Histoplasmosis

Histoplasmosis is an infection caused by a fungus called Histoplasma Capsulatum. The fungus lives in the environment, particularly in soil that contains large amounts of bird or bat droppings. It is also known as Cave disease or Darling’s disease. The fungus has 2 forms; yeast form is the infectious agent in humans. The mycelial form is most commonly found in the environment. Histoplasmosis affects humans in 2 forms pulmonary where the lung involvement is a prominent and disseminated form which occurs in weakened immune system patients where the infection involves other systems like the central nervous system.

Symptoms of histoplasmosis may appear between 3 and 17 days after a person breathes in the fungal spores. In some people, usually, those who have weakened immune systems, histoplasmosis can develop into a long-term lung infection, or it can spread from the lungs to other parts of the body, such as the central nervous system.

The condition is diagnosed based on the history of symptoms, physical examination, and investigations such as direct examination of the scrapings after staining to look for the fungal elements can be done, culture and serology Can be used to confirm the condition. Most of the patients do not require any treatment however some patients may require anti-fungal treatment such as itraconazole or amphotericin B. The condition can be prevented by avoiding exposure to the soil, bat, or bird droppings containing the fungus.

Histoplasmosis: Causes

Histoplasmosis is a condition caused by a fungus named Histoplasma capsulatum.

• Histoplasma capsulatum is the time of fungus which contains two forms sexual multicellular saprophytic mycelia and or asexual single-cell parasitic yeast

• Mycelial form is more commonly found in the environment in the environment

• Yeast form is an infectious agent in the humans

• The infection usually starts after inhalation of the microconidia or the hyphal fragments

• Once the inhalation of the mycelial form happens it gets converted into yeast form which can be triggered by elevated temperatures and increased system level

• Then the yeast cells are phagocytized by the host immune system

• The fungus can survive phagocytosis and when the apoptosis of the infected macrophages happens it spreads the capsulatum fungus infecting the lungs and various other organs depending on the immunity of the patient.

The condition is usually self-limiting in immunocompetent patients.

Histoplasmosis: Symptoms

The patient with histoplasmosis mainly presents with the following symptoms that include −

• Most of the patients with histoplasmosis present with no symptoms

• The condition may present with flu-like symptoms such as cold, cough, fever, chills, headache, body aches, and tiredness

• It also causes a skin condition called tinea pedis that causes itching, burning, and scaling of feet and toes

• The condition presents similar to tuberculosis in weak immune system patients

• The pulmonary type of histoplasmosis may present with cough, chest pain, difficulty in breathing, and fever

• The disseminated type of histoplasmosis results when the infection spreads from the lungs to other parts of the body such as the liver, spleen, bone marrow, and lymph nodes.

• Some patients may present with an infection of the posterior uveal tissue of the eye

Histoplasmosis: Risk Factors

Several factors play an important role in increasing the risk of development of histoplasmosis which includes −

• People more than 50yrs are at increased risk

• People who have a weak immune system as patients with chronic debilitating diseases such as HIV, organ transplant, and cancer patients

• Living in or visiting endemic areas such as the United States, Central and South America, Africa, and Southeast Asia.

• Exposure to bird or bat droppings that are contaminated with Histoplasma capsulatum fungus grows in soil that has been contaminated with bird or bat droppings.

• People who work in construction or demolition, poultry or cave workers who spend time in areas with a lot of bird or bat droppings are at increased risk

• People with chronic lung diseases

Histoplasmosis: Diagnosis

The diagnosis of the histoplasmosis is done as follows −

• Specimens such as sputum, bone-marrow aspirate, peripheral blood, and scrapings from dermal or mucosal ulcers can be taken.

• Direct examination of smears of sputum or pus after staining with Giemsa or Wright stains that shows the presence of fungal elements. The yeast appears as an oval, budding cell measuring 2-4 µm.

• Culture on SDA or brain heart infusion (BHI) agar with cycloheximide and chloramphenicol is inoculated to look for the growth of the fungus. The yeast phase is formed in the culture at 37°C. White cottony mycelial growth containing large (8-20 µm) thick-walled, spherical spores with tubercles or finger-like projections appears at 25°C.

• Serological tests such as Latex agglutination precipitation and complement fixation tests become positive two weeks after infection. An increase in the titer of antibodies indicates a progressive disease.

• Histoplasmin skin test can be done that shows a reaction after treating the skin with the histoplasmosis component. A positive ‘histoplasmosis skin test’ indicates past or present infection, but does not differentiate active and past infections.

Histoplasmosis: Treatment

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Conservative Treatment

Conservative treatment includes −

• The condition is self-limiting in most of the patients

• Itraconazole is one type of antifungal medication that’s commonly used to treat histoplasmosis. Depending on the severity of the infection and the person’s immune status, the course of treatment can range from 3 months to 1 year.

• In severe infections or disseminated cases of histoplasmosis require treatment with other antifungal medications such as fluconazole and amphotericin B. These patients may need intravenous administration of the antifungal drugs.

Histoplasmosis: Prevention

The prevention of histoplasmosis can be done by following the measures that include −

• Avoid projects and activities that might expose you to the fungus, such as cave exploring and raising birds, such as pigeons or chickens.

• Spray contaminated surfaces. Before digging soil or working in an area that could harbor the fungus that causes histoplasmosis, soak it with water. This can help prevent spores from being released into the air. Spraying chicken coops and barns before cleaning them also can reduce your risk.

• Avoid areas with high bird or bat populations.

• Wearing protective clothing while working in a field that involves exposure to soil or bird or bat droppings

• Maintain good hygiene and keep the surrounding areas clean

Conclusion

Histoplasmosis is an infection that is caused by the dimorphic fungus named Histoplasma capsulatum. Histoplasmosis occurs mainly due to the inhalation of the micro or macroconidia of the Histoplasma which in the body develop into yeast form, and multiply to infect the person. The condition presents in 2 forms. The pulmonary form where the lung nodes are involved presents with complaints of cough, chest pain, difficulty in breathing, body aches, fever, and chills. The disseminated form occurs mainly in individuals with weak immune systems where the fungus affects other organs like the liver, spleen, and nervous system.

Histoplasmosis is an infection that is caused by the dimorphic fungus named Histoplasma capsulatum. Histoplasmosis occurs mainly due to the inhalation of the micro or macroconidia of the Histoplasma which in the body develop into yeast form, and multiply to infect the person. The condition presents in 2 forms. The pulmonary form where the lung nodes are involved presents with complaints of cough, chest pain, difficulty in breathing, body aches, fever, and chills. The disseminated form occurs mainly in individuals with weak immune systems where the fungus affects other organs like the liver, spleen, and nervous system.