Overview

Histoplasmosis is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. The infection is most commonly spread when these spores are inhaled after taking to the air, such as during demolition or cleanup projects.

Soil contaminated by bird or bat droppings also can spread histoplasmosis, putting farmers and landscapers at a higher risk of the disease. In the United States, histoplasmosis commonly occurs in the Mississippi and Ohio River valleys, though it can occur in other areas, too. It also occurs in Africa, Asia, Australia, and in parts of Central and South America.

Most people with histoplasmosis never develop symptoms and aren't aware they're infected. But for some people — primarily infants and those with compromised immune systems — histoplasmosis can be serious. Treatments are available for even the most severe forms of histoplasmosis.

Symptoms

The mildest forms of histoplasmosis cause no signs or symptoms, but severe infections can be life-threatening. When signs and symptoms occur, they usually appear three to 17 days after exposure and can include:

  • Fever
  • Chills
  • Headache
  • Muscle aches
  • Dry cough
  • Chest discomfort
  • Fatigue

Some people with histoplasmosis also get joint pain and a rash. People who have a lung disease, such as emphysema, can develop a chronic form of histoplasmosis.

Signs of chronic histoplasmosis can include weight loss and a bloody cough. The symptoms of chronic histoplasmosis sometimes mimic those of tuberculosis.

Severe histoplasmosis

The most severe variety of histoplasmosis occurs primarily in infants and in people with compromised immune systems. Called disseminated histoplasmosis, it can affect nearly any part of your body, including your mouth, liver, central nervous system, skin and adrenal glands. If untreated, disseminated histoplasmosis is usually fatal.

When to see a doctor

Contact your doctor if you develop flu-like symptoms after being exposed to bird or bat droppings — especially if you have a weakened immune system.

Causes

Histoplasmosis is caused by the reproductive cells (spores) of the fungus Histoplasma capsulatum. They float into the air when dirt or other material is disturbed.

The fungus thrives in damp soil that's rich in organic material, especially the droppings from birds and bats. It's particularly common in chicken and pigeon coops, old barns, caves, and parks.

Histoplasmosis isn't contagious, so it can't be spread from person to person. If you've had histoplasmosis, you can get it again. However, if you do get it again, the illness will likely be milder the second time.

Risk factors

The chances of developing histoplasmosis symptoms increase with the number of spores you inhale. People more likely to be exposed include:

  • Farmers
  • Pest control workers
  • Poultry keepers
  • Construction workers
  • Roofers
  • Landscapers and gardeners
  • Cave explorers
  • Demolition workers

Most at risk of severe infection

Children younger than age 2 and adults age 55 and older have weaker immune systems, so they're more likely to develop disseminated histoplasmosis — the most serious form of the disease. Other factors that can weaken your immune system include:

  • HIV or AIDS
  • Cancer chemotherapy
  • Corticosteroid drugs, such as prednisone
  • Tumor necrosis factor inhibitors, often used to control rheumatoid arthritis
  • Medications that prevent rejection of organ transplants

Complications

Histoplasmosis can cause a number of serious complications, even in otherwise healthy people. For infants, older adults and people with compromised immune systems, the potential problems are often life-threatening.

Complications can include:

  • Acute respiratory distress syndrome. Histoplasmosis can damage lungs to the point that the air sacs begin filling with fluid. This prevents good air exchange and can deplete the oxygen in your blood.
  • Heart problems. Inflammation of the sac that surrounds your heart (pericardium) is called pericarditis. When the fluid in this sac increases, it can interfere with the heart's ability to pump blood.
  • Adrenal insufficiency. Histoplasmosis can harm your adrenal glands, which produce hormones that give instructions to virtually every organ and tissue in your body.
  • Meningitis. In some cases, histoplasmosis can cause this inflammation of the membranes surrounding your brain and spinal cord.

Prevention

It's difficult to prevent exposure to the fungus that causes histoplasmosis, especially in areas where the disease is widespread. But taking the following steps might help reduce the risk of infection:

  • Avoid exposure. 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 you dig soil or work 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.
  • Wear a respirator mask. Consult the National Institute for Occupational Safety and Health to determine which type of mask will provide protection for your level of exposure.

Feb. 20, 2020
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  2. Histoplasmosis. Centers for Disease Control and Prevention. https://www.cdc.gov/fungal/diseases/histoplasmosis/index.html. Accessed Dec. 13, 2019.
  3. AskMayoExpert. Histoplasmosis. Mayo Clinic; 2019.
  4. Azar MM, et al. Clinical perspectives in the diagnosis and management of histoplasmosis. Clinical Chest Medicine. 2017; doi:10.1016/j.ccm.2017.04.004. Accessed Dec. 13, 2019.
  5. Kauffman CA. Diagnosis and treatment of pulmonary histoplasmosis. https://www.uptodate.com/contents/search. Accessed Dec. 13, 2019.
  6. Histoplasmosis: Protecting workers at risk. Centers for Disease Control and Prevention. https://www.cdc.gov/niosh/docs/2005-109/. Accessed Dec. 17, 2019.
  7. Histoplasmosis. Merck Manual Professional Version. https://www.merckmanuals.com/professional/infectious-diseases/fungi/histoplasmosis. Accessed Dec. 13, 2019.

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