Cats with central nervous system cryptococcosis

Abstract

Background: Cryptococcosis is a serious fungal infection contracted by humans and animals, and the most common systemic mycosis found in cats. This disease is often contracted through inhalation of fungal propagules. The Central Nervous System (CNS) may be infected through local extension (nasal and frontal sinuses) or via hematogenous route. Similarly to CNS bacterial infection, the clinical signs of neurological dysfunction may be attributed to mass effect (gelatinous mass of fungal microorganisms and fungal granuloma formation) or to a more disseminated inflammatory response to invading microorganisms. The objective of this study is to report one case of a patient with cryptococcal granulomas in the central nervous system and one case of a patient with neurological signs associated to a cryptococcosis. Cases: Case 1. A 3-year-old male mixed breed feline was admitted to a veterinary clinic, located in Porto Alegre, RS, Southern Brazil. The patient presented unsourced behavioral changes, vestibular ataxia and dysphagia caused by inability of coordination. The following tests were performed: complete blood count test, biochemical analysis, computed tomography scan (CT scan), fluid analysis, radiography and toxoplasmosis test. The following medicine were administrated for treatment: fluconazole, dexamethasone, mannitol, phenobarbital and levetiracetam. Fluid therapy was also part of the treatment. Immediately after death, the cat was submitted for necropsy, and a fungal granulomatous meningoencephalomyelitis was diagnosed. Cryptococcus sp. was identified as the causal agent through pathological findings, fungal culture and PCR analysis. Case 2. One year later, another feline was admitted to the same clinic (a 2-year-old female mixed breed) presenting hypersalivation, tremors and excessive vocalization. The patient had contact with the deceased feline. The following tests were performed: complete blood count test, biochemical analysis, computed tomography scan (CT scan), cerebrospinal fluid analysis, and radiography. The following drugs were administrated for treatment: fluconazole, prednisolone, phenobarbital, potassium citrate and cefalotine. This patient is frequently monitored by a veterinarian and presents adequate health conditions after the occurrence. Cryptococcus sp. was identified as the causal agent through fungal culture and cytology (cerebrospinal fluid). Discussion: Cats are the most frequently infected animals with the involvement of the upper and or lower respiratory tract, subcutaneous granuloma, and disseminated infections. These animals present a higher quality of life when the disease is diagnosed and treated early. Peripheral enhancement of intracranial cryptococcal granulomas has been demonstrated in felines. These fungal granulomas often present evidence of significant perilesional edema. The most substantial evidence for diagnosis of cryptococcosis is the identification of the microorganism in Cerebrospinal fluid (CSF) samples. The mechanism of the lesion is cellular death, probably caused by secondary atrophy from distortion and tissue compression due to the expansion of Cryptococcus cysts in the cerebral parenchyma. There are several reports of long-lasting remission or cure of CNS cryptococcosis treated with drug combinations, including flucytosine and/or triazole antifungal agents (itraconazole and fluconazole.) The isolated use of flucytosine may contribute to development of drug resistance. One controversial alternative that may be beneficial to the patient is the administration of low prednisolone doses in order to avoid perilesional edema in the initial stages of treatment. The utilization of glucocorticoids after diagnosis was associated to higher survival rates in animals.