Serious health risks arise from diseased organisms that can grow in the nutrient-rich accumulations of bird droppings, feathers, and debris. External parasites also may become a problem when infested birds leave nests and roosts. The parasites then can invade buildings and bite people. Below you will find information on the most common health risks associated with birds.
Histoplasmosis is caused by a fungus (Histoplasma capsulatum). Both humans and animals can be affected. The disease is transmitted to humans by airborne fungus spores from soil contaminated by pigeon and starling droppings (as well as from the droppings of other birds and bats) — especially after a roost has been disturbed. Infection can cause flu-like symptoms, blood abnormalities, pneumonia, blindness and even death.
Pigeon droppings appear to be the most important source of the disease fungus Cryptococcus neoformans in the environment. The fungus is typically found in accumulations of droppings around roosting and nesting sites, for example, attics, cupolas, ledges and water towers. It has been found in as many as 84 percent of samples taken from old roosts. Even when old and dry, bird droppings can be a significant source of infection.
Persons with weakened immune systems are more susceptible to infection. The disease is acquired by inhaling the yeast-like cells of the organism. Two forms of cryptococcosis occur in humans. The generalized form begins with a lung infection and spreads to other areas of the body, particularly the central nervous system, and is usually fatal unless treated. The cutaneous (skin) form is characterized by acne-like skin eruptions or ulcers with nodules just under the skin. The cutaneous form is very rare, however, without generalized (systemic) disease.
Other diseases carried or transmitted by birds affect man to a lesser degree. Psittacosis is normally mild in man; however, serious illness can occur rarely. Pigeons and sparrows also have been implicated (along with many other species of birds) as reservoirs for encephalitis viruses such as West Nile encephalitis virus, which are carried by mosquitoes.