Histoplasmosis is an infectious disease caused by inhaling the microscopic spores of the fungus Histoplasma capsulatum. The disease exists in threeforms. Acute or primary histoplasmosis causes flu-like symptoms. Most peoplewho are infected recover without medical intervention. Chronic histoplasmosis affects the lungs and can be fatal. Disseminated histoplasmosis affects many organ systems in the body and is often fatal, especially to people with acquired immunodeficiency syndrome (AIDS).

Histoplasmosis is an airborne infection. The spores that cause it are found in soil contaminated with bird or bat droppings. Sometimes histoplasmosis is called Ohio Valley disease, Central Mississippi River Valley disease, Appalachian Mountain disease, Darling's disease, or Histoplasma capsulatum infection.

Anyone can get histoplasmosis, but people who come into contact with bird andbat droppings are more likely to be infected. This includes farmers, gardeners, demolition and construction workers, bridge inspectors, painters, peopleinstalling or servicing heating and air conditioning units, roofers, buildingrenovators, and cave explorers. Dust suppression measures may help limit exposure. Individuals at risk of developing the more severe forms of the diseaseshould avoid situations where they will be exposed to bat and bird droppings.

The very young and the elderly are more likely to develop severe symptoms, especially if they have a pre-existing lung disease or are heavy smokers. People who have a weakened immune system, either from diseases such as AIDSor leukemia, or as the result of medications they take (corticosteroids or chemotherapy drugs) are more likely to develop chronic or disseminated histoplasmosis.

A simple skin test similar to that given for tuberculosis will tell if a person has previously been infected by the fungus H. capsulatum. Chestx rays often show lung damage caused by the fungus, but do not lead to adefinitive diagnosis because the damage caused by other diseases has a similar appearance. Diagnosis of chronic or disseminated histoplasmosis can be madeby culturing a sample of sputum or other body fluids in the laboratory to isolate the fungus. The urine, blood serum, washings from the lungs, or cerebrospinal fluid can all be tested for a substance that the body produces in response to the infection.

When the spores of H. capsulatum are inhaled, they lodge in the lungswhere they divide and cause injury. This is known as acute or primary histoplasmosis. It is not contagious. Many otherwise healthy people show no symptomsof infection at all. When symptoms do occur, they appear 3-17 days after exposure (average time is 10 days). The symptoms are usually mild and resemble those of a cold or flu: fever, dry cough, enlarged lymph glands, tiredness, and a general feeling of ill health. A small number of people develop bronchopneumonia. About 95% of people who are infected either experience no symptoms or have symptoms that clear up on their own. This creates partial immunity tore-infection. Acute histoplasmosis generally requires no treatment other thanrest. Non-prescription drugs such as acetaminophen (Tylenol) may be used against pain and fever. Avoiding smoke and using a cool air humidifier may ease chest pain.

In some people, spores that cause the disease continue to live in the lungs.In about 5% of infected people, (usually those with chronic lung disease, diabetes mellitus, or weakened immune systems), the disease progresses tochronic histoplasmosis. This can take months or years. Symptoms of chronic histoplasmosis resemble those of tuberculosis. Cavities form in the lung tissue, parts of the lung may collapse, and the lungs fill with fluid. Chronic histoplasmosis is a serious disease that can result in death. Patients with an intact immune system who develop chronic histoplasmosis are treated with the drug ketoconazole (Nizoral) or amphotericin B (Fungizone). In patients with healthy immune systems, alternative therapies can be very successful. These focus on creating an environment where the fungus cannot survive, by maintaininggood health and eating a diet low in dairy products, sugars (including honeyand fruit juice) and foods like beer that contain yeast. This is complemented by a diet high in raw food. Supplements of antioxidant vitamins C, E, and A, along with B complex, may also be added to the diet. Lactobacillus acidophilus and Bifidobacteria will replenish the good bacteria in theintestines. Antifungal herbs, like garlic, can be consumed in relatively large doses and for an extended time.

In patients with suppressed immune systems, chronic histoplasmosis is treatedwith amphotericin B, which is given intravenously. Because of its potentially toxic side effects, hospitalization is often required. The patient may alsoreceive other drugs to minimize the side effects of the amphotericin B. Patients with AIDS must continue to take the drug itraconazole (Sporonox) orallyfor the rest of their lives in order to prevent a relapse. If the patient cannot tolerate itraconazole, the drug fluconazole (Diflucan) can be substituted. Patients with chronic histoplasmosis who are treated with antifungal drugsgenerally recover rapidly if they do not have underlying illness.

The rarest form of histoplasmosis is disseminated histoplasmosis. Disseminated histoplasmosis is seen almost exclusively in patients with AIDS or other immune defects. In disseminated histoplasmosis the infection may move to the spleen, liver, bone marrow, or adrenal glands. Symptoms include a worsening ofthose found in chronic histoplasmosis, as well as weight loss, diarrhea, thedevelopment of open sores in the mouth and nose, and enlargement of the spleen, liver, and adrenal gland. Little is known about the prospects of recoveryfrom disseminated histoplasmosis, because AIDS patients typically have otherinfections that complicate the issue.

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