Histoplasmosis: a fungal lung infection seen in travellers

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. MedlinePlus describes the fungus as common in the central and eastern United States, especially around the Ohio and Mississippi River valleys, and also found in parts of Central and South America, Africa, Asia and Australia. Patient.info places the endemic areas in the Americas and the equatorial regions of Africa.

The fungus lives in soil, particularly soil containing large amounts of bat or bird droppings. Patient.info lists it among the endemic fungal pneumonias, alongside coccidioidomycosis and blastomycosis, as distinct from opportunistic fungal infections such as aspergillosis.

A UK Health Security Agency research record describes histoplasmosis as a dimorphic fungal infection that is rare outside endemic pockets, which is why UK clinicians may not think of it first.

MedlinePlus says that if symptoms occur, they usually start between 3 and 17 days after breathing in the spores. They may include fever, cough, tiredness, chills, headache, chest pain and body aches. For most people the symptoms go away within a few weeks to a month, but some people have longer-lasting symptoms, especially if infection becomes severe.

Severe histoplasmosis can become a long-term lung infection, or spread from the lungs to other parts of the body, including the brain and spinal cord, which is called disseminated histoplasmosis. Patient.info lists dissemination to the brain, meninges, skin, liver, kidneys, adrenal glands, heart, eyes and spleen as complications of fungal lung infection.

• Fever, cough, chills, tiredness and body aches a few days to a couple of weeks after exposure.

• Chest pain or breathlessness in more serious infection.

• Weight loss, ulcers or skin lesions in disseminated disease.

• No symptoms at all in most people who breathe in the spores.

MedlinePlus lists people with weakened immune systems, for example from HIV, organ transplant or medicines that weaken the immune system such as chemotherapy and steroids, as well as infants and adults aged 55 and over, as more likely to get a severe infection. Patient.info notes that dissemination tends to occur chiefly in immunocompromised patients.

The UKHSA-listed case report illustrates the UK situation. A woman in her 80s in the Scottish Borders developed disseminated skin and mucosal histoplasmosis after escalating immunosuppression for suspected sarcoidosis and rheumatoid arthritis, despite not having left the UK for more than 20 years. She had travelled to endemic countries long before, which the authors suggest may have been the source decades earlier. This is a single reported case, not a typical presentation, but it underlines the importance of mentioning past travel.

MedlinePlus says your health care provider will ask about symptoms and medical and travel history, examine you, and will likely order a blood, urine or tissue test for signs of the fungus. A chest X-ray or CT scan of the lungs may be ordered.

Patient.info adds that detection of antigen in serum and bronchoalveolar lavage fluid has improved diagnosis of histoplasmosis, and that chest X-ray can show patchy infiltration, nodules or cavitation. In the UK, specialist mycology laboratories support diagnosis, and it helps to tell the clinician about travel even from many years ago.

MedlinePlus says that for some people symptoms go away without treatment, but treatment is needed for severe histoplasmosis in the lungs, chronic histoplasmosis or infection that has spread elsewhere. Treatment is with prescription antifungal medicines, sometimes for 3 months to 1 year.

Patient.info's clinician-facing reference states that itraconazole can be used for immunocompetent patients, amphotericin is preferred for severe infection, and that after successful treatment itraconazole may be used to prevent relapse until immunity recovers. Surgery may rarely be needed for complications. Your specialist chooses the regimen and monitors blood tests and drug interactions.

Because spores are inhaled from disturbed soil and droppings, avoiding enclosed caves with bat guano and activities that disturb contaminated soil in endemic regions reduces risk. The pages read for this guide do not give detailed UK travel advice, so check a travel health service such as TravelHealthPro for current country guidance before travelling.

In the UK, a GP or hospital doctor who suspects histoplasmosis would normally involve infectious diseases, respiratory or microbiology teams on the NHS, with specialist fungal reference testing. Private travel medicine clinics may do initial assessment, but antifungal treatment for significant disease is generally supervised by NHS specialists.