Research and analysis

HAIRS risk statement: sporotrichosis

Published 17 January 2024

About the Human Animal Infections and Risk Surveillance group

This document was prepared by the UK Health Security Agency (UKHSA) on behalf of the joint Human Animal Infections and Risk Surveillance (HAIRS) group.

HAIRS is a multi-agency cross-government horizon scanning and risk assessment group, which acts as a forum to identify and discuss infections with potential for interspecies transfer (particularly zoonotic infections).

Members include representatives from:

• UKHSA

• the Department for the Environment, Food and Rural Affairs

• the Department of Health and Social Care

• the Animal and Plant Health Agency (APHA)

• the Food Standards Agency

• Public Health Wales

• Welsh Government

• Public Health Scotland

• Scottish Government

• Public Health Agency of Northern Ireland

• the Department of Agriculture, Environment and Rural Affairs for Northern Ireland

• the Department of Agriculture, Food and the Marine, Republic of Ireland

• Health Service Executive, Republic of Ireland

• Infrastructure, Housing and Environment, Government of Jersey

• Isle of Man Government

• States Veterinary Officer, Bailiwick of Guernsey

Information on the risk assessment processes used by the HAIRS group can be found on GOV.UK.

Version control

Date of this assessment: December 2023

Version: 1.0

Completed by: HAIRS members and external experts

Non-HAIRS members consulted:

• James Barnacle, Specialist Registrar in Infectious Diseases, Imperial College Healthcare NHS Trust

• Valentin Dominguez, Veterinary Advisor (One Health), Animal and Plant Health Agency

• Lisa Glaser, Senior Scientist, UKHSA’s Zoonoses Team

• Eva Emanuel, Senior Scientist, UKHSA’s Zoonoses Team

• UKHSA’s Public Health and Clinical Response Evidence Team

• UKHSA’s National Mycology Reference Laboratory

Summary

Sporotrichosis (also known as ‘rose gardener’s disease’) is an infection caused by a group of dimorphic fungi from the genus Sporothrix, which have a global distribution. Humans typically become infected through contact with fungal spores in contaminated environments. Zoonotic transmission of sporotrichosis has also been described, and primarily occurs from bites, scratches or direct contact with secretions from cutaneous or mucosal lesions of infected animals, notably cats.

Human sporotrichosis infections in the UK are rare, with sporadic cases typically reported following environmental exposure. In 2022, a zoonotic outbreak involving 3 human cases of sporotrichosis caused by Sporothrix brasiliensis was reported in the UK, where the most likely source of infection was a domestic cat imported from Brazil. These were the first ever cases of cat-transmitted sporotrichosis identified in the UK, and the first cases of cat-transmitted sporotrichosis caused by S. brasiliensis reported outside of South America.

This risk statement provides a qualitative description of the current risk to the UK human population and highlights evidence gaps and recommendations for mitigating against the risk of zoonotic transmission.

Background

Sporotrichosis (also known as ‘rose gardener’s disease’) is an infection caused by a group of dimorphic fungi from the genus Sporothrix. The fungus is found globally in soil and on plant and organic matter. Sporotrichosis classically presents as cutaneous or lymphocutaneous ulcerated lesions following the traumatic inoculation of contaminated soil, plants, or organic matter (1).

Zoonotic transmission of sporotrichosis has also been described, and primarily occurs from bites, scratches or direct contact with secretions from cutaneous or mucosal lesions of infected animals, notably cats and, to a lesser extent, dogs. Transmission from mice, squirrels and armadillos has also been described (2). Sporothrix species have further been isolated from a range of other animal hosts, including horses, weevils, tiger-quolls, ants, beetles, termites and mites (3). The most commonly isolated Sporothrix species in animals is S. brasiliensis, followed by S. schenckii. Other species have also been isolated, including S. globosa and S. humicola.

The clinical presentation of sporotrichosis in humans can vary according to the host’s immunological status, the load and depth of the inoculum and the pathogenicity of the strain (4). According to the location of the lesions, sporotrichosis can be classified into cutaneous, mucosal, or extracutaneous forms.

In the cutaneous form, after penetrating through the skin, the fungus may extend along the adjacent lymphatic vessels (known as the lymphocutaneous form) or remain localised in the subcutaneous tissue. The lymphocutaneous form is reported to be the most frequent clinical presentation, followed by the localised cutaneous form (mainly affecting the upper limbs). Erythema nodosum (characterised by tender, red, raised skin areas usually found on the shins) and erythema multiforme (red, raised skin areas that can appear all over the body) have been reported in cases of sporotrichosis by zoonotic transmission.

Rarer clinical presentations of sporotrichosis include disseminated or immunoreactive forms. The hands and forearms are the most common site of infection (1, 5, 6), which corresponds to the extremities most exposed to trauma (for example, bites and scratches from infected animals). Compared with other Sporothrix species, the clinical presentation of S. brasiliensis is more often associated with both atypical disease and severe symptoms in humans, such as hypersensitive reactions, nervous system tropism and ocular infections (5).

