vomiting and loss of appetite in the cats.
- Amphotericin B with 5-fluorocytosine is a very useful treatment when there are nervous signs. It was used more a few years ago.
In any case, it is important to go to the veterinary clinic so that a professional can confirm the disease and establish the best treatment. Never self-medicate a cat.
