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 cupsulatum. In this condition. the central part of the
problems. When blackbirds and crows roost in
suburban areas they become pests. Woodpeckers can
retina (the macula, used in straight-ahead vision)
"hammer" into house siding looking for insects.
becomes inflamed and is damaged as blood vessels
Seagulls can feed at food plants.
grow inside the affected area NEI estimates that four
Many of these birds have more protection by laws
percent of those exposed to the disease have tiny scars
and regulations than the three birds discussed
that put them at risk of developing OHS. An estimated
previously. Special permits may be required to trap
100,000 people have OHS in the rapidly progressive
them or to control them by lethal means. The best
form that can lead to blindness.
approach emphasizes exclusion or modification of
buildings.
Cryptococcosis
Pigeon droppings appear to be the most important
source of the disease fungus, Cryptococcus
HEALTH HAZARDS ASSOCIATED WITH
neoformans, in the environment. The fungus is
BIRDS
typically found in accumulations of droppings in attics,
Health risks from birds are often exaggerated.
cupolas, ledges, water towers, and other roosting and
Nevertheless, large populations of roosting birds may
nesting sites on structures. It has been found in as
present risks of disease to people nearby and pest
many as 84 percent of samples taken from old roosts.
management technicians. The most serious health risks
Even when old and dry, bird droppings can be a
are from disease organisms growing in accumulations
significant source of infection. As many as 50-million
of bird droppings, feathers, and debris under a roost.
colony forming units have been found in a gram of
If conditions are right, particularly if roosts have been
pigeon manure.
active for years, disease organisms can grow in these
The disease is acquired by inhaling the yeast-like
Food may be contaminated by
rich nutrients.
vegetative cells (2-3 microns) of the organism. There
birds, but this risk is usually limited to food
are two forms of cryptococcosis present in humans.
manufacturing or processing plants. When parasite-
The cutaneous form is characterized by acne-like skin
infested birds leave roosts or nests or invade buildings,
eruptions or ulcers with nodules just under the skin.
their parasites can bite, or irritate people.
The generalized form begins with a lung infection, and
spreads to other areas of the body, particularly the
Histoplasmosis
central nervous system. It can be fatal. Like
This systemic fungal disease (mold) is transmitted
histoplasmosis, outbreaks of this disease often occur
to humans by airborne spores from soil contaminated
after building renovation, roost clean-up, or other
by pigeon and starling droppings (as well as from the
actions that disturb the old droppings.
droppings of other birds and bats). [The soil under a
roost usually has to have been enriched by droppings
Other diseases carried or transmitted by birds
for three years or more for the disease organism
affect man to a lesser degree. Psittacosis, pigeon
(Hisroplasma capsulatum) to increase to significant
ornithosis, and toxoplasmosis are normally mild in
levels.] Although almost always associated with soil,
man, however, serious illness or death can occur in
the fungus, in rare instances, has been found in
rare cases. Pigeons and sparrows have also been
droppings alone, such as in an attic. Infection is by
implicated (along with many other species of birds) in
inhalation of the spores which can be carried by wind,
outbreaks of mosquito-borne encephalitis.
particularly after a roost has been disturbed.
Most infections are mild and produce either no
Ectoparasites
symptoms or a minor flu-like illness. The disease can,
Pigeons, starlings, and house sparrows harbor
on occasion, lead to high fever, blood abnormalities,
ectoparasites that can invade buildings. Some of these
pneumonia, and even death. Based on histoplasmin
parasites can bite and irritate. A long list of mites
skin tests given to large numbers of people throughout
infest pigeons, but the northern fowl mite and chicken
the United States, it is thought that about 50 million
mite are usually the main culprits invading buildings
people have had histoplasmosis or been exposed to it.
from nesting and roosting sites. Other pigeon
Each year there are about 500,000 infections, 5,000
ectoparasites that may cause problems inside buildings
people hospitalized, and 800 deaths in the United
States due to histoplasmosis.
are the pigeon nest bug (a type of bed bug), various
The National Eye Institute (NEI) at the National
species of biting lice, the pigeon tick, and the pigeon
Institutes of Health has reported a potentially blinding
fly.
eye condition, called ocular histoplasmosis syndrome
Droppings, feathers, food, and dead birds under
(OHS), that results from infection by the Histoplasma
a roosting or loafing area can also breed flies, fungus
Module Three Chapter 4, Pg 4
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