Blastomycosis and histoplasmosis are both fungal infections that a person can acquire by breathing in spores from the air. However, the two conditions have different treatment pathways.

The fungus Blastomyces causes blastomycosis. This fungus lives in moist soil with decomposing material such as leaves and wood. In the United States, it typically occurs in midwestern, south-central, and southeastern states.

The Histoplasma fungus causes histoplasmosis. It occurs in soils that contain a large amount of bird or bat droppings. It is most common in the central and eastern states.

These two conditions can cause similar symptoms, but half or more people with exposure to either fungus will not develop symptoms. People with either condition may need antifungal treatments to get rid of the infection.

This article reviews the similarities and differences between these two fungal infections, including their symptoms, causes, treatments, and more.

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Both blastomycosis and histoplasmosis affect the lungs. They have similar symptoms to other lung infections and conditions.

Blastomycosis symptoms

About 50% of people with blastomycosis will show symptoms, which may appear anywhere from 3 weeks to 3 months after exposure to the fungal spores.

Symptoms can include:

In people with weakened immune systems, the infection may spread to other areas of the body, such as the central nervous system, bones and joints, or skin.

Histoplasmosis symptoms

Most people with exposure to Histoplasma will not develop symptoms. If symptoms occur, they may appear within 3–17 days of exposure.

Symptoms can include:

For many people, the symptoms will clear on their own with or without treatment. Those with weakened immune systems may develop a long-term lung infection. The infection may also spread to other areas of the body, such as the central nervous system.

The main difference between the causes of blastomycosis and histoplasmosis is the underlying fungus.

Blastomyces causes blastomycosis, while Histoplasma causes histoplasmosis.

These fungi typically develop in different areas. Blastomyces occurs in moist soil with a lot of decaying leaves and wood in the midwestern, south-central, and southeastern United States. Histoplasma occurs in soil with a lot of bird or bat droppings, often in the central and eastern states.

A person can contract either type of fungus by breathing in fungal spores after the soil becomes disturbed.

While these fungi are most common in the midwestern, southeastern, and eastern United States, a person may come into contact with them outside of these regions.

Blastomycosis and histoplasmosis have similar procedures for diagnosis.

  1. A healthcare professional will perform a physical examination and review of health information. This will likely include asking about medical history, symptoms, and travel history.
  2. If a healthcare professional suspects a fungal infection, they will likely run a urine or blood test to check for the fungus.
  3. They will send the sample to a lab for a culture, which will show whether either fungus is responsible for the symptoms.

For either condition, test results may take a few days to a few weeks to come back, and a positive result will usually be enough to confirm a diagnosis.

A healthcare professional may also order imaging, such as an X-ray or a CT scan, to examine the lungs.

Learn more about tests to diagnose histoplasmosis.

Both blastomycosis and histoplasmosis may require antifungal treatment, but the exact medication can vary.

Histoplasmosis may clear on its own with no need for medication or formal treatment. If a person does need treatment, a healthcare professional will likely prescribe itraconazole. Treatment can last anywhere from 3 months to a year.

Most people who develop blastomycosis will need antifungal medications. For mild to moderate infections, a healthcare professional may prescribe itraconazole. For severe infections, they may prescribe amphotericin B. The treatment may last 6 months to 1 year.

In both cases, the length of treatment depends on the severity of the infection and the immune system’s ability to fight off the infection.

Most people who receive treatment for either condition will recover.

According to the Centers for Disease Control and Prevention (CDC), histoplasmosis has a mortality rate of about 5% for children and 8% for adults. However, these estimates are based on severe cases, so the general mortality rate is likely lower.

The CDC also notes a very low mortality rate for blastomycosis. In the years 1990–2010, the overall age-adjusted mortality rate was 0.21 per 1 million person-years, or about 1,216 deaths.

A person should continue their treatment for the recommended amount of time to help ensure proper recovery from either infection. If treatment does not seem to be helping, they should talk with a healthcare professional.

Learn more about fungal infections.

Blastomycosis and histoplasmosis are similar fungal infections that start in the lungs. A person can develop either condition after inhaling fungal spores from soil or decaying material. Both types of fungus are common in the eastern, southeastern, and midwestern United States.

The two conditions cause similar symptoms and can spread to other areas of the body. They also have similar treatments, and most people will recover from either condition.

Diagnosis will typically involve a physical examination, review of recent travel, and a culture of blood or urine to check for the fungus. Proper treatment can help ensure that a person fully recovers.