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Caused by a fungus that naturally lives in the soil, sporotrichosis is a ringworm that causes serious damage in cats and can also affect humans.

Image: Isabella Dib Gremio

Sporotrichosis is a disease caused by a fungus that naturally lives in the soil, the Sporothrix sp.. In Brazil, the Sporothrix brasiliensis is the most prevalent etiological agent, although S. schenckii is also found to a lesser extent. Cats are the biggest victims of the problem, which is a ringworm causing serious and potentially fatal injuries if not treated in a timely manner. For a long time, sporotrichosis was known as the "gardener's disease", as it was common among these professionals, as well as in farmers and other individuals who had contact with plants, soil or moist boards contaminated by the fungus.

the fungus Sporothix spp it inhabits nature and is present in soil, straw, vegetables, thorns and wood. Humans can become contaminated through contact with these materials, but currently the most common form is through cats. Cats are more exposed to the disease, as it is common for them to enjoy playing with vegetables or even on the ground. When cats transmit the disease to humans, it is called zoonotic sporotrichosis.

Through claws (the technical term is “scratching”), infected cats transmit the fungus to other felines, dogs and people alike. Lesions in humans and dogs are generally not as severe as in cats and are rarely life-threatening. Even in cats, which are more affected, the disease is curable, but treatment is expensive and time-consuming. Sporotrichosis is concentrated in homeless animals or in needy communities, which makes treatment difficult due to the high cost. Because of this, many owners abandon infected cats, which causes the disease to spread even further.

"In Brazil, human sporotrichosis is not a compulsory notification disease and, therefore, its exact prevalence is unknown", said veterinarian Isabella Dib Gremião, from the Clinical Research Laboratory on Dermatozoonosis in Domestic Animals of the National Institute of Infectology Evandro Chagas from the Oswaldo Cruz Foundation (INI/Fiocruz).

"Since July 2013, due to the status hyperendemic of sporotrichosis in Rio de Janeiro, the disease has become mandatory notification in the state. At INI/Fiocruz alone, a reference unit in Rio de Janeiro, more than 5,000 human cases and 4,703 feline cases were diagnosed by 2015,” said the researcher.

Only that year, according to data from the Sanitary Surveillance of the city of Rio de Janeiro, there were 3,253 feline cases. In 2016, there was an increase of 400% in the number of animals diagnosed. In all, the agency provided 13,536 consultations in 2016 – whether in public veterinary institutes, in home or community care. In people, the Municipal Health Department of Rio de Janeiro recorded, in 2016, 580 cases.

These statistics refer only to reported cases. The researchers point out that the level of underreporting must be high. Gremião is the first author of a work that has just been published in the magazine PLOS Pathogens on the transmission of sporotrichosis between cats and humans.

Biologist Anderson Rodrigues, a professor at the Federal University of São Paulo (Unifesp), another of the authors of the article, studies the genomics of the many species of the genus Sporothrix (there are 51, five of which are of medical relevance) to compare their DNA with that of the S. brasiliensis, the causative agent of the emerging disease in Brazil and by far the most virulent species.

In a postdoctoral research, Rodrigues described in 2016 a new species, Sporothrix chilensis, isolated from the diagnosis of a human case in Viña del Mar, Chile. "The comparative analysis of the genomes of Sporothrix will allow the identification of groups of genes specifically linked to virulence factors and survival mechanisms during the infection”, said Rodrigues.

"Our expectation is to significantly broaden the understanding of genetic diversity and physiological response in Sporothrix, an initial step towards the development of better methods to control these pathogens”, he said.

Cases of sporotrichosis in the world from 1952 to 2016 (PLOS Pathogens)

Transmission and treatment

It is not known how the Sporothrix brasiliensis started to infect cats. Until the increase in the number of cases in Rio de Janeiro, sporotrichosis was considered a very sporadic and occupational disease, Rodrigues recalls.

It is known as the “gardeners' disease” because the first cases diagnosed in the United States in the late 19th century were among rose growers. The fungus occurs naturally in the soil and on the surface of plants such as rose bushes. In the US case, patients became infected by scratching their spines.

The first diagnosis of animal sporotrichosis in Brazil dates back to 1907, among naturally infected rats in the sewers of the city of São Paulo – the first feline cases occurred in the 1950s.

