Histoplasmosis

1 What Is Histoplasmosis?

Histoplasmosis (also known as "Cave disease," "Darling's disease," "Ohio valley disease," "reticuloendotheliosis," "spelunker’s lung," and "caver's disease") is a disease caused by the fungus Histoplasma capsulatum.

Symptoms of this infection vary greatly, but the disease primarily affects the lungs. Occasionally, other organs are affected; this is called disseminated histoplasmosis, and it can be fatal if left untreated.

Histoplasmosis is common among AIDS patients because of their suppressed immunity. In immunocompetent individuals, past infection results in partial protection against ill effects, if re-infected.

Histoplasma capsulatum is found in soil, often associated with decaying bat guano or bird droppings. Disruption of soil from excavation or construction can release infectious elements, which are then inhaled and settle in the lungs.

2 Symptoms

Most people who have histoplasmosis never have symptoms. Other people may have flu-like symptoms that usually go away on their own.

Symptoms of histoplasmosis include:

Symptoms of histoplasmosis may appear between 3 and 17 days after a person breathes in the fungal spores.

For most people, the symptoms of histoplasmosis will go away within a few weeks to a month. However, some people have symptoms that last longer than this, especially if the infection becomes severe.

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 brain and spinal cord).

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3 Causes

The causative organism of histoplasmosis is a fungus called Histoplasma capsulatum. The fungus is often found in association with bird or bat droppings in the environment.

When the microscopic fungal spores are inhaled, some people develop an illness similar to pneumonia. Not everyone who inhales the spores develops the illness. The spores may become airborne at demolition projects in areas that contain bat or bird droppings. The airborne spores can travel hundreds of feet.

It has been estimated that in the U.S., around 250,000 people are infected each year. Histoplasma capsulatum can be found throughout the world, but it is most commonly located in North and Central America. Within the U.S., it is particularly common in the Ohio and Mississippi River valleys.

In areas where the fungus is common, between 50%–80% of people will show an antibody response to the organism, meaning that they have been exposed to the fungus at some point in their lives.

4 Making a Diagnosis

Clinically, making a diagnosis of histoplasmosis is somewhat difficult.

More severe forms include:

  • A chronic pulmonary form, often occurring in the presence of underlying pulmonary disease
  • A disseminated form, which is characterized by the progressive spread of the infection to extra-pulmonary sites

Oral manifestations have been reported as the main complaint of the disseminated forms, leading the patient to seek treatment, whereas pulmonary symptoms in a disseminated disease may be mild or even misinterpreted as the flu.

Histoplasmosis can be diagnosed with samples containing the fungus taken from sputum (via bronchoalveolar lavage), blood, or infected organs. Histoplasmosis can also be diagnosed by a test for antibodies against Histoplasma in the blood.

It can also be diagnosed through the detection of antigens in blood or urine samples by ELISA or PCR. Antigens can cross-react with antigens of African histoplasmosis (caused by Histoplasma duboisii), blastomycosis, and coccidioidomycosis, paracoccidioidomycosis, and Penicillium marneffei infections.

Histoplasma skin tests indicate whether a person has been exposed, but do not indicate whether they have the disease.

Formal histoplasmosis diagnoses are often confirmed only by culturing the fungus directly. Cutaneous manifestations of a disseminated disease are diverse and often appear as a nondescript rash with systemic complaints.

Diagnosis is best established through urine antigen testing, as blood cultures may take up to six weeks for diagnostic growth to occur, and serum antigen testing often comes back with a false negative before four weeks of disseminated infection.

Histoplasmosis may be divided into the following types:

  • Primary pulmonary histoplasmosis
  • Progressive disseminated histoplasmosis
  • Primary cutaneous histoplasmosis
  • African histoplasmosis

Also known as acute pulmonary histoplasmosis, this is a respiratory infection that is mostly caused by inhaling spores of the fungus Histoplasma capsulatum. This fungus is mostly found in the central and eastern regions of the United States, Mexico, South America, eastern Canada, and Africa. The fungus is commonly found in the soils of the river valleys. It gets into the soil mostly from the droppings of birds and bats. When an individual breathes in the spores produced by the fungus, they tend to get sick. Annually, thousands of people with normal immune systems get infected with this fungus. However, due to their strong immunity, they do not become seriously sick; many of them do not even experience any symptoms or, if there are symptoms, they are mostly mild in nature and abate without need of treatment. Acute pulmonary histoplasmosis can occur as an epidemic, wherein multiple people from the same region become sick at the same time. Individuals with a compromised immune system may get the disease the moment they are exposed to the fungus spores, and if they had the disease previously, it may reoccur or they may experience more of the symptoms, which can become serious in comparison to others with a similar disease.

There are two major factors one should understand about the development of this condition, the first being working in a high-risk occupation, and the second being having an impaired immune system.

