Histoplasmosis in Africa is under-recognized and under-reported
January 22 2018
Despite being an AIDS-defining infection, much basic information about histoplasmosis is lacking, including accurate incidence/prevalence rates, morbidity/mortality rates, and outcomes. This is due to haphazard reporting in regions with more basic laboratory and imaging facilities, and confusion with diseases such as TB. Culture is exceptionally slow (1-6 weeks) and requires a biosafety level 3 laboratory.
Dr Rita Oladele and colleagues in Lagos and Manchester systematically reviewed the available scientific literature for histoplasmosis in Africa. 470 cases (247 dubosii and 185 capsulatum cases) were identified from 32 countries from published cases and series, but this is thought to be a great underestimation. A small number of dubosii cases (previously called ‘African histoplasmosis’) were seen in HIV positive patients, with different manifestations from non-immunocompromised patients.
The country to report the most cases was Nigeria, with 124 cases. Studies found positive skin test reactions to the antigen histoplasmin among ~3% of community members and ~5–10% of hospital patients, although much higher prevalence (~35%) was seen among rural populations. N.B. skin testing measures whether a person has ever had an infection (i.e. not only current infections).
To improve detection rates and outcomes, clinicians should be aware of the following:
- Populations at particular risk of the disease include cave guides, sawmill workers and those who have recently come into contact with chicken coops. The CDC provides guidance on how to minimise exposure.
- Lesions can be distinguished from malignancies by histological examination. Serology for anti-Histoplasma antibodies is useful in cases with low fungal load, as found in sub-acute and chronic histoplasmosis.
- In the absence of modern diagnostics, some clinical signs are suggestive of either histoplasmosis or TB. Histoplasmosis is more often associated with hepatosplenomegaly (and high LFTs), diarrhoea, skin lesions, GI symptoms or immune suppression; TB is more often associated with weight loss and nights sweats.
- The Infectious Diseases Society of America recommends prophylaxis with itraconazole for as long as the CD4 count remains below 150/mm3 in highly endemic areas – these have yet to be defined in Africa.
- Treatment induction with IV amphotericin B or oral itraconazole.
Picture courtesy of the CDC.