Introduction

Brazil has a population of 121.3 million dogs and cats, of which approximately 35% live on the streets [1]. These animals, in addition to the suffering they face on the streets, generate socioeconomic and environmental costs and represent a challenge for public health, as they are involved in scratching or biting accidents, predation on wildlife, and transmission of zoonotic diseases, such as sporotrichosis [2,3].

Zoonotic sporotrichosis, primarily transmitted by cats, is predominantly caused in Brazil by Sporothrix brasiliensis, a species recognized for its increased virulence and wide geographic distribution [4–7]. Over recent decades, the disease has expanded substantially, with human cases reported in 25 of the 26 Brazilian states, representing the main endemic areas and clinical presentations of the infection [8]. Between 1907 and 2020, a total of 10,400 human cases and 8,538 animal cases were documented, of which 7,750 (90.77%) occurred in cats and 676 (7.92%) in dogs [9]. Sporotrichosis is currently considered a neglected subcutaneous mycosis with widespread distribution throughout the country, particularly affecting the Southeast and South regions [10,11].

In the state of Minas Gerais, and specifically in its capital, Belo Horizonte, the first cases of zoonotic sporotrichosis were reported in 2015. Since then, the disease has shown a marked increase in incidence, with transmission now documented across all administrative regions of the city and in neighboring municipalities. Between 2018 and 2022, a total of 1,864 human cases were reported in the state, with Belo Horizonte consistently accounting for the highest number of notifications during this period [10].

Sporotrichosis is a public health problem, especially in urban regions with high population density. For its control and prevention, it is necessary to implement multidisciplinary strategies, with approaches that include actions in human, animal and environmental health [5,12,13]. However, despite the growing impact of the disease in Brazil, the country still lacks an effective Surveillance and Control Program for the disease, there are no comprehensive national public policies or standardized protocols to monitor and contain its spread in free-roaming cats populations, which live in public areas, poor communities or are abandoned in institutional spaces, including university campuses.

On university campuses, the availability of resources and the presence of people willing to care for these animals make them recurrent points of abandonment, which generates conflicts within the academic community [14]. As a measure for the management of free-living animals and especially the control of zoonoses, it is necessary to institute ethical and humane population management programs that have One Health as their premise [15,16].

The No-Kill movement, which advocates an end to the euthanasia of animals considered healthy and adoptable, began informally in the United States of America (USA) around the 1930s. However, it was only in the 1990s that this initiative gained greater visibility and strength, progressively expanding to other countries, states and municipalities on the American continent. In Brazil, the movement had its initial milestone with the enactment of Law nº4.808/2006 in the state of Rio de Janeiro, which prohibits the elimination of animals as a method of population control [16]. More recently, Federal Law nº 14.228/2021, which came into force in 2022, prohibits the elimination of dogs and cats in public establishments, except in cases of serious and incurable infectious diseases or those that pose a risk to other animals and public health [17].

Trap-Neuter-Return (TNR) is an ethical population management method widely used to control colonies of free-roaming and feral cats, and is widespread both in Brazil and in other countries [18–22], and is also applied on university campuses [14,23]. It is a non-lethal technique, which consists of collecting, surgically sterilizing, identifying, registering, and returning the animal to the place of capture [16,24], and may include anti-rabies vaccination and complementary tests [25,26].

Considering the growing territorial expansion of sporotrichosis in Brazil, the increase in feral colony populations, and the lack of protocols for disease control and population management, a new approach is required. Although several studies describe the clinical treatment of feline sporotrichosis and its public health implications, there is a gap in the literature regarding the specific management of free-roaming cat colonies affected by the disease. Thus, the present study proposes and evaluates an operational model that integrates animal treatment, population management, and zoonotic risk mitigation, representing the first study of a surveillance and control program for sporotrichosis in free-roaming animals.

Materials & methods

Surveillance and control of sporotrichosis at the UFMG Pampulha Campus

Surveillance of sporotrichosis at UFMG’s Pampulha Campus is carried out according to the flow described above. The animals are monitored in situ by appointed and volunteer caretakers, as well as doorman and security guards who have received prior training. These were responsible for observing and caring for the animals on campus, reporting any new individuals or animals presenting lesions compatible with sporotrichosis to the CPPA.

