Histoplasmosis is an infection transmitted by airborne spores that you breathe in when you work in or around soil that contains a fungus called Histoplasma capsulatum. It generally affects your lungs, but may spread to other organs or tissues outside your lungs.
Farmers, landscapers, construction workers and people who have contact with bird or bat droppings are especially at risk of histoplasmosis.
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.
Several types of histoplasmosis exist, ranging from mild to life-threatening. The mildest form produces no signs or symptoms, but severe infections can cause serious problems throughout your body as well as in your lungs. When signs and symptoms do occur, they usually appear three to 17 days after exposure.
Asymptomatic primary histoplasmosis
Acute symptomatic pulmonary histoplasmosis
In some cases, the following may also accompany acute symptomatic pulmonary histoplasmosis:
Arthritis and pericarditis don't mean that the infection has spread outside your lungs. Instead, they develop because your immune system responds to the fungus with an unusual amount of inflammation.
Chronic pulmonary histoplasmosis
When to see a doctor
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.
Histoplasmosis and your lungs
Most often, however, you're not likely to have noticeable signs and symptoms, and the infection clears on its own without treatment. But if your immune system isn't able to eliminate the spores, they can enter your bloodstream and travel to other parts of your body. In that case, you may develop a variety of severe problems that can be fatal if not diagnosed and treated quickly.
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.
Where the fungus lives
It 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.
Birds themselves aren't infected with histoplasmosis — their body temperature is too high — but they can carry H. capsulatum on their feathers, and their droppings support the growth of the fungus. Birds commonly kept as pets, such as canaries and parakeets, aren't affected. And although bats, which have a lower body temperature, can be infected, you can't get histoplasmosis directly from a bat or from another person.
How histoplasmosis infection occurs
You get histoplasmosis when you breathe spores of the fungus Histoplasma capsulatum into your lungs. ...
Anyone exposed to H. capsulatum is likely to become infected. People who inhale a huge number of spores — those who work with heavily infected soil or have close contact with bat droppings, for example — are more likely to develop signs and symptoms.
Most at risk of infection
Most at risk of severe infection
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.
Preparing for your appointment
You're likely to start by first seeing your family doctor or a general practitioner. However, you may then be referred 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).
Here's some information to help you get ready for your appointment, and what to expect from your doctor.
What you can do
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:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.
What to expect from your doctor
Tests and diagnosis
Histoplasmosis can cause a variety of signs and symptoms, many of which resemble those of other illnesses. For that reason, it can be particularly challenging to diagnose. Complicating the matter further is the large number of tests available for detecting the presence of the fungus — each of which has some limitations. These tests include:
Depending on your signs and symptoms and the severity of your illness, your doctor may recommend other tests, such as:
Treatments and drugs
Treatment usually isn't necessary if you have a mild case of acute histoplasmosis. But if your symptoms are severe or you have the chronic or disseminated forms of the disease, you'll likely need treatment with one or more antifungal medications — most often amphotericin B (Fungizone IV) and itraconazole (Sporanox). The specific drug and the length of treatment depend on the type and severity of your illness as well as on your overall health.
In general, one of several formulations of amphotericin B is the initial treatment of choice for people with disseminated histoplasmosis or severe disease. But because these drugs can be toxic to the kidneys and must be administered intravenously, doctors usually switch to itraconazole within a few days to a few weeks, depending on how your condition improves. Corticosteroids are also sometimes given initially if you have severe respiratory disease and difficulty maintaining oxygen levels in your bloodstream.
Itraconazole alone may be effective in mild cases of disseminated histoplasmosis as well as in chronic pulmonary disease. Although itraconazole doesn't work as quickly as amphotericin B, it has fewer side effects and can be taken in pill form. While using this medication, you may experience headache, dizziness, nausea, vomiting or diarrhea, but these symptoms often go away over time. If you have a history of liver or kidney problems, or another lung disease, you'll need to be monitored closely during treatment.
If you're not a candidate for itraconazole or can't tolerate the medication, your doctor may prescribe fluconazole (Diflucan), another antifungal drug. Fluconazole isn't as effective as itraconazole, however, and you're more likely to experience a relapse with this medication.
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:
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.
Last Updated: 2009-12-15
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