What Avian Diseases can be Transmitted to Humans?
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Avian Diseases Transmissible to Humans 1
By Jacqueline P. Jacob, Jack M. Gaskin, Henry R. Wilson, and F.
Ben Mather2
Bird-keepers (pet bird owners and poultry producers) should be
aware that some avian diseases can be transmitted to humans. It
is important to note, however, that such diseases are uncommon
enough that they should not discourage bird-keeping. For most
people avian diseases do not pose a serious threat, but
bird-keepers should be aware of them and seek medical assistance
if necessary.
Zoonoses refer to infectious animal diseases that are
communicable to humans. The infectious agents can be protozoal,
fungal, bacterial, chlamydial or viral. Individual susceptibility
and the seriousness of these various microbial infections varies
with age, health status, immune status (immunodeficient or
immunosuppressed), and whether early therapeutic intervention is
sought. The ability of a microorganism to make a person sick
varies with the virulence of the organism, the dose to which the
person is exposed, as well as route of infection.
Chlamydiosis, salmonellosis, arizonosis, and colibacillosis are
the most common of these infections. Chlamydiosis, salmonellosis,
eastern equine encephalitis and avian tuberculosis may be serious
and even life- threatening.
Chlamydiosis
Chlamydia psittaci , an unusual bacteria-like organism, occurs
worldwide and affects more than 100 avian species. It causes a
disease called psittacosis or parrot fever when it occurs in
psittacine birds (curve-beaked, like parrots, parakeets, etc.)and
the disease is called ornithosis when diagnosed in all other
birds or in humans.
In the U.S., chlamydiosis is a major problem with turkeys,
pigeons, and psittacines. In Europe, the main avian species
affected are ducks and geese. Some birds (turkeys) are extremely
susceptible to chlamydiosis, while others (chickens) are more
resistant.
Chlamydiosis is primarily transmitted by inhalation of
contaminated fecal dust and is spread by carrier birds, which act
as the main reservoirs for the disease. The organism is excreted
in both the feces and nasal secretions. Shedding is sporadic and
is usually induced by stress. A carrier state can persist for
years. The organism survives drying, which facilitates oral
spread and allows transmission on contaminated clothing and
equipment. Chlamydiosis can be transmitted bird to bird, feces to
bird, and bird to human. Human to human transmission can occur,
mainly by exposure to patient's saliva.
Chlamydiosis is an occupational hazard for persons working with
psittacines (parrots, parakeets, etc.) and pigeons, or for people
working in turkey slaughter plants and avian diagnostic
laboratories.
The incubation period for chlamydiosis is 4-15 days, although 10
days is most common. In affected birds, diarrhea, coughing, and
ocular and nasal discharges are common signs. There may be a high
mortality rate if the disease is unrecognized or untreated. With
turkeys there is a drop in egg production. In humans,
chlamydiosis manifests itself as a feverish respiratory disease.
There is usually a sudden onset with chills, muscle and joint
pains, headache, cough, loss of appetite, and chest pains.
Complications may result from an enlarged spleen, inflammation of
the heart muscle, and a reduced heart rate.
Affected birds must be treated with chlortetracycline or other
similar broad-spectrum antibiotics for up to 45 days to clear the
infection. Pigeons and turkeys may require long- term flock
therapy to eliminate carriers.
Affected humans are treated with tetracycline for at least 21
days. Because this antibiotic may become irreversibly bound to
certain minerals, the calcium content of food needs to be kept
low during treatment.
In Florida, chlamydiosis is a reportable zoonotic disease for
both health and livestock officials. The Department of
Agriculture and Consumer Services must be notified of any birds
found to be infected with Chlamydia psittaci . If a person is
suspected of having ornithosis, the county public health office
must be notified within 48 hours.
Salmonellosis
There are approximately 200 different serotypes of Salmonella
species. Most animals are susceptible to salmonella infection.
This bacterial disease occurs most frequently in stressed
individuals. Many infections are subclinical. Common clinical
symptoms in all species include diarrhea, vomiting, and a
low-grade fever. Infections -can progress to dehydration,
weakness, and sometimes, especially in the very young or very
old, death. In severe cases there can be a high fever, septicemia
(blood poisoning), headaches, and an enlarged painful spleen.