In suspected cases, animals were captured for confirmatory examination via cytology and/or mycological culture [28]. Sample collection was performed in situ with friendly restraint for approachable animals, or using traps/forceps with sedation at the UFMG Veterinary Hospital for unapproachable ones, always using appropriate PPE. For cytological analysis, smears were stained using a Romanowsky-type method (Rapid Panoptic) [5]. For fungal culture, samples were plated on Mycosel agar and incubated at 25°C, being monitored for 7–30 days to detect the growth of filamentous hyaline colonies [5]. Cases were considered confirmed when the mycological culture was positive or by the observation of yeast structures in the cytological examination. However, for feral animals where capture and sampling were unfeasible, diagnosis was based on clinical–epidemiological criteria. These were defined as the presence of ulcerated, nodular, or exudative skin lesions suggestive of sporotrichosis, occurring in areas with previously confirmed cases.

Samples were collected using sterile swabs, which were carefully rubbed over the selected area and then stored in tubes containing Stuart transport medium for microbiological analysis. At the same time, the swabs were imprinted onto glass slides with a frosted edge, pressing them three times at different points on the ulcerated lesion for cytological analysis. The swabs collected were processed and analyzed at LABIOMIC (Laboratory of Molecular Biology and Mycology) in the Department of Preventive Veterinary Medicine (DMVP) at the UFMG Veterinary School. The cytology slides were processed and interpreted at the Clinical Pathology Laboratory, also at the UFMG Veterinary School. All suspected or confirmed cases were documented and compulsorily notified to the Belo Horizonte Municipal Health Department, even before the obligation was established in 2024 by DAPS Joint Technical Note Nº 011/2024.

Animals that tested positive for fungal culture or cytology were referred for treatment. In all cases, itraconazole was administered at a dose of 100 mg/day, or in combination with potassium iodide at a dose of 2.5 to 5 mg/kg, according to each clinical case [4,5]. The medication was given once a day, in the first meal of the day, along with a small amount of moist food, such as sachets, to optimize absorption and ensure complete ingestion of the medication(s). The rest of the food was then given to each animal. The treatment was maintained until the lesions had completely healed, the hair had grown back and the respiratory signs had ceased, characterizing a clinical cure. After this phase, therapy was extended for a further 30 days to prevent recurrence. In animals with respiratory symptoms and increased nasal volume, treatment was extended for a further 60 days after the clinical cure [5].

The choice of treatment site took into account different factors, such as the animal’s origin, the presence of committed and available carers, the existence of a feeding point, the daily frequency of food provision (Monday to Monday, without an automatic dispenser at the weekend) and the location in areas of risk to the academic community (for example near children’s schools, restaurants or other places with a greater flow of people) (Fig 1). Regardless of the assigned location, the medication was administered orally every 24 hours, offered mixed with a small portion of wet food to facilitate ingestion. The treatment was therefore divided into two groups:

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Fig 1. Flowchart of treatment of animals positive for sporotrichosis at the Pampulha Campus by CPPA- UFMG, 2022 to 2025.

https://doi.org/10.1371/journal.pone.0334204.g001

1. Animals suspected of having sporotrichosis that were abandoned or in the community where it was difficult to standardize feeding or had comorbidities were sent to temporary homes with an isolation area and caregivers trained to administer medication, reducing risks. Preferably, these animals were treated in partner veterinary clinics that had adequate facilities, which also applied to community animals without regular daily sightings or a caregiver responsible for feeding.
2. On the other hand, community animals with established feeding points, dedicated caretakers for daily management, and guaranteed sighting frequency were treated in situ. In these cases, medication administration was strictly supervised to ensure the target animal consumed the full dose without interference. Daily notifications were sent to CPPA-UFMG, including photos of the animal to monitor clinical progression and of the empty feeders after medication administration.

Regarding case management, animals achieving clinical cure, characterized by the complete remission of clinical signs compatible with sporotrichosis followed by maintenance treatment with itraconazole for an additional 30 or 60 days after sign resolution [5], were neutered and subsequently referred to the Trap-Neuter-Return (TNR) program or made available for adoption. Animals presenting therapeutic failure (defined as lack of clinical response to treatment) or concomitant health conditions that hindered recovery were euthanized. These animals, as well as those that progressed to natural death, defined as death occurring during follow-up due to disease complications without human intervention, were sent for necropsy and subsequent incineration by a specialized service at the UFMG Veterinary Hospital. All personnel involved in the handling and care of the animals received guidance on zoonotic sporotrichosis and associated preventive measures.

