Systemic Cryptococcosis in a Miniature Schnauzer Dog

Abstract

Background: Cryptococcosis is an important zoonotic disease that occurs worldwide. The disease is caused by a soilborne opportunistic fungus of the genus Cryptococcus, which can also be found in the feces of birds, especially pigeons. In Brazil, the geographical distribution of the agent is fairly defined, with the species C. gattii predominantly found in the
north-eastern states. Diagnosis is based on the clinical history, physical examination findings, and results of complementary testing, such as cytopathological and histopathological examinations. This report aims to describe the clinical and anatomopathological findings in a case of systemic cryptococcosis in a dog.
Case: A 4-year-old female Miniature Schnauzer was referred for necropsy. For 3 months prior to death, the dog had displayed generalized alopecia, pruritus, and severe weight loss, Initially, a private veterinarian had suspected leishmaniasis. Gross examination was performed and samples for cytopathology, histopathology, and fungal culture were obtained. The
macroscopic examination revealed generalized alopecia, congested mucosa, cachexia, hyperemia of the brain, and multiple white nodules measuring 0.5 cm to 4 cm in the lungs and the kidneys. None of the other organs showed significant lesions. Cytopathological examination of the nodules revealed a highly cellular sample, with a severe chronic inflammatory response, characterized by multinucleated giant cells and round-to-elliptical, yeast-shaped structures (5-10 μm), suggestive of
Cryptococcus organisms. Histopathological examination of the lungs, kidneys, and brain revealed a severe diffuse chronic inflammatory process, with lymphocytic infiltration and multinucleated giant cells; countless yeast-shaped, round-to-ovoid structures (similar in appearance to “soap bubbles”) that were negative in hematoxylin-eosin stain were also present.
Grocott’s methenamine silver stain was then applied, which positively stained the organism capsules black, confirming Cryptococcus. For mycological diagnosis, samples from the lungs nodules were cultured on Sabouraud’s dextrose agar supplemented with chloramphenicol 0.4% and incubated for 7 days at 25-30ºC. Abundant small, smooth, irregular-sized,
cream-colored colonies were obtained, and a mycological smear, stained by India ink, was performed.
Discussion: Considered an uncommon disease, canine cryptococcosis can be misdiagnosed. Clinical findings, such as alopecia, lymphadenopathy, and cutaneous nodules that may be ulcerated, are commonly seen in these patients due to the hematogenous spread of the organism. In the case described, the dog’s owner was contacted and asked to provide epidemiological information. The owner reported that the dog had lived in an apartment, with little access to the street; however, pigeons were frequently observed on the balcony, along with pigeon feces in the dog feeder. The presence of pigeon feces is a risk factor for the development and spread of the fungus, which may be problematic to public health. Cytopathological examination is a simple, quick diagnostic tool with good sensitivity for some infectious agents. Mycological culture can provide results due to the characteristic of the Cryptococcus sp., since the encapsulated yeast produces a mucous-like colony. Cryptococcosis has a relevant role in public health, so a precise diagnosis is imperative. Its diagnosis is based upon culture, cytology and serological tools. When the animal does not survive to the ilness, the association between necropsy
findings and histopathological examinations is essencial.
Keywords: canine, diagnostic, yeast, anatomopathology.