Closing the diagnostic gap to control zoonotic sporotrichosis in the Americas

Sporotrichosis is a highly prevalent implantation mycosis, with an estimated burden exceeding 40,000 cases annually.¹ Although robust epidemiological data remain scarce and are likely underestimated, this figure suggests that sporotrichosis may be the most common implantation mycosis, exceeding mycetoma, which is estimated at around 9000 cases globally, and chromoblastomycosis, at approximately 10,000 cases.¹ The disease shows a highly heterogeneous distribution, with a marked concentration in hyperendemic regions of Latin America, particularly Brazil, Mexico, Colombia, and Peru, where incidence rates can reach up to 25 per 1000 individuals in some settings. The vast majority of sporotrichosis cases are caused by members of the Sporothrix schenckii complex, including S. schenckii sensu stricto and Sporothrix brasiliensis. Among these, S. brasiliensis is notable for its zoonotic transmission to humans via cats and is geographically concentrated in Brazil. This species is responsible for a large and ongoing outbreak among cats in the country, which has now entered its third decade.²

Reported mortality in sporotrichosis varies depending on the population and disease severity. In a large clinical cohort, one year mortality reached about 17%, with higher risk among older patients, those with neoplasms, and individuals presenting with lymphocutaneous or disseminated forms, as well as markers of systemic inflammation such as hyperferritinemia.³ Although HIV-associated cases represented a small proportion, they were more frequently linked to pulmonary and disseminated disease.³ Treatment of human sporotrichosis is prolonged and often ineffective. An analysis of severe, disseminated sporotrichosis caused by S. brasiliensis reported a median treatment duration of 784 days, ranging from 7 to 3115 days. Cure was achieved in 45.9% of patients, whereas 24.3% died as a direct result of sporotrichosis.⁴

The rapid expansion of zoonotic sporotrichosis across South America represents a growing public health challenge that demands attention from health authorities.² Driven largely by transmission from infected cats, particularly in urban environments with large populations of free roaming animals, the disease has evolved into a complex One Health problem. In Brazil and neighboring countries, sustained transmission cycles now affect both animal and human populations,^5,6 increasing pressure on municipal services, veterinary systems, and public health infrastructure.

At the center of this issue is the lack of rapid, affordable, and field deployable diagnostics for use in animal populations, especially among unowned cats. While animals with owners can access veterinary care, a large proportion of transmission is sustained by those outside this system. For municipal health workers and zoonosis control teams, the inability to quickly determine whether an animal is infected directly limits intervention. Decisions such as isolation, treatment, or release are often made under uncertainty, leading either to inefficient use of resources or continued dissemination of the pathogen.

An important barrier lies in the structural reality of the settings most affected by sporotrichosis. Transmission is strongly linked to urban peripheries and underserved areas where laboratory capacity is limited, supply chains are unstable, and cold storage cannot be reliably maintained.² Frontline teams operate in decentralized environments with high caseloads and limited personnel, leaving little room for complex workflows. Diagnostics that depend on specialized equipment or advanced training are therefore unlikely to be implemented at scale, regardless of performance.

Current diagnostic methods are poorly aligned with these realities. Culture is slow and infrastructure dependent, while cytology requires technical expertise that is not consistently available in peripheric settings. As a result, timely decision making in the field remains constrained. Alternative strategies have been explored,^7,8 but none have translated so far into broadly useable tools for public health programs. Traditional serological assays often rely on blood sampling, which is impractical for large scale use in animals without owners.^7,9 In Brazil, a commercial serological ELISA assay for feline sporotrichosis is available, offering rapid detection of IgG antibodies (Cat Sporothrix IgG ELISA Kit; BIDiagnostics).⁷ However, despite its advantages, this test still requires laboratory infrastructure, refrigeration of reagents, and is restricted to facilities with greater resources. Molecular methods offer high sensitivity but are costly and dependent on equipment and supply systems incompatible with field deployment.¹⁰ Despite advances in laboratory science, there remains no diagnostic approach that effectively supports surveillance and control at scale.

For public health authorities, this gap has direct consequences. Without timely identification of infected animals, interventions become reactive rather than preventive. Opportunities to interrupt transmission early are lost, contributing to sustained endemicity, increasing costs for health systems, and a higher risk of human infection, particularly in densely populated urban settings.

Addressing this bottleneck requires a shift in how diagnostic tools are defined and prioritized. The key question is not only analytical performance, but whether a tool can function under real world conditions. The ideal diagnostic should deliver results within a single encounter, be simple enough for minimally trained personnel, and be affordable for large scale use. It must also function without refrigeration or complex logistics and rely on noninvasive sampling approaches suitable for field conditions. Within a One Health framework, the benefits of such a tool would be substantial. Rapid identification of infected animals would enable targeted isolation and treatment, reducing environmental reservoirs and lowering the risk of transmission to humans. At the same time, it would support more efficient allocation of resources, strengthen surveillance, and improve integration between veterinary and public health systems.

The urgency of investing in this area is reinforced by the expanding geographic footprint of sporotrichosis. Urbanization, environmental disruption, and animal mobility increase the risk of introduction into new regions.¹¹ Without adequate surveillance tools, outbreaks may remain undetected until they become difficult to control. Therefore, investment in an accurate, rapid, and cost-effective diagnostic test for animals is essential not only to enhance current responses but also to prevent the further spread of the disease.

We urge public health authorities, funding agencies, and decision makers to support the development and implementation of rapid, cost effective, and infrastructure independent diagnostic tools for animal sporotrichosis. Strengthening diagnostic capacity is a pragmatic step toward more efficient control strategies and a necessary condition to reduce the burden of this expanding zoonosis on both animal and human health.

Contributors

MLR conceived the commentary and led manuscript development. CMS edited the first version. MLR provided critical input and revisions. Both authors approved the final version.

Ethics

Ethics: No human participants or identifiable data.

Consent for publication

Not applicable.

Use if artificial intelligence

Copilot (https://www.copilot.com) was employed for grammar revision, and the manuscript underwent a thorough review for accuracy. Subsequently, both authors approved the revised manuscript. C.M.S. and M. L. R. bear full responsibility for the content of this manuscript.

Declaration of interests

M.L.R. reports support for the present manuscript from CAPES (Brazil), the UK Department of Health and Social Care (Failsafe Program, UK), the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (USA), CNPq (Brazil), and Fiocruz Program for Research Stimulation, with payments made to his institution for research that he coordinates. M.L.R. also reports employment support from Fiocruz and UFRJ in the form of salary. C.M.S. reports receiving a fellowship from VPPCB, Oswaldo Cruz Foundation Fiocruz, and support for attending meetings in the form of the MMSA Angela Restrepo Latin American travel award sponsored by IMMY. The funders had no role in writing or submission. M.L.R. and C.M.S. declare no other competing interests.