  • High-risk occupations: An individual is more likely to be exposed to histoplasmosis if their job exposes them to animal droppings or disturbed soil. Some high-risk occupations include farmers, landscapers, construction workers, demolition workers, pest control workers, and roofers.
  • Impaired immune system: Individuals who have been exposed to histoplasmosis do not usually notice symptoms. However, the risk of a severe infection increases if the individual has an impaired or compromised immune system. Certain medical conditions associated with an impaired immune system are: AIDS or HIV; being very young or old in age; undergoing chemotherapy for cancer treatment; taking immunosuppressant drugs to prevent transplant rejection; taking anti-inflammatory medicines, such as corticosteroids; and taking TNF inhibitors due to certain medical conditions, such as rheumatoid arthritis.

5 Treatment

In the majority of immunocompetent individuals, histoplasmosis resolves without any treatment. Antifungal medications are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease.

Typical treatment of a severe disease first involves treatment with amphotericin B, followed by oral itraconazole. Liposomal preparations of amphotericin B are more effective than deoxycholate preparations. The liposomal preparation is preferred for patients at risk of nephrotoxicity, although all preparations of amphotericin B have a risk of nephrotoxicity.

Individuals taking amphotericin B are monitored for renal function. 

Treatment with itraconazole will need to continue for at least a year in severe cases, while in acute pulmonary histoplasmosis, 6 to 12 weeks treatment is sufficient. Alternatives to itraconazole are posaconazole, voriconazole, and fluconazole.

Individuals taking itraconazole are monitored for hepatic function.

Individuals who suffer from mild symptoms of histoplasmosis can carry out any of the following natural treatments to get relief:

  • Turmeric: Turmeric is known to be loaded with antifungal and antioxidant properties, hence, it is often a wise option when it comes to any mild medical issue. Turmeric has been used for centuries both for cooking and as an herbal remedy. It helps relieve respiratory inflammation, gastrointestinal distress, and other immune system issues. Turmeric helps to treat and protect the body against histoplasmosis.
  • Cloves: Clove is a powerful herb packed with natural antifungal properties which can help to quickly eliminate infections in the lungs and respiratory tract. Adding a few cloves to your meals can be beneficial for the immune system. Another method of taking cloves is to soak them in water overnight and then drink this mixture the next morning; this will keep the body free from fungal infections.
  • Intake of fluids: Whether you are sick or not, it is very important to keep hydrated at all times. Proper intake of fluids on a daily basis will aid in keeping infections at bay. Water helps to flush out the system of any foreign substances and at the same time, it encourages higher metabolic functioning as well as the good health of the immune system. All of this can help naturally eliminate the infection caused by histoplasmosis.
  • Neem leaves: Neem leaves have been used since the Ayurvedic times as an herbal remedy. Neem leaves are considered extremely important if taken along with tea. They help cleanse the body and boost the immune system by eliminating or preventing spores from the fungus from taking hold of the body and causing damage to the respiratory system.
  • Reduce sugar intake: It has been observed that heavily processed foods and artificial sugar lead to an increase in the symptoms of histoplasmosis. Thus, it is wise to adopt a diet that is natural and avoids any kind of packaged food items or junk food. It helps in slowing down and ultimately eliminating the spread of infection.
  • Garlic oil: Garlic as well as its concentrated oil is said to be extremely powerful in fighting against the disease or infection. An active ingredient known as allicin, which is present in garlic, is said to have antifungal, anti-inflammatory, and antimicrobial properties. So, consuming a few cloves of garlic every day can act as a natural remedy for histoplasmosis. 

6 Prevention

There is no vaccine to prevent histoplasmosis.

In areas where the fungus is common, it may not be possible to prevent infection.

Avoiding areas with bird and bat droppings may provide some protection. Wearing a respirator face mask can offer protection for workers in contaminated areas.

Spraying soil with water before working it may help prevent the release of spores in the air. A past case of histoplasmosis can offer some protection against severe disease if you become re-infected.

7 Risks and Complications

The various complications of histoplasmosis include:

  • Pneumonia
  • Stevens-Johnson syndrome
  • Mediastinitis
  • Presumed ocular histoplasmosis syndrome
  • Lung cavity
  • Lymphadenopathy
  • Erythema nodosum
  • Sclerosing mediastinitis
  • Chorioretinitis
  • Zoonosis
  • Aseptic meningitis
  • Broncholithiasis
  • Coin lesion (chest X-ray)
  • Pyrexia of unknown origin

In rare instances, histoplasmosis can become life-threatening or even fatal, so it is very important to get it diagnosed and treated on time. There are many complications that can result from histoplasmosis, including:

  • Issues with heart functioning: The heart finds it difficult to function normally if the area surrounding it becomes inflamed and filled with fluid.
  • Problems with the adrenal glands and hormones: This medical infection can cause damage to the adrenal glands and thus lead to problems concerning hormone production.
  • Acute respiratory distress syndrome: If the lungs are filled with fluid, it can lead to acute respiratory distress syndrome. This in turn would lead to a sudden drop in oxygen in the blood to dangerous levels.
  • Meningitis: Untreated histoplasmosis can lead to a serious medical condition called meningitis. Meningitis is known to occur when the membranes that surround the brain and spinal cord become infected.               
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