Cats Carry Zoonotic Fungal Disease Into a Brazilian Amazon City for the First Time

In a municipality of the Eastern Amazon where feline sporotrichosis had never before been officially recorded, an observational and longitudinal epidemiological study conducted between January 2023 and August 2024 confirmed the disease in 20 of 23 suspected cats in Castanhal, in the interior of the state of Pará, Brazil. The investigation, carried out in partnership with the municipal Zoonosis Control Center, documented a cluster of cases concentrated in a short period, an outcome the authors interpret as evidence of the disease’s emergence in the region and a warning signal for public health surveillance. All of the animals evaluated presented suggestive clinical signs and lesions, and every confirmed case was verified through fungal culture, the confirmatory diagnostic method used throughout the study.

Sporotrichosis is a zoonotic implantation mycosis caused by dimorphic fungi of the genus Sporothrix. In the environment these organisms exist in a mycelial form, but within a host, or when cultivated at temperatures of 35 to 37 degrees Celsius, they switch to a yeast-like morphology. Transmission occurs through traumatic inoculation of the fungus and may involve several routes, including sapronotic transmission from contaminated soil, plants, and organic matter; zoonotic transmission mainly associated with infected felines; and, less frequently, contaminated fomites. Among the pathogenic clade of Sporothrix species, which includes S. schenckii, S. brasiliensis, S. globosa, and S. luriei, S. brasiliensis shows the highest incidence in Brazil, where the disease is currently considered a neglected and endemic mycosis. While sapronotic transmission predominates in most regions of the world, Brazil has experienced a large zoonotic epidemic associated with feline transmission that has contributed to the geographic expansion of the disease.

Felines are the animals most affected by sporotrichosis and also act as reservoirs and disseminators of the fungus to other animals and humans. The behavioral habits of cats largely explain this higher prevalence. Transmission of the fungus mainly occurs through traumatic inoculation caused by scratches and bites from infected felines during territorial or mating disputes, but it may also occur through direct contact with exudates from lesions and contaminated environmental surfaces. Non-neutered males, whether free-ranging or domiciled with outdoor access, play a significant role in the spread of the disease, a pattern the authors also observed in their own data, which included six females and fourteen males among the evaluated animals.

The study relied on the municipal Zoonosis Control Center to identify, register, and notify suspected cases and to collect samples. Agents recorded each animal’s history and physical examination on specific forms, along with epidemiological data covering age, sex, breed, neutering status, behavioral habits, immune status, and demographics. Inclusion criteria required characteristic lesions raising suspicion of subcutaneous mycosis, mainly on the face, paws, and ear tips, together with a history of trauma resulting from fights or contact with other animals also suspected of infection. Clinical specimens were obtained from secretions and ulcerated lesions using sterile swabs in Stuart transport medium for fungal culture, in addition to imprint cytology on glass slides for direct examination. Samples were stored under refrigeration and sent to the Laboratory of Microbiology and Immunology of the Institute of Veterinary Medicine at UFPA–Castanhal, where they were processed within 24 hours of collection.

Diagnostic confirmation followed a defined laboratory pathway. Imprint slides were stained with hematological reagents to visualize characteristic yeast-like cells, and samples were cultured on Mycosel agar, incubated for up to one month and examined twice a week. Fungal dimorphism was evaluated by subculturing isolates on Brain Heart Infusion agar at 37 degrees Celsius, while primary isolation and observation of the filamentous form took place at 25 degrees Celsius. Colonies were assessed for type, size, margins, relief, texture, and pigmentation, and fragments were stained with Lactophenol Cotton Blue for microscopic examination of hyphae and reproductive structures. Animals were considered confirmed cases when compatible clinical findings and characteristic yeast-like cells were observed, with fungal culture serving as the confirmatory method.

Follow-up information revealed a stark outcome pattern: 18 of the 20 confirmed cases progressed to euthanasia, whereas only two animals survived. Most euthanized animals had presented multiple or disseminated lesions, while the two survivors received clinical management and follow-up. The authors report that the surviving animals were diagnosed comparatively earlier and received appropriate veterinary care, reinforcing the importance of timely diagnosis and treatment for improving clinical outcomes. In contrast, most of the remaining animals did not complete or receive antifungal therapy because of the advanced stage of disease at presentation, financial constraints faced by owners, or concerns regarding zoonotic transmission, leading in many cases to euthanasia as the most feasible management option. No specific age range of higher disease occurrence was identified, with ages ranging from 5 months to 7 years; among animals with age information available, the median age was 4.5 years for females and 3.5 years for males.

