risks from birds are often exaggerated. Nevertheless,
large populations of roosting birds may present the
risk of disease to people nearby. The most serious health
risks arise from disease organisms that can grow in
the nutrient-rich accumulations of bird droppings, feathers
and debris under a roost — particularly if roosts
have been active for years. External parasites also
may become a problem when infested birds leave roosts
or nests. The parasites then can invade buildings and
is caused by a fungus (Histoplasma capsulatum) found
primarily in the areas drained by the Mississippi and
Ohio rivers. 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). The soil under a roost usually has to have
been enriched by droppings for two years or more for
the disease organism to reach significant levels. Although
almost always associated with soil, the fungus has been
found in droppings (particularly from bats) alone, such
as in an attic.
occurs when spores, carried by the air are inhaled —
especially after a roost has been disturbed. Most infections
are mild and produce either no symptoms or a minor influenza-
like illness. On occasion, the disease can cause high
fever, blood abnormalities, pneumonia and even death.
In some areas, including portions of Illinois, up to
80 percent of the population show evidence of previous
infection. Outbreaks of histoplasmosis have occurred
in Central Illinois.
National Institutes of Health (NIH) has reported a potentially
blinding eye condition — presumed ocular histoplasmosis
syndrome (OHS) — that probably results from the
fungus. NIH estimates that 4 percent of those exposed
to the disease are at risk of developing OHS.
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.
histoplasmosis, most cryptococcosis infections are mild
and may be without symptoms. Persons with weakened immune
systems, however, 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. Outbreaks (multiple
cases at a location) of cryptococcosis infections have
not been documented.
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 Saint Louis encephalitis virus, which
are carried by mosquitoes.
mites and other parasites
roosts can harbor parasites that may invade buildings.
Although these parasites can bite and irritate, they
are unlikely to transmit diseases to humans. The northern
fowl mite and chicken mite are usually the main culprits.
Other parasites that may cause problems inside buildings
include the pigeon nest bug and the bat bug (both related
to the beg bug), soft ticks, biting lice and the pigeon
fly. Although most parasites associated with bird or
bat roosts die quickly after the birds or bats leave,
some may live for several weeks.
feathers, food and dead birds under a roosting area
can breed flies, carpet beetles and other insects that
may become major problems in the immediate area. These
pests may fly through open windows or crawl through
cracks to enter buildings. If birds or bats are discouraged
from roosting around buildings, most of the parasites
associated with them will soon die. If the pests are
a problem after birds or bats have been excluded, the
roost area may be treated with a residual insecticide
appropriately labeled by the U.S. Environmental Protection
Agency for control of fleas, ticks, mites and similar
to Health Risks