DISEASE ORGANISMS COMMONLY FOUND IN BIRD AND BAT EXCREMENT
a. The high nutrient content of accumulated bird and bat excrement provides an excellent growth medium for organisms of potential human health concern.
This guide primarily addresses the prevention of two illnesses caused by those organisms: cryptococcosis and histoplasmosis.
b. Cryptococcosis is usually associated with pigeon droppings at elevated roost sites; histoplasmosis with bird and bat droppings on soil under roosts.
However, the infective stages of both organisms may be found in any accumulation of dry droppings and associated organic matter.
c. Personnel should also be aware of the possible dangers of other disease organisms associated with bird and bat excrement, discussed in para 2-2.
2-2. Disease Organisms Associated with Bird and Bat Droppings
a. Mycosis, a fungal infection resulting in disease, is usually incurred by inhaling dusts, especially organic (decaying vegetation) dusts and dusts enriched
with bird or bat droppings, which contain massive amounts of the disease organisms. These fungal organisms are ubiquitous in the environment and
exposure to them is impossible to avoid. However, most humans are resistant to the amounts they encounter during normal activities.
b. The risk of contracting certain of these fungal infections is greatly increased by certain predisposing conditions such as an immunocompromised state
(e.g., HIV infection, immunosuppressing medication, cancer, etc.), antibiotic therapy, surgical trauma, skin injury, and chronic disease. (See also the National
Center for Infectious Diseases.)
c. The fungal disease organisms found in bird and bat droppings are listed below, including the source of the organisms, the methods of contraction, and
the health effects.
(1) Cryptococcosis (Torulosis, European Blastomycosis).
(a) Source. Organic dusts, especially those contaminated with pigeon or bat droppinqs, are the most important source of the fungus, Cryptococcus
neoformans, in the environment. C. neoformans has been found in as many as 84 percent of samples taken from old roosting sites. Up to 50-million colony
forming units of C. neoformans have been found per gram of pigeon droppings.
(b) Contraction. Cryptococcosis is acquired by inhaling the yeast-like vegetative cells of the organism. These cells measure 1-3 microns in diameter and are
(c) Health Effects. Clinical manifestations of pulmonary infection are not characteristic and may be absent. The infection may disseminate to the central
nervous system, resulting in cryptococcal meningitis (inflammation of the membranes of the brain and spinal cord), which is difficult to diagnose and fatal if
not properly, and promptly, treated.
(a) Source. The causative agent of histoplasmosis, Histoplasma capsulatum, a dimorphic fungus (mold), is found in soils throughout the world. It flourishes
by overwhelming other soil organisms when high relative humidity and optimum temperatures are present in soil that has been enriched by accumulated bird
droppings for 3 or more years. It has also been found in bird and bat droppings not in contact with the soil. Once established in soil enriched by bird or bat
droppings, H. capsulatum is difficult to eliminate even after the nutrient source is removed (Krzysik 1989).
(b) Contraction. Humans are infected by inhalation of the spores of this fungus which can be carried by wind and dust.
(c) Health Effects. Most infections produce no symptoms or only a mild influenza-like illness. However, pneumonia, blindness, and even death from a chronic
infection are possible.
(3) Psittacosis (Ornithosis, Parrot Fever).
(a) Source. A rickettsial-like organism, Chlamydia psittaci, causes psittacosis. Approximately 150 cases are reported annually in the United States.
(b) Contraction. This disease is contracted by inhaling C. psittaci which is found in feathers and droppinqs from infected birds. Since the organism becomes
less infectious with time, active roosts are of greatest concern. While the disease most often occurs in bird handlers, persons cleaning up bird excrement
could contract the disease as well.
(c) Health Effects. Psittacosis is characterized by fever, headaches, and muscle pain, with or without obvious respiratory symptoms. Untreated cases,
especially in older patients, can progress to pneumonia and/or generalized toxemia resulting in death.
(4) Other Fungal Diseases. Paracoccidioidomycosis is a serious mycosis among workers in contact with the soil in tropical and sub-tropical regions from
Mexico to Brazil. Although little is known about it at present, it is probably acquired by inhaling soil or fungus laden dust. Other fungal diseases found in soil
and/or decaying organic matter--such as aspergillosis, coccidioidomycosis, blastomycosis, and sporotrichosis--are less likely to cause disease in humans.
d. Unlike the diseases listed above, rabies (a rhabdovirus) is not a fungal disease. However, rabid bats may be encountered during cleanup operations.
(1) Source. Rabies is contracted when the virus-laden saliva of an infected animal is introduced into the body by a bite or scratch (very rarely through
mucous membranes or a fresh break in the skin). Airborne rabies infection has been demonstrated only in one cave in Texas where millions of bats had
roosted for many years.
(2) Contraction. The danger of rabies infection by inhalation is slight, but the danger from handling bats is much greater, especially since infected bats may
be present during a cleanup operation. Cleanup personnel should be cautioned to handle bats only with nets and gloves.
(3) Health Effects. The onset of rabies often begins with a sense of apprehension, headache, fever, malaise and indefinite sensory changes. The disease
progresses to paralysis, throat muscle spasms when attempting to swallow (causing fear of water or hydrophobia), delirium and convulsions. Death is often
from respiratory paralysis. Rabies can be prevented by vaccination during the disease's incubation period. Once symptoms appear, however, death is
almost always inevitable.
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