Results

Origin and spatial distribution of suspected and confirmed sporotrichosis animals

Between January 2020 and January 2025, 23 felines with suspected sporotrichosis lesions were reported in the study area, 11 (47.83%) of which were new (abandoned) animals and 12 (52.17%) community (resident) animals, distributed across 13 (30.23%) of the 43 units. During the same period, one dog was also reported as a suspected case; however, the present study focused on cats, which are currently the main animals involved in the zoonotic transmission of sporotrichosis in Brazil.

There was an association between academic units and the occurrence of abandoned animals with suspected sporotrichosis (p < 0.05). The School of Physical Education, Physiotherapy and Occupational Therapy (EEFFTO) was the only unit demonstrating a significant association with abandoned animals, concentrating 45.5% (5/11) of the cases in this group. Table 1 shows the absolute and relative frequency of notifications, as well as the association analyses by academic unit.

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Table 1. Distribution and association between Academic Units and abandoned and community cats with suspected sporotrichosis on the Pampulha Campus – UFMG (2020-2025).

https://doi.org/10.1371/journal.pone.0334204.t001

CEU (University Sports Center), DGA (Environmental Management Department), DQ (Department of Chemistry), EDM (School of Music), EEFFETO (School of Physical Education, Physiotherapy and Occupational Therapy), EEN (School of Engineering), EMEI (Alaíde Lisboa Municipal Early Childhood Education School), EV (School of Veterinary Medicine), FAFICH (Faculty of Philosophy and Human Sciences), FAO (School of Dentistry), GP (Forte Warehouse) and IMPU (University Press).

A comparison of the frequencies of the clinical, treatment and resolvability variables according to group is shown in Table 2.

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Table 2. Distribution of cats suspected of sporotrichosis according to clinical variables, treatment and resolvability at the Pampulha Campus – UFMG (2020-2025).

https://doi.org/10.1371/journal.pone.0334204.t002

Treatment for sporotrichosis and the outcome of cases

Among the positive animals, 83.33% (10/12) were treated for sporotrichosis and 16.66% (2/12) were not treated due to the presence of comorbidities, specifically chronic kidney disease, trauma-related injuries, or concurrent infectious diseases, and an unfavorable prognosis. As for the fate of the positive animals, 41.66% (5/12) were returned to their place of origin on campus and 25% (3/12) were donated, 16.66% (2/12) were euthanized and 16.66% (2/12) died before treatment was instituted, as they were abandoned on campus in an advanced stage of the disease. The animals that died were sent for necropsy, followed by incineration of the carcasses.

Some variables showed a significant association. All the community animals (residents) were neutered (p-value = 0.000). The prognosis of community animals was more favorable than that of abandoned animals (p-value = 0.012). With regard to the treatment setting, community animals were predominantly treated in situ (p-value = 0.012). In addition, the average treatment time was significantly longer for abandoned animals (p-value = 0.0357), being approximately twice as long as for community animals.

As shown in Fig 2, the community animals were treated for an average of 2.2 months, while the abandoned animals had an average treatment time of 4.8 months.

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Fig 2. Treatment time in months of abandoned and community animals positive for sporotrichosis on the Pampulha Campus – UFMG (2020-2025).

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The final destination of the animals also differed between the groups (p-value = 0.013): while the main destination for abandoned animals was adoption (residual value = 2.083), community animals were mostly returned to their place of origin (residual value = 3.121), as shown in Fig 3.

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Fig 3. Hierarchy map of comparison between groups of the variables reproductive status, prognosis and destination of animals suspected of sporotrichosis on the Pampulha Campus – UFMG (2020-2025).

*Statistical significance was determined using Fisher’s exact test (p-value ≤ 0.05).

https://doi.org/10.1371/journal.pone.0334204.g003

There was no significant association between the variables species, sex, location of the lesion, capture, positivity, criteria for confirming the diagnosis (cytology, culture and clinical-epidemiological), institution of treatment, therapeutic protocol (itraconazole in monotherapy or in combination) and outcome (clinical cure, suspension of treatment, death, euthanasia and relapse), as verified by Fisher’s Exact Test.

Discussion

CPPA-UFMG has set up a monitoring and surveillance network, as well as a solid population management program over the last five years, with stabilization of the resident (community) animal population. Despite this, UFMG still has high abandonment rates [14]. The gates have no entry control during university hours, which allows free movement on campus and corroborates the migration and abandonment of animals.