In animals, the clinical presentation has mostly been investigated in felines. As opposed to humans, the cutaneous form presenting as multiple lesions appears to be the most common clinical presentation, predominantly on the nose and paws, followed by the mucosal form of the respiratory and upper digestive tract, and the lymphocutaneous form, respectively. Disseminated disease has also been reported in some feline cases. Sporotrichosis in cats has been reported to be most common in intact free-roaming males (1, 5); whom are more likely to engage in disputes resulting in an increased risk of injury caused by an infectious conspecific. Domestic cats are susceptible hosts of Sporothrix (7), from which S. brasiliensis is the most commonly isolated species, followed by S. schenckii, making these the 2 species most commonly associated with zoonotic transmission (5).

Since sporotrichosis is not a notifiable disease in animals nor humans in most countries, there is little information on its global incidence, and most of the information is obtained from case publications. Although human cases of sporotrichosis have been reported on all continents, a higher prevalence is found in tropical and temperate zones (1). The majority of human sporotrichosis cases are reported in South America; a study found that 87.45% (n=11,050) of cases in the Americas reported in the literature between 2012 and 2022 were identified in South America, 11.55% (n=1,460) in North America, and 1.00% (n=126) in Central America and the Caribbean. The most commonly isolated species from human cases in South America was S. brasiliensis, whereas in North and Central America and the Caribbean S. schenckii was more predominant.

The countries that reported the highest number of human cases were Brazil, Peru and Mexico (6). In Brazil and adjacent countries, such as Argentina and Paraguay, an increasing number of human cases have been associated with zoonotic infection, mainly from cats (8). Since S. brasiliensis is considered the most important species for zoonotic transmission, its higher prevalence in South America may be reflective of this change in epidemiology. S. brasiliensis possesses a greater invasive capacity, having become the predominant species in Brazil shortly after its first introduction into the country in the 1950s (8).

On the Asian continent, human cases of sporotrichosis have been mainly reported from Japan, China, India and Malaysia, where S. globosa is the most commonly identified species. Both S. schenckii and S. globosa have been increasingly associated with urban areas, and so the higher prevalence of these 2 species in North America and Asia, respectively, may be reflective of increased urbanisation in recent years (8).

Although human sporotrichosis was common in Europe in the early 1900s, notably in France, only sporadic cases are now reported (8). In recent years, only a small number of clinical isolates and case reports have been reported in the literature from Spain, Italy, France and the UK; all identified as either S. schenckii or S. globosa, and likely environmentally acquired (9 to 13). In 2022, however, an outbreak of 3 human cases of sporotrichosis caused by S. brasiliensis was reported in the UK, where the most likely source of infection was a domestic cat imported from Brazil. These were the first ever cases of cat-transmitted sporotrichosis identified in the UK, and the first cases of cat-transmitted sporotrichosis caused by S. brasiliensis reported outside of South America (14).

In the UK, there is no statutory duty for medical practitioners to report suspected sporotrichosis cases to the competent authority (for example, their local council or Health Protection Team). However, diagnostic laboratories must report all positive Sporothrix species samples to the UKHSA, as per Health Protection (Notification) Regulations 2010 (15). Similarly, there is no requirement for veterinary diagnostic laboratories to report identifications in animals to the APHA as sporotrichosis is not a statutory disease.

Possibility of human exposure

Sporotrichosis is a recognised infection in humans. Sporothrix species have been isolated globally from the environment and from a wide range of animal hosts (3). Although human isolations have been reported on all continents, clinical cases appear to be more common in tropical and temperate zones where high humidity and temperature promote fungal growth (1). Most human cases result from exposure to fungal spores in the environment when they are inoculated through a penetrating lesion on the skin. Certain occupational and outdoor leisure activities, such as gardening, horticulture, farming, fishing, hunting and mining, may result in greater exposure risk to fungal spores present in the environment (1).

Zoonotic transmission of sporotrichosis has also been described and primarily occurs from bites, scratches or direct contact with secretions from cutaneous or mucosal lesions of an infected animal. Cats appear to be particularly susceptible to infection as their lesions often contain high fungal loads (16). Transmission from dogs has also been reported, and to a lesser extent from mice, squirrels and armadillos. Due to the potential for zoonotic transmission, veterinarians, pet shop workers and other occupations working closely with companion animals, particularly with cats, may be at increased risk of exposure.