The pattern of lesions was consistent with previous reports in the literature: the face, primarily the snout and ear tips, was the site of highest lesion incidence, as these areas are most frequently involved in fungal inoculation. Animals with multiple and disseminated lesions exhibited more severe conditions, frequently resulting in death. The dissemination of lesions beyond the site of inoculation is associated with involvement of other organs, such as the respiratory system, leading to inappetence, apathy, and progressive weight loss, and the greater the number of lesions, the higher the fungal load and the risk of transmission to other animals and humans. Spatial analysis showed that confirmed cases were distributed across several neighborhoods of the municipality, with a predominance in peripheral areas, where access to basic sanitation and sanitary surveillance programs is limited and where rudimentary vegetation, recently deforested soils, and sites of improper waste disposal may favor environmental conditions associated with the persistence and spread of infectious agents.

All evaluated animals, both positive and negative, had street access, with extensive roaming in outdoor environments, mainly in recently occupied suburban areas featuring unoccupied lots, residual forest, and abundant organic matter in the peridomestic area. Of the 20 positive animals, 15 were semi-domiciled and five were stray. Beyond the animal findings, the study documented two situations in which zoonotic transmission was possible. In one household with four cats, all later confirmed positive, an adult male owner was bitten on the phalanges by a semi-domiciled cat in his possession and was advised to seek medical care for human diagnosis. In the second case, a female owner sheltering a cat positive for sporotrichosis was bitten on the hand and scratched on the face; characteristic lesions subsequently emerged and disseminated from her fingers to the upper limb and face, and she was diagnosed and treated appropriately. However, these human cases were not investigated as part of the study itself, and no laboratory results, treatment records, or clinical outcome data for the two individuals were available to the authors.

Current recommendations for feline sporotrichosis are based primarily on prolonged antifungal therapy, with itraconazole considered the main treatment option, often administered alone or in combination with potassium iodide depending on clinical presentation and severity. Treatment generally requires several months of continuous administration, regular veterinary follow-up, and monitoring for potential adverse effects, and access to treatment remains an important challenge in many regions because prolonged therapy and repeated clinical evaluations may result in substantial financial costs for owners. In municipalities where public treatment programs are unavailable, these barriers may contribute to treatment abandonment, delayed intervention, or euthanasia of severely affected animals, although some Brazilian states have implemented public initiatives providing diagnosis and treatment free of charge. For human cutaneous and lymphocutaneous sporotrichosis, itraconazole is considered the treatment of choice, with reported response rates ranging from 80 to 100 percent under current guidelines.

The authors note important limitations. Species-level identification was not performed; the diagnosis rested on phenotypic characterization of Sporothrix spp., including direct examination, culture, and fungal dimorphism. Although S. brasiliensis is considered the most likely species given its recognized predominance in the emergence of feline sporotrichosis in Brazil and previous reports from Pará, its involvement could not be confirmed in this study. The relatively small number of confirmed cases and the descriptive nature of the epidemiological data also limited inferential statistical analysis, so the findings should be interpreted primarily as a descriptive characterization of the disease’s emergence in the municipality. The municipality of Castanhal had no history of sporotrichosis notifications at the Zoonosis Control Center, and the high number of cases diagnosed in a short period suggests previous underreporting, especially considering the number of affected stray animals. The authors argue that educational campaigns, professional training for early recognition and diagnosis, improved access to diagnostics, responsible ownership practices, neutering programs, control of stray animal populations, and early treatment of infected animals are important measures to reduce transmission, and that epidemiological studies such as this one provide essential baseline information for surveillance systems and for prevention, monitoring, and control policies in newly affected areas.

Subject of Research: Emergence of feline sporotrichosis with zoonotic transmission risk in Castanhal, Pará, Brazil

Article Title: Emergence of feline sporotrichosis with zoonotic risk in a municipality of the Eastern Amazon, Brazil

Article References: de Sousa, P. F. M., Sodré, G. S., Senado, R. M., da Silva Filho, J. R., da Costa, S. S., de Araújo, B. T. S., Roos, T. B., Pereira, D. I. B., & Lima, J. S. (2026). Emergence of feline sporotrichosis with zoonotic risk in a municipality of the Eastern Amazon, Brazil. Companion Animal Health and Genetics, 13(1), Article 7. https://doi.org/10.1186/s40575-026-00156-3

Image Credits: AI Generated

DOI: 10.1186/s40575-026-00156-3

Keywords: feline sporotrichosis, Sporothrix, zoonotic disease, cats, Brazil, Eastern Amazon, mycology, One Health, public health, euthanasia, stray animals, emerging disease