Nasal Cryptococcosis Caused by Cryptococcus gattii in Sheep in Bahia, Northeastern Brazil

Abstract

Background: Cryptococcosis is a potentially fatal systemic mycosis that can affect several animal species. The disease is caused by the yeast species Cryptococcus neoformans and C. gattii and is usually associated with immunosuppressive diseases or debilitating factors. In Brazil, cryptococcosis in ruminants has been described in several states, but there have been only two instances of infection in sheep. Until the present, cryptococcosis caused by C. gattii has only been reported in goats. The objective of this study was to describe, for the first time, a case of nasal cryptococcosis caused by C. gattiiin a sheep in the state of Bahia.Case: The disease affected a 4-year-old Santa Inês sheep, created in extensive system in the municipality of Ribeira do Pombal, Bahia, Brazil. The animal presented weight loss, with an asymmetric volume increase in the right nasal cavity, accompanied by dyspnea and bloody nasal discharge. Samples of the tumor mass were collected for cytological analysis of yeast structures compatible with Cryptococcus spp. After cytological diagnosis, the sheep was sent to the Livestock Development Center of the Federal University of Bahia. On physical examination, there was a large and firm irregular mass, strongly adhering to the right nasal cavity and causing facial asymmetry. Surgical removal was attempted, but a marked infiltrative character of the lesion was observed, with extensive tissue destruction. Owing to the unfavorable prognosis, euthanasia was carried out followed by necropsy, in which a large irregular mass was observed that almost completely obliterated the right nasal cavity. Resorption of the right nasal bone and the dorsal and middle nasal turbinates was also observed. Fragments of the nasal lesion were collected, fixed in 10% formalin, routinely processed for histopathology, and stained with hematoxylin and eosin (HE) and Mayer's mucicarmine. Samples of this lesion were sent for molecular characterization of the etiologic agent by polymerase chain reaction (PCR). The histopathological evaluation showed hundreds of generally colorless rounded yeasts cells composed of a clear halo, surrounding a slightly basophilic structure, giving the tissue a vacuolated aspect, known as a “soap bubble lesion” There was also intense inflammatory infiltration and extensive areas of necrosis and hemorrhage, which allowed the morphological diagnosis of diffuse granulomatous rhinitis marked with intralesional yeasts compatible with Cryptococcus spp. Additionally, PCR was positive for C. gattii.Discussion: A case of nasal cryptococcosis caused by C. gattii in sheep in the state of Bahia is described for the first time, diagnosed using clinical-epidemiological, cytological, anatomopathological, and molecular data. Airborne infection occurs by inhaling encapsulated spores present in organic matter, such as decomposing vegetables and bird and bat excreta as observed on the farm where the outbreak occurred. It is important to highlight that sheep and goats affected by cryptococcosis can contaminate the environment, and it is prudent to consider animals with the disease as a risk to public health and eliminate them from the herd, given the costs of the few therapeutic options available on the market. It should be noted that in cases of tumor lesions, which are common in cryptococcosis, cytological examination should be recommended, mainly for screening and distinguishing neoplastic and inflammatory lesions. However, anatomopathological and molecular evaluations are essential for the differential diagnosis of other mycotic rhinitis, in particular,  conidiobolomycosis and nasal pythiosis.