Histoplasmosis in Africa: Current perspectives, knowledge gaps, and research priorities

Background

Histoplasmosis is a chronic granulomatous disease caused by the thermally dimorphic fungus Histoplasma capsulatum. The 2 variants Histoplasma capsulatum var. capsulatum (Hcc) and Histoplasma capsulatum var. duboisii (Hcd) causes infection in humans and commonly termed classical or American histoplasmosis and African histoplasmosis, respectively. Histoplasma capsulatum var. farciminosum (Hcf) affects equines. In recent times, there have been heightened sensitization on fungal infections such as histoplasmosis in Africa, aimed at improving awareness among relevant stakeholders, particularly healthcare workers. This effort is expected to be paralleled with increased detection of both classical and African histoplasmosis, which has remained underdiagnosed over the years. In this narrative review, we describe the current perspectives of histoplasmosis in Africa, identify knowledge gaps, and suggest research priorities.

Methods

A PubMed, Google Scholar, and Africa Journal Online (AJOL) literature search was conducted for studies on histoplasmosis in Africa between 2000 and 2020. Histoplasmosis essays in medical mycology textbooks were also consulted. This narrative review was prepared from the data gathered.

Findings

In the past 2 decades, histoplasmosis in general has seen a relative increase in case detection in some Africa countries, probably attributable to the gradually increasing medical mycology advocacy efforts in Africa. Histoplasmosis cases are dominated by African histoplasmosis mostly in Western and Central Africa, while classical histoplasmosis is more common in Southern and Northern Africa. Although both classical and African histoplasmosis are common in Africa, the latter is more restricted to Africa, and cases outside the continent usually have a travel history to the continent. Despite the clinical and laboratory difference between African histoplasmosis and classical histoplasmosis, it is not straightforward to distinguish them. The typical manifestation of African histoplasmosis is the appearance of lesions affecting the skin, bones, and lymph nodes and unusually linked to human immunodeficiency virus (HIV)/AIDS. By contrast, classical histoplasmosis mostly affects the lungs and is often associated with immunosuppression, mainly HIV/AIDS. The present perspectives of histoplasmosis in Africa highlight unclear details on the true burden, strain diversity, infection route and genetic basis of African histoplasmosis, availability of specie-specific diagnostic tools, and compliance with recommended antifungal therapy. These knowledge gaps represent research questions that require scientific exploration.

Conclusions

Despite a subtle increase in identifying histoplasmosis cases in Africa, it remains underdiagnosed and neglected in some parts of the continent. Increasing awareness and training among healthcare workers, bridging diagnostic and therapeutic gaps, and encouraging more research in Africa are crucial to improve the current perspectives of histoplasmosis in Africa.

Incidence and Trends in Immune Reconstitution Inflammatory Syndrome Associated With Histoplasma capsulatum Among People Living With Human Immunodeficiency Virus: A 20-Year Case Series and Literature Review

BACKGROUND

Histoplasmosis is among the main acquired immunodeficiency syndrome (AIDS)-defining conditions in endemic areas. Although histoplasmosis has a worldwide distribution, histoplasmosis-associated immune reconstitution inflammatory syndrome (IRIS) in people living with human immunodeficiency virus (PLHIV) is rarely reported.This study aimed to describe the incidence and features of histoplasmosis-associated IRIS in a cohort of PLHIV.

METHODS

A retrospective multicenter study was conducted in French Guiana from 1 January 1997 to 30 September 2017. The target population was represented by PLHIV who presented an episode of histoplasmosis within 6 months after antiretroviral therapy initiation. We used a consensual IRIS case definition, submitted to the agreement of 2 experts. Each case was described using a standardized questionnaire, and all patients gave informed consent.

RESULTS

Twenty-two cases of histoplasmosis-associated IRIS were included (14 infectious/unmasking and 8 paradoxical), with an overall incidence rate of 0.74 cases per 1000 HIV-infected person-years (95% confidence interval, 0.43-1.05). Mean age was 40.5 years. The ratio of males to females was 1:4. Median time to IRIS was 11 days (interquartile range 7-40 days) after antiretroviral therapy initiation. The main clinical presentation was fever, without any specific pattern, and disseminated disease. We reported 2 severe cases and partial or complete recovery at 1 month was the rule. Twenty-two cases were identified in the literature with similar characteristics.

CONCLUSIONS

Histoplasmosis-associated IRIS incidence was low but generated significant morbidity in PLHIV. In endemic areas, screening for latent or subclinical histoplasmosis should be implemented before antiretroviral therapy initiation.