Epidemiology of Clinical Sporotrichosis in the Americas in the Last Ten Years

Background: Sporotrichosis is a fungal infection caused by species of the Sporothrix genus. Presently, the prevalence of sporotrichosis in the Americas is unknown, so this study aims to analyze the cases reported in the past 10 years. Methods: An advanced search was conducted from 2012 to 2022 in English and Spanish in PUBMED, SciELO, and Cochrane, with the terms: “sporotrichosis”, “lymphocutaneous sporotrichosis”, “fixed sporotrichosis”, “mycosis”, “Sporothrix spp.”, “Sporothrix complex”, “S. schenckii sensu stricto”, “S. schenckii sensu lato”, “S. globose”, “S. brasiliensis”, “S. luriei”. Sporotrichosis is a fungal infection caused by species of the Sporothrix genus associated with “pathogenicity” or “epidemiology”. Results: A total of 124 articles were found in the Americas, corresponding to 12,568 patients. Of these, 87.38% of cases were reported in South America, 11.62% in North America, and 1.00% in Central America and the Caribbean. Brazil, Peru, and Mexico had the highest number of cases. The most prevalent etiological agents were S. schenckii complex/Sporothrix spp. (52.91%), S. schenckii (42.38%), others (4.68%), and Not Determined (ND) (0.03%). The most frequent form of the disease was lymphocutaneous infection; however, the infection type was not determined in 5639 cases. Among the diagnostic methods, culture was the most used. Conclusions: There is a high occurrence of cases reported in the literature. South America is the region with the highest number of reports because of its environment (climate, inhalation of spores, etc.), zoonotic transmission (scratches and sneezes from contaminated animals), and possible traumatic inoculation due to outdoor activities (agriculture, gardening, and related occupations). Molecular diagnosis has not been sufficiently developed due to its high cost.

For this subcutaneous infection to develop, a direct trauma must occur first. For example, inoculation occurs when the skin is punctured by plants with thorns, gardeners are a classic case of this. Also, inoculation can occur through fomites that contact contaminated soil. For instance, people who wear sandals can suffer trauma from stones, firewood, or thorns with fungal spores on their surface [2,3]. With all the above, it can be inferred that this type of fungal infection is associated with regions where the main livelihood is agriculture, that is, in environments where the climate is tropical and subtropical. Another form of transmission, which has been increasing in recent times in some regions of the continent such as Brazil, Argentina, Paraguay, and Panama, has been reported to result from scratches, bites, pecks, and stings from different animals [1][2][3][4].
For this subcutaneous infection to develop, a direct trauma must occur first. For example, inoculation occurs when the skin is punctured by plants with thorns, gardeners are a classic case of this. Also, inoculation can occur through fomites that contact contaminated soil. For instance, people who wear sandals can suffer trauma from stones, firewood, or thorns with fungal spores on their surface [2,3]. With all the above, it can be inferred that this type of fungal infection is associated with regions where the main livelihood is agriculture, that is, in environments where the climate is tropical and subtropical. Another form of transmission, which has been increasing in recent times in some regions of the continent such as Brazil, Argentina, Paraguay, and Panama, has been reported to result from scratches, bites, pecks, and stings from different animals [1][2][3][4].
There are several techniques for detecting sporotrichosis, including Sabouraud dextrose agar cultures, lactophenol blue or erythromycin staining, histopathological studies, and PCR sequencing, among others [5][6][7] (Figure 1).  As for the clinical forms of sporotrichosis, various types have been described, such as the lymphocutaneous, fixed cutaneous, and, as mentioned earlier, the disseminated or hematogenous forms where both organs and tissues can be affected . The latter is the rarest because the recommended antifungal regimens are usually effective; however, in patients with alterations in cellular immunity, these infections can spread [2][3][4].

