Neurocryptococcosis in dogs and cats: Anatomopathological and fungal morphological aspects in a case series

ABSTRACT: Cryptococcosis is a fungal infection that commonly affects dogs and cats, often manifesting with neurological involvement. This study investigated the neuropathological characteristics of cryptococcosis in nine cats and two dogs submitted to necropsy through gross pathology and histopathological analysis. Clinical history, lesion location, fungal burden, type and intensity of inflammatory infiltrate, lesions in nervous parenchyma, and morphological characteristics of yeast cells were evaluated. Additionally, fungal morphological criteria, such as capsule and yeast wall thickness and budding frequency, were analyzed in each neurolocation. The Alcian blue stain method was utilized to enhance the visualization of yeasts. Debilitating and/or immunosuppressive conditions were described in five cases. Two cats were recently adopted from the streets, and one cat was treated with corticosteroids. One dog had severe cachexia and generalized weakness, and another dog had leukopenia with left shift. Only six cases (54%) had neurological signs. Gross central nervous system (CNS) lesions were found in five cases and appeared as irregular, friable, soft, gelatinous, and grayish masses with distinct borders. The telencephalic cortex and the cerebellum were the most frequently affected CNS locations observed in all cases. The first exhibited a higher fungal burden and a milder inflammatory response than other neurolocations. The cerebellum was also affected in all cases but showed a slightly higher inflammatory response and a lower fungal burden compared to the telencephalic cortices. Additionally, lung involvement was observed in all cases as well. The inflammatory intensity associated with the yeasts in the CNS was predominantly mild to moderate, being severe only in two cases, and the fungal burden was more often moderate or severe, being mild in only two cases. The observed heterogeneity in the inflammatory response and fungal burden reveals the complex nature of this infection. Other affected nervous tissues were the optic nerve, the spinal cord nerve roots and the ganglia, mostly in cats. In conclusion, our study shows the neuropathological features of cryptococcosis in a case series in cats and dogs, emphasizing the importance of considering specific neurolocations to diagnose this fungal infection and contributing to a better understanding of the simultaneous involvement of the respiratory and nervous systems.