What is histoplasmosis and what causes it?
Histoplasmosis is an infectious disease of the lungs caused by a fungus called Histoplasma capsulatum. The infection sometimes can spread to other parts of the body.
This Histoplasma organism thrives in moderate temperatures and moist environments. Droppings from chickens, pigeons, starlings, blackbirds, and bats support its growth. 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, µm) 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.
How can we prevent histoplasmosis?
Prevention of histoplasmosis relies on avoiding exposure to dust in a contaminated environment. Before anyone cleans chicken coops or other contaminated soil, spraying with water is advisable to reduce dust. Decontamination with 3% formaldehyde has been shown to be effective.
However, formaldehyde solutions should be used with caution since this chemical may cause adverse health effects following inhalation, ingestion, or skin or eye contact.
Persons working in contaminated areas should use protective clothing such as gloves and coveralls. They should also use a respirator equipped with a high efficiency particulate air (HEPA) filter that is capable of filtering particles down to two microns in size. Such respirators are suitable as long as the occupational exposure limit for formaldehyde is not exceeded. For major clean up operations of prolonged exposure, a powered air purifying or supplied air respirator may be necessary.