Sporotrichosis is extremely rare in the UK. A small number of clinical isolates from humans have been described in the literature in recent years, where the most likely source was environmental. Only one incident of zoonotic transmission has been reported (in 2022), when 3 individuals were infected with S. brasiliensis with the likely source of infection being a domestic cat imported from Brazil (14). The human cases included 2 household contacts of the cat, and a veterinarian who had treated the cat a month before their symptom onset. The first feline case of sporotrichosis in the UK, however, was reported in 2020, which was caused by S. humicola (17). No other cases in animals have been reported in the UK.

An epidemic of sporotrichosis among cats has been recognised in recent years in Brazil. A review of the number of domestic cat imports into the UK from Brazil found that the number of imported cats increased by 46% in 2019 compared to 2018, with 134 cats entering the country (Table 1). This number decreased in 2020 and 2021, which may be due to travel disruptions during the COVID-19 pandemic. By 2022, cat imports from Brazil had increased by 13% compared to the previous year. These numbers do not necessarily indicate the number of imported cats residing in the UK, and some imports may only be temporary or transitory.

Table 1. The number of UK imports of domestic cats from Brazil by year, 2017 to the end of July 2023

Year	Number of consignments	Number of cats	% change in cat import numbers from previous year
2017	46	89	-
2018	49	92	+3%
2019	65	134	+46%
2020	39	71	-47%
2021	35	63	-11%
2022	39	71	+13%
2023	40	46	-

The low number of cat imports into the UK from Brazil may not present a high exposure risk to the UK feline and human population, however, the great invasive capacity of S. brasiliensis after a potential single introduction point has been recognised (8). There is no legal requirement to test for sporotrichosis in cats intended to be imported into the UK, and no statutory scope for controls to be applied should sporotrichosis be present in an imported animal (unless there is non-compliance with the importation legal requirements (18)).

As a general clause, common to all animals intended to be exported, animals are to be in good health condition and fit to travel. Cats presenting with extensive skin lesions caused by sporotrichosis would therefore be unlikely to meet these criteria and be signed off for exportation by veterinarians. Cats imported into the UK would also be inspected at a Border Control Point by an official veterinarian, however, the incubation period of sporotrichosis in animals typically ranges from one to 10 weeks (14, 16), and so fungal disease progression during the journey for cats which are asymptomatic or have minor skin lesions at the pre-import stage would be expected to be slow and may pass inspection at Border Control. Barnacle and others reported likely S. brasiliensis transmission from an indoor domestic cat, which had lived in South-Eastern Brazil 3 years previously, suggesting that S. brasiliensis can lay dormant for many years. Thus, veterinarians should be vigilant in taking a travel history when seeing cats with unexplained lesions.

Impact on human health

Human cases of sporotrichosis have been reported worldwide, with the highest number of cases reported in South America (6). Cases have been reported in individuals aged between 2 days to 92 years, although the highest incidence globally is seen among those aged between 30 and 50 years (6). In Brazil, however, a study reported that children, the elderly and women with low socioeconomic status were the most affected groups with sporotrichosis (5). Although the overall proportion of male and female cases appears comparable in South America (5, 19) and globally (6), a higher proportion of male cases have been reported from North and Central America, and the Caribbean (6).

In humans, sporotrichosis has an average incubation period of 3 weeks, ranging from several days to 3 months after exposure (20). The most common clinical presentation of sporotrichosis in humans is the lymphocutaneous form. This typically begins as one or more erythematous papules at the inoculation site and develop into subcutaneous nodules which spread along the lymphatics and may ulcerate (16). General health is usually unaffected in the cutaneous and lymphocutaneous forms, although untreated lesions may persist for months or even years. Rarer clinical presentations of sporotrichosis include disseminated, pulmonary or immunoreactive forms, which may be life-threatening. The hands and arms are the most common site of infection (1, 5, 6); corresponding to the extremities most exposed to trauma. Compared with other Sporothrix species, the clinical presentation of S. brasiliensis is more often associated with both atypical disease and severe symptoms in humans, such as hypersensitive reactions, nervous system tropism and ocular infections (5).

Immunosuppressed, immunocompromised or individuals with comorbidities may be at a higher risk of sporotrichosis infection. In Brazil, a study identified that 33.8% of cases had high blood pressure and cardiovascular disease, 16.9% had human immunodeficiency virus (HIV), 3.4% had other immunosuppressive conditions such as solid organ transplant, 13.4% had diabetes, 6.1% had alcoholism and 3.3% were pregnant (19). There is limited evidence of specific risk factors associated with severe clinical disease in human sporotrichosis cases. Falcão and others described 782 hospitalisations and 65 deaths in individuals infected with sporotrichosis between 1992 and 2015 in Brazil. 6% of hospitalised cases and 40% of fatal cases were co-infected with HIV (21).

