Veterinary Clinic Cluster Ties Canine Sporotrichosis to Sporothrix brasiliensis in Argentina
A 4-year-old toy poodle in Puerto Iguazú became the canine anchor case in a veterinary cluster that linked one dog and three cats to Sporothrix brasiliensis in 2024. The dog had been attacked by two free-roaming dogs, then underwent debridement and surgical closure of deep lacerations at a veterinary clinic before leaving hospital on amoxicillin/clavulanic acid and prednisolone. Within about a month, both surgical sites broke down, purulent drainage appeared, and ulcerative skin lesions spread across the body, with respiratory signs adding to the clinical picture.
The trajectory fit a fungal process far better than a routine postoperative bacterial wound infection. Cytology from lesion and nasal swabs showed yeast structures consistent with Sporothrix species, culture confirmed the genus, and sequencing of the internal transcribed spacer region and calmodulin gene identified S. brasiliensis. Oral itraconazole for 122 days produced complete clinical resolution. In a region where feline sporotrichosis had already been circulating, the dog’s illness was not an isolated curiosity; it became the index signal in a broader veterinary exposure cluster.
A Postoperative Wound Became the Entry Point for a Zoonotic Outbreak
The surrounding cases sharpen the concern. At the same clinic, a 6-month-old cat had been hospitalized since mid-August with a persistent, antimicrobial drug–refractory suppurative surgical-site lesion after ovariohysterectomy in late July, and respiratory signs were also present. Another 5-month-old cat developed a similar refractory surgical wound after ovariohysterectomy in early September. An 11-month-old cat with outdoor access underwent the same surgery in June and later developed a suppurative incision infection, then additional cutaneous lesions and respiratory disease.
In each feline case, sporotrichosis was not suspected at first. That delay matters clinically because fungal postoperative infections rarely receive the same immediate attention as bacterial surgical-site infections in veterinary practice. Direct examination and culture from nasal and lesion swabs ultimately supported Sporothrix infection in all three cats, while sequencing confirmed S. brasiliensis in two of them. Two of the cats deteriorated despite itraconazole and were euthanized; one was lost to follow-up after treatment began. The contrast between delayed recognition and rapid progression is stark. These were not trivial wound complications but invasive infections with mucocutaneous and respiratory involvement.
Environmental Sampling Raised Concern for Indirect Transmission
The epidemiologic investigation began after cytology from the dog and one cat showed yeast forms on October 24, 2024. Veterinary records were reviewed, owners were interviewed, household animal contacts were assessed, and environmental samples were taken from the clinic. The dog had no household animal contacts. One cat lived with a clinically healthy, culture-negative cat. Another cat lived with a dog that later developed surgical-site and dorsal lesions, although sampling that dog was not authorized. The fourth cat had no reported animal contacts.
The timing of clinic stays was especially telling. One cat had been hospitalized before the dog, with overlapping stays and adjacent kennels. The two surgical feline cases had undergone ovariohysterectomy at the same clinic before developing lesions. No person reported skin lesions after contact with affected animals, but prevention counseling and safe-handling guidance were provided to veterinary personnel, owners, and household members.
Environmental swabs added another layer of concern. One surgical table and two instruments from an adjacent countertop yielded filamentous fungal growth phenotypically compatible with Sporothrix species. Molecular identification of the environmental isolates did not succeed, so species-level confirmation was not possible. Even so, the recovery of Sporothrix-like organisms from clinic surfaces and instruments supports the plausibility of indirect spread through contaminated fomites or surfaces.
Molecular Findings Support a Shared Sporothrix brasiliensis Clade
Phylogenetic analysis placed all clinical isolates within the S. brasiliensis clade. The ITS-rDNA sequences were identical among the clinical isolates and the reference strain CBS120339T. Across the concatenated sequences, the dog isolate showed 99.89% identity with the other clinical isolates, differing from the reference strain by one nucleotide. Those data fit circulation of the same species in this setting, but they do not reconstruct the transmission chain.
Resolution remained limited. ITS-rDNA and calmodulin sequences were not granular enough to determine whether the dog and cats shared a single source or whether multiple clinic-linked exposures occurred. Microsatellite analysis or whole-genome sequencing would be needed to define directionality and map transmission with greater confidence. The study also did not systematically evaluate infection-control practices with a standardized protocol, leaving hand hygiene, personal protective equipment use, cleaning, disinfection, and environmental controls outside the reach of the investigation.
The evidence still points in one direction. A cluster of epidemiologically linked canine and feline sporotrichosis cases, all tied to a single veterinary clinic, is consistent with healthcare-associated exposure to S. brasiliensis.
Why the Diagnosis Matters in Endemic Regions
In veterinary settings, bacterial pathogens remain the most common explanation for surgical-site infection. Fungal infections are often not pursued early, and this cluster shows how easily they can be missed when postoperative lesions fail standard antimicrobial therapy. In regions with active S. brasiliensis transmission, sporotrichosis belongs in the differential diagnosis of nonhealing postoperative wounds, especially when lesions are suppurative, refractory to antibiotics, or accompanied by respiratory disease.
Biology supports that concern. S. brasiliensis is well adapted to zoonotic spread, primarily through infected cats, and it can persist in organic material and contaminated environments. That makes a clinic more than a passive backdrop; it can become a setting where surgery, wound care, shared surfaces, and animal traffic intersect. In a place like Puerto Iguazú, where sporotrichosis outbreaks in cats have already been documented and leishmaniasis is also endemic, compatible skin lesions deserve a broad infectious differential rather than a narrow presumption of bacterial infection alone.
For the dog, the possible route remains unresolved. Direct inoculation through the bite wounds from the attacking dogs remains possible, and the attacking animals were not evaluated. Still, dog-to-dog transmission of S. brasiliensis is rarely documented, and the co-occurrence of feline clinic cases makes indirect healthcare-associated exposure difficult to dismiss.
The practical lesson from this cluster is not abstract. Early mycologic diagnosis, molecular surveillance, and rigorous infection-control practices are essential in veterinary settings where S. brasiliensis circulates. Without them, a postoperative wound can become the first visible sign of a broader transmission problem.