Question: "The town where I live is home to a legion of pigeons, and we have many tales of people getting sick with "bird fever." I am a teacher, and I work in a very old school. I have seen two very large piles of pigeon droppings in the school's attic. I am concerned because I work on the floor directly below the attic, the ceiling of my classroom has cracks in it. Also, the school has recently installed a new air conditioning system in the attic. Am I at risk for catching bird fever?"
Answer: The fungus, Histoplasma capsulatum, can be found in pigeon droppings. Infection by H. capsulatum can cause the disease Histoplasmosis. Three fourths of those who are infected with the fungus exhibit no symptoms or show symptoms of influenza ("flu"). One quarter of those who are infected with the fungus exhibit illness of varying severity, and among these the most common illness is a pneumonia of short duration.
Acute pulmonary histoplasmosis is a respiratory infection that is caused by inhaling the spores of the fungus Histoplasma capsulatum, the fungus that causes histoplasmosis. The infection usually affects the lungs and symptoms can vary greatly. It can sometimes affect other parts of the body, including the eyes, liver, central nervous system, skin, or adrenal glands. For example, "ocular histoplasmosis syndrome" (also known as "presumed ocular histoplasmosis") is a condition that results in impaired vision (affects the eyes). Having a weakened immune system increases your risk for getting this disease (e.g., the very young, very old, or those with medical conditions that lower the body's resistance to infections).
This Histoplasma organism thrives in moderate temperatures and moist environments. It is found in the central and eastern United States, eastern Canada, Mexico, Central America, South America, Africa, and Southeast Asia. It is commonly found in the soil in river valleys. It gets into the soil mostly from droppings from chickens, pigeons, starlings, blackbirds, and bats. Birds are not infected with it because of their high body temperatures, but they do carry it on their feathers. Bats can be infected because they have a lower body temperature than birds and can excrete the organism in their droppings.
To multiply, Histoplasma capsulatum produces small spores called conidia. The conidia of Histoplasma capsulatum are only two millionths of a meter (microns, Ám) in diameter. When these conidia are inhaled, they are small enough that they enter the lungs and start an infection. Many of these infections are easily overlooked because they either produce mild symptoms or none at all. However, histoplasmosis can be severe and produce an illness similar to tuberculosis.
You can get sick when you breathe in spores that the fungus produces. Every year, thousands of people worldwide are infected, but most do not become seriously sick. Most have no symptoms or have only a mild flu-like illness and recover without any treatment.
Acute pulmonary histoplasmosis may happen as an epidemic, with many people in one region becoming sick at the same time. People with weakened immune systems (see Symptoms section below) are more likely to:
Risk factors include traveling to or living in the central or eastern United States near the Ohio and Mississippi river valleys, and being exposed to the droppings of birds and bats. This threat is greatest after an old building is torn down, or when exploring caves.
Most people with acute pulmonary histoplasmosis have no symptoms or only mild symptoms. The most common symptoms are:
Acute pulmonary histoplasmosis can be a serious illness in the very young,
elderly, and people with weakened immune systems, including those who:
Have had bone marrow or solid organ transplants
Take medications to suppress their immune system
Symptoms in these persons may include:
Inflammation around the heart (called pericarditis)
Serious lung infections
Severe joint pain
Exams and Tests
To diagnose histoplasmosis, the doctor needs to find the fungus or signs of the fungus in the body, or evidence that your immune system is reacting to the fungus.
Antibody tests for histoplasmosis
Biopsy of infection site
Bronchoscopy (usually only done if symptoms are severe or you have an abnormal immune system)
Complete blood count (CBC) with differential
Chest CT scan
Chest x-ray (might show a lung infection or pneumonia)
Sputum culture (this test often does not show the fungus, even if you are infected)
Urine test for Histoplasma capsulatum antigen
Most cases of histoplasmosis clear up without specific treatment. Patients
are advised to rest and take medication to control fever.
Your doctor may prescribe medication if you are sick for more than 4 weeks, have a weakened immune system, or are having breathing problems.
When histoplasmosis infection is severe or gets worse, the illness may last
for one to six months. Even then, it is rarely fatal.
Acute pulmonary histoplasmosis can become chronic pulmonary histoplasmosis (which does not go away).
Histoplasmosis can spread from the lungs to other organs through the bloodstream. This type of spread is usually seen in infants, young children, and persons with a weakened immune system.
Acute pulmonary histoplasmosis can get worse over time, or can become chronic pulmonary histoplasmosis (which doesn't go away).
Histoplasmosis can spread to other organs through the bloodstream (dissemination). This is usually seen in infants, young children, and patients with a suppressed immune system.
Call your health care provider if:
You have symptoms of histoplasmosis, especially if you have a weakened immune system or have been recently exposed to bird or bat droppings
You are being treated for histoplasmosis and develop new symptoms
Avoid contact with bird or bat droppings if you are in an area where the spore is common, especially if you have a weakened immune system.