Materials and Methods
An advanced search was conducted in English and Spanish languages in the engines Medical Literature Analysis and Retrieval System Online (MEDLINE/PUBMED), Scientific Electronic Library Online (SciELO), and Cochrane Database. Because the systematic review was performed for the 10 last years (2012-2022), both taxonomical classifications were used. The applied terms were "sporotrichosis", "lymphocutaneous sporotrichosis", "fixed sporotrichosis", "Sporothrix spp." and "Sporothrix schenckii complex", "S. schenckii sensu stricto", and "S. schenckii sensu lato", Sporothrix schenckii, (Sporothrix schenckii), Sporothrix brasiliensis (S. brasiliensis), Sporothrix globosa (S. globosa), Sporothrix luriei (S. lurieri), Sporothrix pallida (S. pallida), Sporothrix mexicana (S. mexicana), and Sporothrix chilensis (S. chilensis) associated with "pathogenicity" or "epidemiology". The total number of articles found was 243. The review was performed based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) (Figure 2). After reading the titles and reviewing the complete text, the most relevant papers to develop this article were identified. At the end of the selection process, 127 articles were chosen. The review was performed based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA).

Epidemiology of Sporotrichosis in North America
A total of 48 publications related to sporotrichosis were found in North America . There were 1460 patients in total associated with infection caused by species of the
The most frequent variety reported was lymphocutaneous with 956 cases, followed by fixed cutaneous with 388 cases, and the disseminated form with 83 . A lymphocutaneous presentation evolved into a disseminated after 10 months. The least frequent varieties were the disseminated cutaneous with 16 cases, disseminated cutaneous with affected mucous membranes and arthritis with 3 cases each, and the pulmonary form with 2 cases. Finally, lymphadenitis, meningitis, laryngotracheal joint, visceral fungemia, visceral infection associated with fungemia, an atypical presentation, and a visceral presentation with fungemia and mucosal involvement were only reported in one case each. The most common reported etiological agent with the new taxonomical classification was Sporothrix spp. with 85.00% (1241/1460), followed by S. schenckii with 14.38% (210/1460), S. globosa with 0.54% (8/1460), and S. mexicana with 0.068% (1/1460) .
In terms of the diagnosis, fungal culture was the most frequently used diagnostic methodology with 33/48, followed by histopathological examination with 20/48. It is worth noting that the histopathological examination was always accompanied by fungal cultures. PCR sequencing was the third method used in 11/48 studies. For this diagnostic tool, the Calmodulin gene was used in 7 cases, the ITS1-2 region in 3 cases, and an unspecified gene in 1 case. Also, the MALDI-TOF and the agglutination latex test were used for diagnosis in two reports. Finally, the use of the Sporotrichin Skin Test and physical examination was mentioned in one report, and one case was reported without describing the employed diagnostic method .
Regarding diagnosis, fungal culture was used as a diagnostic method in all articles (8/8), followed by histopathological examination (5/8). In this case, also, the histopathological examination was always accompanied by fungal cultures. PCR sequencing (2/8) employing the calmodulin gene in one article and the ITS1-2 region in the other was also used as a diagnostic tool. Lastly, diagnosis with microscopy using lactophenol blue was mentioned in two reports (  ND: Not Determined.

