Emergomyces africanus : a new cause of opportunistic infections in immunocompromised hosts

Emergomyces africanus is a dimorphic fungus reported from South Africa in 2013 (as Emmonsia sp.) as a cause of invasive fungal disease (IFD) in immunocompromised hosts. Herein we describe the clinical features of the disease and the ecological niche of Es. africanus in the environment.

We performed a retrospective case-series of patients diagnosed with Es. africanus infection. 52 cases were diagnosed, the majority were from the Western Cape province. All patients were immunocompromised, most with advanced HIV. Pulmonary and skin disease occurred in 86% and 96% of patients, respectively. Skin lesions were frequently overlooked or misdiagnosed clinically. Half of patients died, a quarter prior to being diagnosed with an IFD.

The failure of clinicians to consider IFD in patients with advanced HIV and skin lesions inspired a prospective study to identify clinical manifestations and risk factors associated with IFD in such patients. We enrolled 39 HIV-infected adult patients in Cape Town with CD4 counts ≤100 cells/µL and widespread cutaneous lesions present ≤6 months, and in whom IFD was considered possible. A diagnosis was made for 34 of 39 patients enrolled. 25 patients had IFDs, including 14 with emergomycosis, and 3 with each of sporotrichosis and histoplasmosis. In 5 additional patients with IFDs the causative pathogens were unproven. Recent antiretroviral therapy initiation and the presence of cutaneous plaques and ulcers were associated with IFD, although skin biopsy remains indispensable for the diagnosis.

Next, we sought to identify the ecological niche of Es. africanus. In 3 investigations using molecular detection, we determined that Es. africanus DNA could be detected in 30% of soil samples collected from the Western Cape, 10% of daily air samples collected in Cape Town, and in none of the tissues of 1402 animals trapped across South Africa. Collectively, this work supports the hypothesis that an environmental reservoir for Es. africanus occurs in soil and that airborne conidia can become inhaled, leading to infection and disease in susceptible individuals.

In conclusion, Es. africanus is an important and serious cause of systemic disease in immunocompromised persons in South Africa. Exposure to infectious propagules from Es. africanus may be common, and further studies are required to identify host, pathogen and environmental characteristics associated with disease. Moreover, education of clinicians and public health officials in South Africa regarding Es. africanus and emergomycosis should be a priority to reduce the burden of morbidity and mortality associated with infection.