“The disease traditionally affected one to two people a year. But in 1998, the total number of cases in Rio de Janeiro began to grow”, said Professor Zoilo Pires de Camargo, head of the Medical and Molecular Mycology Laboratory at Unifesp and coordinator of the Thematic Project “Molecular Biology and Proteomics of fungi of medical interest: Paracoccidioides brasiliensis and Sporothrix schenckii” , conducted from 2010 to 2016 with the support of FAPESP, Rodrigues' advisor in his post-doctorate.

From Rio de Janeiro, the disease has spread to other cities in Rio de Janeiro, and from there to other states. The recent emergence of feline sporotrichosis in the metropolitan region of São Paulo draws the attention of researchers at Unifesp and the Center for Control of Zoonoses (CCZ), where 1,093 cases have been confirmed in recent years.

There are already cases of sporotrichosis throughout the Southeast and South of Brazil. They are also beginning to manifest themselves in the Northeast region and abroad. In Buenos Aires, in 2015, five cases of sporotrichosis in humans were reported.

Although there are other species of fungi in the genus Sporothrix spread around the world and that also cause the disease, according to researchers, the Brazilian epidemic is unique, because of the etiological agent attacking felines, for having become a zoonosis from the time that cats started transmitting the fungus to humans and for the expressive number of cases.

“In the annals of medicine, the biggest outbreak of sporotrichosis would have occurred in the 1940s among miners in South Africa. Sporothrix. Once the outbreaks were identified, the wood was treated and the epidemic ended,” said Camargo.

In Brazil, in addition to the lack of capacity to make large-scale diagnoses at the municipal, state and national levels, there is a lack of access to medicines to treat the disease.

The reference drug is the high-priced antifungal itraconazole. Every month and over six months, at least four boxes are needed: two to treat the animal and another two for the guardian, if he is sick. As every cat owner knows, no matter how dear their pussies are, they scratch, especially in situations of stress such as when giving medicine.

As long as it is not free of the fungus, the cat can continue to transmit the fungus. After the first or second month of treatment, the lesions usually disappear, but the fungus does not. “The interruption of treatment before six months can lead to the resurgence of the lesions”, said Camargo.

It is not known why cats are so susceptible to Sporothrix brasiliensis nor because the disease is so serious in them. An injured cat may have the fungus in its claws. When fighting another cat, a dog, or chasing a mouse, it passes the fungus through scratches.

Scratches in cats usually occur on the head, the most common site for lesions to appear, but not the only one. The fungus present in lesions progressively destroys the epidermis, dermis, collagen, muscles and even bones. In addition, the fungus can affect the internal organs, worsening the clinical picture.

“When the animal reaches these conditions, it is common for it to be abandoned by its owners. Go to the street and feed the transmission chain. If the cat dies, it is buried in the backyard or in a dump, which will be contaminated by the fungus present on the corpse”, said Gremião.

According to the researcher, in addition to the ability to diagnose all cases and access to medication, combating the outbreak of sporotrichosis requires governments to carry out educational campaigns on the responsible care of the animal. An infected cat cannot be abandoned, it needs to be treated and, if it doesn't resist, ideally it should be cremated, to interrupt the fungus transmission chain.

Articles

The article Zoonotic Epidemic of Sporotrichosis: Cat to Human Transmission (doi:10.1371/journal.ppat.1006077), by Isabella Dib Ferreira Gremião, Luisa Helena Monteiro Miranda, Erica Guerino Reis, Anderson Messias Rodrigues and Sandro Antonio Pereira.

The article Sporothrix species causing outbreaks in animals and humans driven by animal-animal transmission (doi:10.1371/journal.ppat.1005638), by Anderson Messias Rodrigues, G. Sybren de Hoog and Zoilo Pires de Camargo.

The article Sporothrix chilensis sp. Nov. (Ascomycota: Ophiostomatales), a soil-borne agent of human sporotrichosis with mild-pathogenic potential to mammals (doi: 10.1016/j.funbio.2015.05.006), by Anderson Messias Rodrigues, Rodrigo Cruz Choappa, Geisa Ferreira Fernandes, G. Sybren de Hoog and Zoilo Pires de Camargo.

The article Feline sporotrichosis due to Sporothrix brasiliensis: an emerging animal infection in São Paulo, Brazil (doi: 10.1186/s12917-014-0269-5), by Hildebrando Montenegro, Anderson Messias Rodrigues, Maria Adelaide Galvão Dias, Elisabete Aparecida da Silva, Fernanda Bernardi and Zoilo Pires de Camargo.