The majority of documented severe sporotrichosis cases have been associated with systemic forms involving the central nervous system in HIV-coinfected patients. A previous review identified 156 cases of sporotrichosis (16.9%) in people living with HIV/acquired immunodeficiency syndrome (AIDS). However, mortality rate could not be calculated in this group of patients since some studies did not report clinical outcomes (19). Furthermore, most studies do not present the immunologic status of the patients, making it difficult to interpret the association between sporotrichosis and immunodeficiency. One fatal case due to S. brasiliensis pulmonary sporotrichosis in an immunocompetent patient from the Northeast region of Brazil has been described (22).

In the USA, the predominant risk factors associated with hospitalizations with sporotrichosis included HIV/AIDS, immune-mediated inflammatory diseases and chronic obstructive pulmonary disease. Other risk factors impacting sporotrichosis prognosis included alcoholism and non-HIV related immunosuppressive conditions, such as those related to organ transplantation, long-term corticosteroid therapy and neoplasia (21).

Cutaneous and lymphocutaneous sporotrichosis usually respond well to antifungal drugs. Treatment is given until all lesions have resolved; typically for 3 to 6 months. However, disseminated disease requires a longer treatment course for a year or more. Patients with immunosuppressive conditions may require lifelong treatment to prevent recurrence (16). In Brazil, a study reported that 85.8% of human cases were cured, 7.5% abandoned treatment, 3.4% died, 1.7% had spontaneous regression and in 0.5% of cases treatment was ineffective (19). It should be noted that it is unclear if sporotrichosis was the primary cause of death in the fatal cases.

One case of human-to-human transmission has been documented, where a child was infected from a lesion on the mother’s arm after frequent close contact. There has also been one probable transplant-associated infection reported in a lung transplant patient (16).

Interim outcomes and recommendations

Although there are evidence gaps affecting the interpretation of the risk sporotrichosis presents to human health in the UK, the HAIRS group has determined that at this stage, there is a very low risk of sporotrichosis from cats to the UK public.

The group determined that, based on the currently available information:

• there is no evidence to suggest that sporotrichosis is currently endemic in the UK feline population, although it should be noted there is no routine surveillance for sporotrichosis in the UK
• cats imported from sporotrichosis endemic countries currently present the greatest risk of sporotrichosis exposure for the UK human population
• individuals in contact with infected cats imported from sporotrichosis endemic countries are those most likely to be exposed to sporotrichosis in the UK
• the impact to human health is dependent on the host’s immunological status, the load and depth of the inoculum and the pathogenicity of the strain, and access to treatment

Based on the above, the HAIRS group makes the following recommendations.

Recommendations for public health professionals

Clinicians should be made aware of the clinical features of sporotrichosis and consider it early in cat owners with non-healing ulcers with or without lymph node involvement, especially if there is a history of feline bites or scratches.

Skin biopsies of a lesion from a suspected human case should be sent to UKHSA’s National Mycology Reference Laboratory (NMRL) (23) for fungal culture, histology with fungal staining, and pan-fungal polymerase chain reaction test when suspected.

Diagnostic laboratories should continue to report any positive Sporothrix species human samples to the UKHSA, as per Health Protection (Notification) Regulations 2010.

Public health agencies should raise awareness amongst those owning or treating cats from endemic areas of the signs and symptoms of feline sporotrichosis to prevent zoonotic transmission, particularly those that may be at a higher risk of developing severe infection (for example immunosuppressed individuals).

Contact should be minimised between a human case and their pet, or an infected pet and their owner, until the end of treatment and skin lesions have healed.

Recommendations for veterinary professionals

The risk of sporotrichosis infection in cats from known endemic countries should be highlighted to veterinary professionals.

Veterinary professionals should be vigilant in taking a travel history when seeing cats with unexplained lesions.

If an imported cat with skin lesions suggestive of a possible sporotrichosis infection is presented to a vet, staff attending the case should use appropriate personal protective equipment to protect from direct contact with any cutaneous or mucosal lesions, disinfect the environment with detergent containing bleach and dispose of potentially contaminated material as clinical waste (for example, by incineration).

Veterinary professionals should consider appropriate sampling (for example, a biopsy of a skin lesion) and submission to the NMRL (23) for testing.

Deceased infected animals should be cremated, not buried, to prevent soil contamination.

Infected animals should be quarantined until the end of treatment and any skin lesions have fully healed, to prevent further transmission. Their environment should be disinfected using detergent containing bleach, and contaminated material associated with the animal appropriately disposed of as clinical waste, once treatment has been completed. 

Evidence gaps identified

What countries are considered endemic for sporotrichosis?

How will climate change, including variations in temperature and precipitation patterns, impact the ecology of places where Sporothrix species inhabit?

How many cats are imported into the UK from endemic countries other than Brazil?

How likely are vets to consider sporotrichosis as a differential diagnosis in imported cats?

What risk factors are associated with increased susceptibility and disease severity in human cases of sporotrichosis?

What proportion of diagnoses are being reported to animal and human health authorities in the UK?

What is the best approach to effective treatment of an animal identified as infected in the UK?

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