This scenario may explain why the unit with the highest number of animals suspected of sporotrichosis was the EEFFTO, as it is located at one of the university’s main entrances and lacks constant surveillance, making it easier for animals to be abandoned.

Most of the positive animals were cats and males. These findings are consistent with the cases described in the literature, whose main risk factors for zoonotic sporotrichosis include cats with access to the street, males, not neutered and involved in disputes over territory and females, increasing the likelihood of infection [28–31]. In the present study, the reproductive status variable differed from the literature because most of the animals had already undergone TNR and were fixed. However, the positivity can still be explained by the fact that these animals, in the case of community animals, lead a free life, roaming in open areas, scratching tree trunks [5] and other behavioral factors, contact with other cats and food-related disputes.

For diagnosis, most cases were confirmed by laboratory criteria using cytology and fungal culture, the latter being considered the gold standard test [30,32]. In some cases where sample collection was not possible, a clinical-epidemiological diagnosis was established. This was defined as a suspected case with an epidemiological link, including contact with other cats or confirmed animals, and presence in an area with known transmission. Although not ideal, according to the Ministry of Health, it can be used in endemic areas to prevent the spread of the disease [10].

As for the outcome of the cases, when comparing the groups, although the community animals had a better initial prognosis than the abandoned animals. There was no difference in the percentage of clinical cures comparing the groups. Although there was no correlation in this study between the therapy instituted and the cure, studies have shown that monotherapy with itraconazole has cure rates varying from 38.3% to 100% [8,33] and that in association with potassium iodide the cure rate increases to 88% to 96.15% of cases with an average of 3.5 months of treatment [4,31]. The average treatment time is between 4 and 9 months, and it is necessary to continue the medication after clinical cure [34]. Medication should be maintained for at least one month after remission of clinical signs, and for two months in cases where the respiratory system is involved, to reduce the risk of relapse, characterized by the recurrence of clinical signs after the discontinuation of therapy in animals previously considered clinically cured [5]. In the cases evaluated, the treatment time for each animal varied between one and six months, reflecting the differences in responses to treatment, which are influenced by factors such as the severity of the infection and the individual response of each animal [34]. However, in the group of community animals, it was found that the cure was achieved in half the time when compared to the cure in abandoned animals. This discrepancy is likely attributable to the fact that abandoned animals are often presented with more advanced disease stages and a higher number of lesions, possibly having been abandoned due to the owners’ inability to provide treatment. Additionally, the lack of a human-animal bond hindered immediate capture, delaying the onset of therapy and worsening the clinical picture. Conversely, community animals benefited from conditions similar to domiciled pets, including regular high-quality nutrition, sanitary (vaccination, deworming) and reproductive control, and reduced environmental stress due to the provision of shelter and the care provided by guardians, which likely contributed to a more robust immune response [14].

When the fate of the animals after diagnosis was analyzed, the findings of this study showed that in situ treatment exclusively for resident (community) animals can be an alternative for public health purposes and an alternative to euthanasia for free-living animals, since the treatment time for these animals was shorter than for abandoned individuals and there were no reports of human cases or new animals in the respective animal units. It is extremely important to closely monitor each animal treated in the field, administering the drug in a small amount of food, in the first meal of the day, ensuring complete ingestion and only after giving the rest of the food. Photographing the animals every day to follow their clinical progress and monitoring the other animals in the colony with images are essential. Otherwise, difficulties in confinement can result in irregularities in the administration of medication, which can lead to a recurrence of the disease, hindering the healing process and favoring the spread of Sporothrix [34,35].

The absence of new feline cases in the treated units or human cases shows that the establishment of an effective and viable therapeutic protocol for cats in field conditions is essential for the control of sporotrichosis dissemination among animals, as well as its zoonotic transmission [5]. However, for this protocol to be applied, criteria must be taken into account that depend directly on the commitment of the caregiver and the monitoring of trained professionals, avoiding therapeutic errors and recurrence of the disease [36]. The existence of a fixed feeding point and daily maintenance is fundamental to the success of the action. Itraconazole and potassium iodide capsules can be opened and administered with wet food, provided that the itraconazole beads remain intact [9]. This strategy facilitates administration and significantly reduces the risk of zoonotic transmission by minimizing the need for physical restraint and direct contact with the infected animal [4,5]. In places where there are no caregivers to ensure this, the animals should be collected, especially in cases of abandonment. Volunteer caregivers should receive training on the disease, understanding the risks, prevention measures and the importance of committing to treatment.

