What Is Histoplasmosis?

Histoplasmosis is a fungal infection, usually of the lungs. It is caused by breathing in fungal spores from bird or bat feces in the soil. The fungal spores become airborne when the soil is disturbed, sometimes by construction or clean-up projects.

The infection can be mild or severe. The fungus can spread to many body parts, including the lungs and nervous system. This infection is rare. Only 1,100 cases occurred across the 13 states that reported this condition to the Centers for Disease Control and Prevention (CDC) in 2019.

This article will cover the causes and types of histoplasmosis, the symptoms of histoplasmosis, and how this disease is treated and diagnosed.

Histoplasmosis Symptoms

Histoplasmosis is caused by an infection of the fungus Histoplasma capsulatum. When healthy people are exposed to Histoplasma, they don’t usually develop symptoms. In cases that do cause illness, the symptoms go away on their own within a few weeks to a month.

Those at higher risk of developing severe forms of histoplasmosis include:

• People with weakened immune systems: Those with human immunodeficiency virus (HIV) or AIDS, who have had an organ transplant, or who are taking corticosteroids or tumor necrosis factor (TNF) inhibitors
• Infants and young children
• Adults age 55 and older
• People with lung diseases, including emphysema and bronchiectasis

Histoplasmosis symptoms include:

• Fatigue (extreme tiredness)
• Fever and chills
• Coughing and chest pain
• Headache and body aches
• Joint pain
• Mouth sores
• Red skin bumps, typically on the lower legs

These symptoms show up three to 17 days after contact with the fungus.

Types of Histoplasmosis

Histoplasma can cause fungal pneumonia if it infects the lungs. People with weakened immune systems, like those with HIV, can develop a chronic lung infection with Histoplasma. 

Symptoms of lung infection with Histoplasma include:

• Chest pain and shortness of breath
• Cough, possibly coughing up blood
• Fever and sweating

From the lungs, Histoplasma can travel to lymph nodes and spread to other body parts through the bloodstream. When histoplasmosis spreads throughout the body, it is called disseminated histoplasmosis. Disseminated histoplasmosis causes irritation and inflammation.

If the sac around the heart gets infected and inflamed, it can cause fungal pericarditis and chest pain.

Histoplasmosis can also spread to the nervous system. If the membranes around the brain and spinal cord are infected, it can cause fungal meningitis. The leading symptoms of fungal meningitis are headache and a stiff neck.

If the infection spreads to the blood, it can impact the eyes, called ocular histoplasmosis. It’s a leading cause of vision loss in people between 20 and 40 years old in the United States.

Causes

Bats and birds spread Histoplasma capsulatum in their droppings. Outbreaks can occur when people are exposed to large amounts of disturbed bird or bat droppings and they breathe in fungal spores from the air.

Activities that can lead to histoplasmosis include:

• Digging in soil or chopping wood around bird or bat droppings
• Cleaning chicken coops
• Exploring caves
• Cleaning, remodeling, or tearing down old buildings

Histoplasma can be found in soil in the central and eastern United States. It’s common in areas around the Ohio and Mississippi River valleys. The fungus also lives in Central America, South America, Africa, Asia, and Australia.

Diagnosis

When you get histoplasmosis, you may have no symptoms or mild symptoms. For many, they will resolve on their own. 

If you seek care for histoplasmosis, a healthcare provider will review your medical and travel histories and symptoms, examine your body, and order laboratory tests. Tests may include:

• Blood or urine tests may be able to detect the fungus.
• Chest X-rays or computed tomography (CT) scans will determine how badly your lungs are infected.
• Fluid from your respiratory tract or some lung tissue can be used for a fungal culture test, which may take a few weeks.

Treatment

Many people will get better from a histoplasmosis infection with time and rest. 

Others may get antifungal medications for moderate to severe infections of the lungs, infections that won't go away on their own, or infections that have spread to other parts of the body, including the nervous system.

Some fungal medications that may treat histoplasmosis include:

• Sporanox (itraconazole) for mild-to-moderate conditions
• AmBisome (amphotericin B) for people sick enough to be hospitalized
• Diflucan (fluconazole) for superficial and systemic (whole-body) histoplasmosis

Treatment may last three months to a year or longer, depending on the infection's severity. 

Prognosis 

Studies suggest that most older adults who live in areas with Histoplasma in the soil have been exposed to the fungus at some point during their lifetime. Most people do not know they have been exposed to Histoplasma and do not show symptoms.

One of the most dangerous aspects of histoplasmosis is severe lung infections. Cases of Histoplasma pneumonia can be deadly.

In some people, histoplasmosis hides in the body for months or years. The fungus may show up and cause another infection years later (called a relapse of infection). If the fungus keeps returning, people may need to be on antifungal medications long-term—or even for their entire life.

In cases in which the nervous system is infected with Histoplasma, up to 80% of people respond well to treatment. But about half of these cases relapse.

The infection can be deadly for people with severe, disseminated histoplasmosis that has spread to their central nervous system or caused pneumonia. The histoplasmosis mortality rate in U.S. studies was found to be 2.6% of those admitted to the hospital in one study and 4.9% in another study.

These rates are for people who are already hospitalized with severe illness. The overall mortality rate for histoplasmosis is much lower since many people have less severe forms of infection.

People with severe histoplasmosis infections may have complications, including scarring inside the lung or chest cavity. Scarring and enlarged lymph nodes in the chest impact lung volume or put pressure on the:

• Blood vessels carrying blood to and from the heart
• Heart muscles
• Esophagus

Coping 

Healthy individuals with histoplasmosis may feel under the weather for weeks to months. Getting rest and fluid are the best ways to feel better faster. If you struggle to breathe or can’t shake the infection after a month, talk to a healthcare provider about antifungal treatments.

Coping with histoplasmosis can be more challenging for individuals with weakened immune systems. It may require long-term treatment with antifungal medications that need infusions and can cause side effects. 

But, if you have been diagnosed with histoplasmosis, following your treatment plan as directed by your healthcare provider is vital. The medicines help clear the infection and reduce complications down the road.

Individuals with weakened immune systems are at a higher risk of severe complications from histoplasmosis. Taking care of your overall health by getting enough sleep, eating a balanced diet, and exercising regularly can help to boost your immune system.

Histoplasmosis can be a stressful and isolating experience. Seek emotional support from your healthcare provider, friends, family, or a therapist.

Summary

Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum. The fungus spreads from bird and bat feces in the soil into the lungs. 

The infection can be severe or mild. Symptoms of histoplasmosis include extreme tiredness, fever, chills, coughing, chest pain, headache, and body aches.

The infection is much worse in people with weakened immune systems. From the lungs, the fungus can spread to many parts of the body, including the nervous system. Cases of severe histoplasmosis that require hospitalization can be deadly. 

Healthy people typically clear a histoplasmosis infection on their own with rest and hydration.  Severe cases of histoplasmosis are rare. People with severe histoplasmosis may need antifungal medicine for months or years.