Discussion
A total of 124 publications were found with reports related to sporotrichosis in the Americas in the last 10 years, with 12,636 patients associated with infection caused by species of the genus Sporothrix. Interestingly, it was observed that 87.45% (11,050) of these cases were reported in South America, 11.55% (1460) in North America, and 1.00% (126) in Central America and the Caribbean . The countries that presented the highest number of cases during the analyzed period were Brazil (5546-43.89%), Peru (4792-37.92%), and Mexico (1431-11.32%). It should be noted that in the case of Brazil and Peru, there were various reports with several cases from a time period ranging from 25 to 50 years [66,67,75,86]. As previously mentioned, sporotrichosis is a disease caused by a thermodymorphic fungus of the genus Sporothrix. It is known that this subcutaneous disease, although cosmopolitan, generally occurs in both tropical and subtropical regions. The latter could explain, in some part, the high prevalence in Latin America, being endemic in this region [1][2][3][4]129]. However, three countries (Brazil, Peru, and Mexico) have specific characteristics that increase the number of cases. In Brazil and adjacent countries (for example, Argentina and Paraguay), an increasing number of cases have been associated with zoonotic infection, mainly from infected cats through scratches or sneezes [3,4]. Since the zoonotic transmission of S. brasiliensis is the most important form of communication, it is recommended that hygienic measures be taken regarding domestic animals such as cats, rodents, etc., due to possible infections. If it is diagnosed in animals, it must be treated immediately, and gloves must be used when handling animals with injuries [2][3][4].
In Mexico, sporotrichosis is considered endemic and an occupational disease due to the different sources of infection. The climate of some regions in Mexico is perfect for the characteristics of this type of mycosis to increase its incidence. Although tropical and subtropical climates are preferred by this fungus, in this country, the cold and dry seasons are the contagion peaks of these pathological agents. The states that are more affected are Mexico City, Puebla, Jalisco, Michoacan, the State of Mexico, and Guanajuato. In these states, agriculture is one of the most important economic activities, which explains the high incidence of the Sporothrix contagion [130]. Thus, the principal recommendation in this region is the use of gloves or long-sleeved clothing when carrying out work activities where these species are endemic.
Regarding the etiological agents responsible for the types of sporotrichosis, it is important to specify that they were referred to both in the table and in the text in the way they were named in the articles that were analyzed. Since most of them were written and published before the changes in taxonomical classification, they do not consider the clinical and environmental clades classification instead of the Sporothrix schenckii complex.
Likewise, within the systematic review, Ophiostoma stenoceras appears, which in the taxonomic classification of Sporothrix is represented in its sexual state, in the year the report was made. Nevertheless, in 2016, Beer et al. concluded through phylogenetic analyzes that the genus Sporothrix was different from the genus Ophiostoma, but that was before considering its sexual state. Officially, the sexual status of Sporothrix is not known, and in this case, Ophiostoma stenoceras was included according to the regulations that governed the taxonomy before the divorce between the two genders occurred [132].
On the other hand, the most frequent type of sporotrichosis was the lymphocutaneous with 4288 cases, followed by the fixed cutaneous with 2340 cases, the disseminated or systemic with 103, the disseminated cutaneous with 52 cases, other with 215 cases, and 5760 cases were ND. By being a subcutaneous mycosis, the lymphocutaneous form is the most frequent one because sporotrichosis mainly affects the lymph nodes of the skin and the subcutaneous tissue, producing ulcers and thereby affecting the lymphocutaneous system [133]. The infection begins in the form of an inoculation chancre. Subsequently, erythematous nodular lesions arise, which follow the trajectory of the lymphatic vessels, mainly affecting the face and upper and lower limbs. Another common form is the fixed cutaneous, which occupies the second place in the Americas to the present date. This type is of a fixed form at the inoculation site of the fungus, affecting mainly children, and it is observed as a verrucous plaque. Its presence demonstrates a high immunity response from the patient. Being a disease of this body region, it has a low prevalence in other organs or tissues. However, the disseminated or hematogenous form may be cutaneous or systemic [5][6][7][8]. Systemic sporotrichosis can cause respiratory and lung disorders, osteomyelitis, arthritis, and meningitis. It is important to note that the type of condition affecting the patients (5760 cases) was not mentioned in several of the reported cases analyzed in this publication.
Concerning diagnosis, various methods, both phenotypic and genotypic, have been used to detect the infection caused by this etiological agent [129]. Within the phenotypic methods, we can name (1) mycological cultures. This technique seeks the growth of the colony in a radial form (approximately 3 to 4 days) with a creamy consistency, and subsequently, the development of mycelium is observed for its identification (Gold Standard). Finally, it is suggested to perform a lactophenol blue staining to observe the microconidia in a sympodial arrangement along the mycelium. (2) serological diagnosis using sporotricine and immunodiffusion tests, immunoelectrophoresis, latex agglutination, etc. (3) histopathological diagnosis, an excisional biopsy of the nodular lesion is performed that may show granulomatous and necrotizing dermatitis, which can be stained with Hematoxylin and Eosin (HE) Schiff's Periodic Acid (PAS), or Grocott-Gomori Methenamine Silver (MSG) to confirm the presence of asteroid bodies [5][6][7][8].
Nonetheless, genotypic identification tests are preferred since phenotypic techniques have disadvantages, such as being laborious, presenting variable results from the clinical field, and requiring many samples to reach a diagnosis. Therefore, different PCR techniques have been used for genotypic identification tests utilizing diverse genetic or molecular markers that have been developed [5].
In this systematic review, the culture turned out to be the most used diagnostic method throughout the continent, being performed in 107 of the 127 articles reviewed. Histopathological examination was the second most used diagnostic technique, found in 43 publications. In addition, PCR sequencing was used 38 times, direct microscopy 21 times, and microscopy with lactophenol blue was reported in 9 articles. Lastly, other techniques were used to detect sporotrichosis; however, these were not utilized routinely.