HEALTH HAZARDS ASSOCIATED WITH BIRD AND BAT DROPPINGS|
Health risks from
birds and bats 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 or bats leave roosts or nests. The
parasites then can invade buildings and bite or irritate people.
"After a small group of students raked and swept a 20-year
accumulation of dirt, leaves, and debris in a middle school’s courtyard on Earth
Day–1970, nearly 400 people (mostly students) developed histoplasmosis. (92) The
school’s forced-air ventilation system, which had fresh air intakes in the
courtyard, was implicated as being primarily responsible for spreading
contaminated air throughout the school. Results of the outbreak investigation
showed that a few students developed histoplasmosis despite being absent from
school on the day when the courtyard was cleaned. This finding suggests that
exposures to spore-contaminated dust continued for a day or more after cleaning
of the courtyard was stopped."(NIOSH
- National Institute of Safety and Health)
Histoplasmosis is caused by a fungus (Histoplasma capsulatum). 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.
Infection 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.
The 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.
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.
Like 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 have not been documented.
Other diseases carried or transmitted by birds affect man to a lesser degree.
Psittacosis and toxoplasmosis are normally mild in man; however, serious illness
or death does occur rarely. Pigeons and sparrows also have been implicated
(along with many other species of birds) as sources of encephalitis viruses
carried by mosquitoes.
Bats and disease
Bats are associated with a few diseases that affect people, such as rabies
and histoplasmosis. Rabies is a dangerous, fatal disease, but only about 5
percent of bats submitted for testing are infected with the rabies virus. In
recent years, there has been increased concern about the risk of rabies
transmission following contact with bats. If an injured or ill bat is found in
or around a structure, it should be removed. Because most bats will try to bite
when handled. Contact our Orlando bat experts. If a bat has bitten or scratched
someone, capture the bat without touching it with your hands and without
crushing its head. If the bat is dead, refrigerate it (DO NOT freeze) and then
contact your local health department immediately for instructions.
The incidence of histoplasmosis being transmitted from bat droppings to
humans is not thought to be high. Nevertheless, fresh bat droppings (unlike
fresh bird dropping) can contain the histoplasmosis fungus. Bat droppings do not
need to come into contact with soil to be a source of the disease.
Ticks, mites and other parasites
Bird or bat 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.
Droppings, 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, the roost area should be treated with a residual
insecticide appropriately labeled by the U.S. Environmental Protection Agency
for control of fleas, ticks, mites and similar pests.
Removal and cleanup of bird and bat droppings
If there is a small accumulation of droppings from a few birds or bats, it
can be cleaned up with soap and water. If large quantities of bird or bat
droppings are present, contact our Orlando Animal Control office for advice.
Our employees follow certain precautions to minimize risk from disease
organisms in the droppings:
- Cleanup should be done by Wildlife Patrol.
- We wear a respirator that can filter particles as small as 0.3 microns.
- We wear disposable protective gloves, hat, coveralls and boots.
- During the cleanup, seal heating and cooling air ducts or shut the
- Moisten the droppings with a Disinfectant to keep spores from becoming
airborne and keep them wet.
- Put droppings into sealed plastic garbage bags 3 mil thick.
- When finished and while still wearing the respirator, remove protective
clothing and place it in a plastic bag.
- Modify the structure to prevent birds or bats from reestablishing the