Focal infections may occur in any organ, including heart, kidney,
joints, meninges (membranes which surround and protect the brain
and spinal cord), and the periosteum (fibrous membrane of
connective tissue which closely surrounds all bones except at the
joints).
The incubation period is 6-72 hours, although 12-36 hours is most
common. Salmonella are transmitted by ingestion of food
contaminated by fecal matter (fecal-oral route). Excretion of the
bacteria commonly varies from a few days to weeks. In some
instances (e.g., S. typhi, typhoid fever) infected persons can
shed bacteria for life. S. enteriditis in avian fecal material is
able to penetrate eggshells, and may be present in uncooked eggs.
In most cases, treatment of salmonellosis simply involves
treatment of the symptoms with fluids and electrolytes.
Antibiotics such as chloramphenicol, nitrofurans, or ampicillin
are only indicated when the bacteria has localized in areas of
the body peripheral to the intestinal tract.
In Florida, salmonellosis is a reportable zoonotic disease for
both health and livestock officials. The Department of
Agriculture and Consumer Services must be notified of any birds
found to be infected with Salmonella species. If a person is
suspected of having salmonellosis, the county public health
office must be notified within 48 hours.
Colibacillosis
Colibacillosis is caused by Escherichia coli infection. E. coli
is a bacteria which normally inhabits the intestinal tract of all
animals. There are a number of different strains, many
species-specific. Not all strains are pathogenic. In poultry, E.
coli infections may cause septicemia, chronic respiratory
disease, synovitis (inflammation of the joints which can lead to
lameness), pericarditis (inflammation of the sac around the
heart), and salpingitis (inflammation of the oviduct). Humans
with colibacillosis usually manifest diarrhea which may be
complicated by other syndromes depending on the E. coli serotype.
These complications may include fever, dysentery, shock, and
purpura (multiple small purplish hemorrhages in the skin and
mucous membranes).
The incubation period is 12 hours to 5 days, although 12-72 hours
is most common. Transmission is via the fecal-oral route.
Colibacillosis is often food- or water-borne.
In most cases, symptomatic treatment (fluids, antidiarrheals) is
all that is required. In more severe infections, antibiotics such
as tetracycline and chloramphenicol may be necessary.
In Florida, colibacillosis is not a reportable zoonotic disease.
Arizona Infections (Arizonosis)
Arizona infections are caused by the bacteria Salmonella arizona
. S. arizona occurs worldwide. It occurs most frequently in
reptiles and birds, but all animals are probably susceptible. The
young are at greatest risk.
In most poultry species S. arizona infection results in reduced
egg production and hatchability. Poults and chicks show weakness,
anorexia, and shivering. Outbreaks in turkeys, chickens, and
canaries can have up to 60% mortality. In humans, diarrhea is
most common. Many infections are subclinical. Septicemia can
occur in immunocompromised individuals.
The incubation period is 6-72 hours, although 12-36 hours is most
common. Transmission is by the fecal-oral route. There is some
transmission through eggs. Infected birds can become long-term
intestinal carriers. Numerous antibiotics reduce case fatality,
but do not clear intestines of the carrier state. S. arizona is
somewhat less hardy than most salmonella but can survive for
months in soil, feed and water.
Arizona infection is not a reportable zoonotic disease in
Florida.
Eastern Equine Encephalitis
Eastern equine encephalitis (EEE) is caused by a RNA virus in the
genus Alphavirus , family Togaviridae. Outbreaks can occur in
commercially raised pheasants, chickens, bobwhite quail, ducks,
turkeys, and emus. Abdominal distress and dysentery are the most
obvious signs.
EEE is mosquito-borne. The virus circulates in a mosquito-bird
cycle in which passerine birds (i.e., song birds such as
swallows, starlings, jays, and finches) are the most common
reservoir. The mosquitoes become infected and feed on birds,
horses, and humans, further spreading the infection. In
pheasants, initial infection is mosquito-borne, but additional
dissemination occurs by pecking and cannibalism.
Most epidemics occur between late August and the first frost.
Cases may occur year-round in areas like Florida which have a
prolonged mosquito season.