According to de Souza et al. [9], when health education actions were implemented for the caretakers of cats affected by sporotrichosis, treatment time was reduced from 131.2 days to 67.5 days, a reduction of 48.55%. These findings highlight the relevance of educational strategies as tools to improve therapeutic efficacy, reducing both treatment time and the risk of abandonment, as well as contributing to the control of sporotrichosis transmission in the context of One Health.

As an associated control and prevention measure, subjecting free-living animals to NRT after clinical cure is essential to reduce the chances of transmission within the colony. Ideally, preventing animals from freely roaming the streets is only feasible through responsible adoption, which in Brazil is not yet a reality due to the high number of animals for few available homes, despite the significant allocation of abandoned animals for adoption observed in the study. For community animals, the return to the unit of origin, combined with continuous monitoring by the community involved, as well as the use of tools such as camera traps for surveillance, is essential to identify possible relapses.

The surveillance and control of sporotrichosis in free-living cats is a constant challenge for public health. Actions need to be continuous, integrated and guided by the One Health concept. The availability of financial, physical and human resources is a determining factor in the creation of public policies and effective guidelines for the control of zoonotic sporotrichosis. In this context, ethical population management programs are fundamental to reducing abandonment and controlling stray populations, as demonstrated by the work of CPPA-UFMG on the Pampulha campus.

The results reinforce the need for an active surveillance network to identify suspected cases early and refer them for diagnosis. In addition, there are viable alternatives to euthanizing feral cats with sporotrichosis, but their implementation depends on the structure and resources available.

Study limitations include the reduced sample size, which reflects the number of sporotrichosis cases identified during the study period and characterizes a convenience sample. Although this sampling strategy may limit the generalizability of the findings, the active and continuous surveillance implemented on campus enabled the timely identification of most cases, ensuring that the data are representative of the epidemiological scenario under investigation.

Another limitation concerns the in situ treatment of animals with a clinical and epidemiological diagnosis of sporotrichosis, which may entail additional risks due to drug-related adverse effects, including gastrointestinal reactions and potential hepatotoxicity [5]. However, this was mitigated by the presence of dedicated caregivers with established bonds to the animals, ensuring appropriate medication administration and daily clinical monitoring. Furthermore, the existence of a structured and institutionalized population management program contributed to robust surveillance and appropriate clinical management, although such conditions may not be readily reproducible in other settings.

Conclusion

Resident animals, predominantly neutered and presenting less extensive lesions, showed a more favorable prognosis and shorter treatment duration, enabling in situ management; whereas abandoned animals, mostly unneutered males with extensive lesions, required longer treatment periods and involved greater logistical complexity and costs.

Capture, immediate initiation of treatment, sterilization after clinical cure and continuous monitoring are essential strategies in the management of sporotrichosis within a No-kill policy. To tackle sporotrichosis effectively, especially in free-living animals, it is not enough to treat individual cases. A collective, preventive and sustainable effort is needed, involving the entire local community, so that a single healthy and harmonious human-animal relationship can be guaranteed.

In situ treatment of free-roaming cats, although not the best option, maybe the only alternative when capture is unfeasible. To do this, it is essential to understand the population dynamics of the area and assess the risks posed to human and animal health by the permanence of positive animals.

The responsible caretaker must be committed to feeding and administering medication, as well as receiving information about the disease and prevention measures. Ideally, animals should be isolated to avoid environmental contamination and infection of other animals and humans. In areas with a history of sporotrichosis and positive colonies, active surveillance is essential to detect clinical signs and initiate treatment in affected individuals as early as possible. Therefore, the strategy must rely on constant monitoring and immediate therapy upon the manifestation of compatible clinical signs. Furthermore, there is a clear need to reinforce educational actions on responsible guardianship and combating abandonment, since animals that receive proper care have a shorter treatment time and consequently a better prognosis.

Supporting information

Acknowledgments

The authors specifically thank all the volunteers of the Dog and Cat Management Program at the Federal University of Minas Gerais (UFMG). The authors also thank the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES), National Council for Scientific and Technological Development (CNPq) and the Postgraduate Program in Animal Science of the School of Veterinary, at the Federal University of Minas Gerais State (UFMG).