Mayo Clinic Health Library

Histoplasmosis

Updated: 02-08-2012

Definition

Histoplasmosis is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. Histoplasmosis is most commonly transmitted when these spores become airborne, often during cleanup or demolition projects.

Soil contaminated by bird or bat droppings also can transmit histoplasmosis, so farmers and landscapers are at a higher risk of the disease. In the United States, histoplasmosis most commonly occurs in the Mississippi and Ohio river valleys.

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. Effective treatments are available for even the most severe forms of histoplasmosis.

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Symptoms

Several types of histoplasmosis exist. The mildest form produces no signs or symptoms, but severe infections can be life-threatening. When signs and symptoms do occur, they usually appear three to 17 days after exposure and may include:

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

In some people, histoplasmosis can also produce joint pain and a rash. People who have an underlying lung disease, such as emphysema, may develop a chronic form of histoplasmosis that can additionally feature weight loss and a cough that brings up blood. Symptoms of chronic histoplasmosis sometimes can 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, this variety can affect nearly any part of your body, including your eyes, 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.

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Causes

Histoplasmosis is caused by the reproductive cells (spores) of the fungus Histoplasma capsulatum. The spores are extremely light and float into the air when dirt or other contaminated material is disturbed. Even if you've had histoplasmosis in the past, you can still get the infection again. However, if you contract histoplasmosis again, the illness will likely be milder than the initial infection.

The histoplasmosis fungus thrives in damp soil that's rich in organic material, especially the droppings from birds and bats. For that reason, 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.

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Risk factors

The chances of developing histoplasmosis symptoms increase with the number of spores you inhale. Professions with a higher likelihood of spore exposure include:

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

Most at risk of severe infection
Very young children and older adults 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
  • TNF inhibitors, often used to control rheumatoid arthritis
  • Medications that prevent rejection of organ transplants
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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 (ARDS). Histoplasmosis can damage lungs to the point that the air sacs begin filling with fluid. This prevents efficient air exchange and can deplete oxygen levels in the blood.
  • Heart problems. Inflammation of the pericardium, the sac that surrounds your heart, is called pericarditis. When the fluid in this sac increases, it can interfere with the heart's ability to pump blood efficiently.
  • 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 meningitis, an infection and inflammation of the membranes surrounding your brain and spinal cord.
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Preparing for your appointment

You're likely to start by seeing your family doctor. He or she might refer you to a doctor who specializes in infectious diseases. Depending on your symptoms and the severity of your infection, you may also see other doctors, such as a lung specialist (pulmonologist) or a heart specialist (cardiologist).

What you can do

  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Write down key personal information, including any possible exposure to areas with numerous birds or bats.
  • Make a list of all medications, vitamins and supplements that you're taking.
  • Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For histoplasmosis, some basic questions to ask your doctor include:

  • What's the most likely cause of my symptoms?
  • How could I have gotten this infection?
  • What kinds of tests do I need? Do these tests require any special preparation?
  • Will this infection get better on its own, or do I need treatment?
  • What treatments are available, and which do you recommend?
  • What types of side effects can I expect from treatment?
  • Are there any alternatives to the primary approach that you're suggesting?
  • I have other health conditions. How can I best manage them together?
  • Is there a generic alternative to the medicine you're prescribing me?
  • Can I get infected again?
  • Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • When did you first begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • Do you work outdoors?
  • Have you spent an extended time in areas with large populations of birds?
  • Have you spent any time in caves? Or other areas where bats might congregate?
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Tests and diagnosis

Diagnosing histoplasmosis can be complicated, depending on the area of the body being affected. While testing is not usually necessary for mild cases of histoplasmosis, it can be crucial to help choose appropriate treatments in life-threatening cases.

Each type of lab test for histoplasmosis has its limitations. Your doctor may suggest a combination approach to search for evidence of the disease in samples of:

  • Lung secretions
  • Blood or urine
  • Biopsied lung tissue
  • Bone marrow
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Treatments and drugs

Treatment usually isn't necessary if you have a mild case of histoplasmosis. But if your symptoms are severe or if you have the chronic or disseminated forms of the disease, you'll likely need treatment with one or more antifungal drugs. Some of these medications come in pill form, but the strongest varieties are administered intravenously.

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Prevention

It's difficult to prevent exposure to the fungus that causes histoplasmosis, especially in areas where the disease is widespread. Even so, these steps can help reduce the risk of infection:

  • Avoid exposure. If your immune system is compromised, avoid renovation projects that might expose you to contaminated soil. Likewise, cave exploring and raising birds — such as pigeons or chickens — aren't advised.
  • Spray contaminated soil. Before you work in or dig soil that's likely to harbor the fungus that causes histoplasmosis, spray it thoroughly 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.
  • Use an effective face mask. One of the best ways to protect yourself from soil-borne organisms if you must work in contaminated areas or in caves known to harbor bats is to wear a respirator mask. Consult with the National Institute for Occupational Safety and Health to determine which type of mask will provide adequate protection for your level of exposure.
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