EEE usually affects persons under 15 or over 50 years of age. In
adults there is a sudden onset of high fever, headache, vomiting,
and lethargy, progressing rapidly to neck stiffness, convulsions,
spasticity, delirium, tremors, stupor and coma. In children, EEE
is typically manifested by fever, headaches and vomiting for 1-2
days. After an apparent recovery, encephalitis (inflammation of
the brain) is characterized by quick onset and great severity
follows. Retardation or other permanent neurologic consequences
are common in survivors.
EEE is not a reportable zoonotic disease in Florida.
Avian Tuberculosis
Avian tuberculosis is caused by the bacteria Mycobacterium avium
which is closely related to the human and bovine tuberculosis
bacteria. In birds, M. avium causes a chronic debilitating
disease with tubercular nodules. In humans, M. avium infections
can cause local wound infections with swelling of regional lymph
nodes. The infection is most severe in immunocompromised
individuals. M. avium is spread by ingestion of food or water
contaminated by feces from shedder birds. Tuberculous poultry
flocks should be depopulated.
While most Mycobacterium infections are treatable with
antibiotics, M. avium infection is the exception. M. avium is
highly resistant to antibiotics. Surgical excision and lymph node
removal are often necessary to eliminate infection.
In Florida, avian tuberculosis is a reportable zoonotic disease
for both health and livestock officials. The Department of
Agriculture and Consumer Services must be notified of any birds
found to be infected with Mycobacterium avium . If a person is
suspected of having tuberculosis, the county public health office
must be notified within 48 hours.
Histoplasmosis
Certain fungi prefer to grow in soils enriched with avian
manures. Histoplasma capsulatum is one of these. The fungus is
also associated with construction sites and caves. Birds are not
susceptible to infection, but histoplasmosis can affect humans,
dogs, cats, cattle, sheep, horses, and many wild mammals.
The incubation period is 7-14 days. Most cases in humans are
asymptomatic. Disease may be manifested in three forms: acute
pulmonary (most common), chronic cavitary pulmonary, and
disseminated. The acute pulmonary form is influenza-like and
lasts up to several weeks. It is characterized by chills, chest
pain, nonproductive cough, fever, and malaise. The chronic form
occurs in people over 40 and resembles tuberculosis. It is
characterized by a productive cough, pus-like sputum (material
expelled from the respiratory passages), weight loss, and
shortness of breath. The disseminated form occurs in the very
young or the elderly. Lesions include enlarged spleen and liver,
and mucosal ulceration. The disseminated form of histoplasmosis
can be fatal if not treated. Amphotericin B has been used to
treat histoplasmosis.
Transmission occurs by inhalation of spores produced by growth of
the mold. Histoplasmosis is not a communicable disease. The
reservoir is the soil, especially when enriched with droppings
from birds or bats. Wet the area and wear a face mask or
respirator when working in suspect surroundings. Spraying the
soil with a formaldehyde solution has been used to kill the
fungi.
Although this disease is avian-associated, it is not a zoonotic
disease, because the reservoir is soil and not the birds. This
is, however, of little consequence to the unfortunates who become
infected.
In Florida, histoplasmosis is a reportable disease. If a person
is suspected of having histoplasmosis, the county public health
office must be notified within 48 hours.
Cryptococcosis
Another fungus that prefers to grow in soils enriched with avian
manures is Cryptococcus neoformans. The incubation period is
probably weeks. Infections are seen in many mammals, but occur
most frequently in humans, horses, dogs, and cats. Infections are
rare in birds.
Transmission of cryptococcosis is usually by inhalation of this
yeast-like fungus, although it can occasionally occur by
ingestion. Humans can pick up cryptococcosis from exposure to old
pigeon nests or droppings. In humans, cryptococcosis is
manifested as meningitis or meningoencephalitis, and it is
usually preceded by pulmonary infection with cough, blood-tinged
sputum, fever, and malaise. The course of the disease is usually
chronic. There is usually fever, cough, chest pain, and spitting
of blood from the respiratory tract, followed by headache, stiff
neck and visual disturbances.
As with histoplasmosis, this disease is avian-associated, but not
a zoonotic disease because the reservoir is soil and not the
birds.
In Florida, cryptococcosis is not a reportable disease.
Cryptosporidiosis
Cryptosporidiosis is caused by protozoa of the genus
Cryptosporidium . There are three known species, C. baileyi , C.
meleagridis and an unnamed species in quail. Cryptosporidiosis
normally causes respiratory problems in chickens and turkeys. It
can also cause gastroenteritis and diarrhea. In humans, it causes
abdominal pain, nausea, and watery diarrhea lasting 3-4 days. In
immunocompromised people, it can cause severe, persistent
diarrhea with associated malabsorption of nutrients and weight
loss.
The incubation period is 3-7 days, and it is spread via the
fecal-oral route by ingestion of infective oocysts.
In Florida, cryptosporidiosis is a reportable disease. If a
person is suspected of having cryptosporidiosis, the county
public health office must be notified within 48 hours.
Allergic Alveolitis
Allergic alveolitis, also known as pigeon breeder's lung,
budgerigar dander pneumoconiosis, and a variety of other complex
names, is one of the most significant avian zoonotic diseases. It
may occur as an acute, subacute, or chronic problem. Clinical
signs are caused by reduced lung capacity due to a
hypersensitivity reaction to feathers, dander, or fecal dust.
Inflammation of the pulmonary air exchange units (alveoli) is the
inciting lesion.
The acute form of the disease is usually precipitated by an
overwhelming exposure in a previously sensitized individual, such
as that which might occur in cleaning out a pigeon loft. Symptoms
occur within a short time, and include cough, difficult
respiration, fever, and chills. If exposure ceases at this point,
the symptoms resolve and no treatment is necessary. Chronic,
low-grade exposure is more serious, and symptoms may be
mistakenly attributed to a stubborn cold or flu. Affected
individuals have a chronic nonproductive cough, exercise
intolerance, and weight loss. Permanent lung lesions may develop,
including pulmonary fibrosis that reduces gaseous exchange and
lung capacity.
Chronic allergic alveolitis can develop in as little as 2 years,
but usually takes 10-20 years. Patients diagnosed with the
chronic form of the disease may have no choice except to
eliminate all exposure to birds. Exposure to even minute
quantities of feathers, dander, or feces may precipitate a
recurrence of severe respiratory distress. The severity of the
disease can be reduced by wearing face masks while cleaning
cages, cleaning cages daily, bathing pet birds frequently, and
installing air purification systems.
Conclusions
Bird-keepers should be aware that they can contract certain
illnesses from their birds. The frequency of disease transmission
from birds to humans is low, but the very young, the elderly, and
those with compromised immune systems should be cautious.
Many of these diseases are transmitted by ingestion of food
contaminated by fecal matter. Prevention of most of these
diseases, therefore, simply involves proper hygiene and
sanitation. Wearing a face mask to avoid inhaling bird dust is
also recommended.
If you have persistent flu-like symptoms when no one else you
know is affected, see a doctor and mention that you raise birds.
Such symptoms may be indicative of a disease spread from birds to
humans.
Footnotes
1. This document is FACT SHEET PS-23, one of a series of the
Dairy and Poultry Sciences Department, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences,
University of Florida. First printed August 1997. Please visit
the FAIRS Website at http://hammock.ifas.ufl.edu.
2. Jacqueline P. Jacob, poultry extension coordinator with
Dairy/Poultry Sciences, Jack M. Gaskin, associate professor with
Veterinary Medicine-Pathobiology, Henry R. Wilson, professor with
Dairy/Poultry Sciences, and F. Ben Mather, poultry extension
specialist with Dairy/Poultry Sciences, Cooperative Extension
Service, Institute of Food and Agricultural Sciences, University
of Florida, Gainesville, 32611.
Copyright Information
This document is copyrighted by the University of Florida,
Institute of Food and Agricultural Sciences (UF/IFAS) for the
people of the State of Florida. UF/IFAS retains all rights under
all conventions, but permits free reproduction by all agents and
offices of the Cooperative Extension Service and the people of
the State of Florida. Permission is granted to others to use
these materials in part or in full for educational purposes,
provided that full credit is given to the UF/IFAS, citing the
publication, its source, and date of publication.
Acknowledgement
This article by Jacqueline P. Jacob, Jack M. Gaskin, Henry R.
Wilson, and F. Ben Mather is supplied by the World Budgerigar
Organisation (www.worldbudgerigar.org), as part of their
encouraged exchange of research information, and reprinted with
kind permission from American Budgerigar Society Magazine.
