- Chlamydia psittaci infection in birds and its transmission to humans:
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Chlamydia psittaci infection in birds and its transmission to humans:
lnfection with
Chlamydia psittaci is an important cause of systemic illness in companion
birds and poultry (Chlamydiosis).
lnfection can
be transmitted from infected birds to humans, causing illness with pneumonia
(psittacosis).
Chlamydiosis
is a zoonotic disease caused by Chlamydia psittaci. The bacterium has
been isolated from at least 129 avian species and is most commonly identified
in psittacine birds (for example, parakeets, parrots, macaws, and cockatiels).
Among non-psittacine caged birds, infection occurs most frequently in pigeons,
doves, and mynah birds. The incidence in canaries and finches is
relatively low.
The time between
exposure and illness (the incubation period) in caged birds varies from
days to weeks, and may be as short as 3 days. Among infected birds, lalent
infections are common and active disease may occur years after exposure.
Shipping, crowding, chilling, breeding, and other stressful factors may
activate shedding of the infectious agent. Normal appearing birds
may be carriers and intermittent shedders of C.psittaci. The organism is
excreted in the droppings and nasal discharges of infected birds, is resistant
to drying, and can remain ineffective for several months.
The fact that
this organism lives within a celll, instead of on the outside of the cell,
makes it difficult to diagnose and treat by veterinarians and aviculturists.
Another major problem with Chlamydia psittaci or psittacosis involves the
zoonotic potential of the organism. A zoonotic disease is
an infection that can be transmitted from animals to humans. In birds,
psittacosis may present as an upper respiratory infection with nasal and
ocular discharge, diarrhea or as a combination of both. In some cases,
birds may be infected but show no signs. These cases are of concern because
the animals are carriers and shed the organism.
Psittacosis
in humans can result in mild to severe disease. In severe cases, humans
that are infected often have severe fever with night sweats leading to
pneumonia. lt is very important that pet bird owners become aware of this
disease in order to prevent outbreaks from occurring in their aviary or
to protect their pet bird and families. The two routes of transmission
of psittacosis are respiratory and oral. Respiratory transmission insides
the inhalation of infected particles of fecal, ocular, nasal, and respiratory
discharges, and feather dust. Oral transmission includes the ingestion
of food and water contaminated with Chlamydia bearing feces. Parents that
are carriers can infect their nestling via the regurgitated food they feed
the babies.
Chlamydia psittaci
can enter the bird through the respiratory system or the oral cavity. This
usually occurs through infected fecal material that has become airborne,
on aerosolized nasal discharge or from the clothes of a bird owner that
has been exposed. lt is very important that pet bird owners have a post
purchase exam performed on all new birds before they are quarantined or
if quarantined birds become ill. Quarantine procedures should be
in placed at all aviaries/households to prevent introducing infectious
agents into a resident population. Quarantined birds should be maintained
in a room or building with a separate airflow-ventilation system than the
resident population. Quarantine should be for at least 30 days with no
medication given unless prescribes for a specific illness by an avian veterinarian.
This allows quarantined birds to "break" with an illness they may be carrying,
instead of the disease becoming evident when the bird is released. There
is not an adequate diagnostic test available at this time to diagnose Chlamydia
psittaci in a carrier bird. The three day new bird guarantee, based on
a veterinary exam, is useless when screening for C.psittaci. A bird that
is carrying the organism with no obvious signs of infection may break one
month, one year or eight years later with other exposure. All dead birds
should be necropsied by an avian veterinarian to determine the cause of
death. Necropsies are helpful to the aviculturist because they identify
problems or potencial problems in an aviary before they occur. lf a problem
already exists, then treatment and preventive measures may be taken before
any more losses occur. Because of the zoonotic nature of psittacosis, owners
should protect themselves if they have birds that have been diagnosed,
through proper cleaning and management and wearing a face mask. Any bird
owner with high fever and pneumonia like symptoms should inform their physician
that they own birds. Physicians commonly do not associate Chlamydia psittaci
with pneumonia, therefore you may aid in making the right diagnosis.
A prior infection
of psittacosis does not guarantee the bird is immune from reinfection.
Due to the fact that C. psittaci lives "inside" the cells of its host it
does not stimulate high production of antibodies against Chlamydia.
lf you have to
treat birds, doxycycline, a fifth generation tetracycline,
is the drug of choice. Doxycycline or tetracycline derivatives may
he administered in seed, pellets, orally or by injections. All treatments
must be for 45 days. The long treatment period is required because the
intracellular life cycle of the organism makes it difficult to treat. lf
the treatment is not followed for 45 days, the bird may get better, but
probably will become a carrier and shed the organism to other birds and
become ill again. When medicated feed and pellets are used in the
treatment regimen, they should be the only food item offered to ensure
that the bird will receive the appropriate amount of medication. Oral dosing
of medication must be done twice a day. A calcium supplement should be
added to the diet or available in the cage at all times, since tetracycline
hinds with this mineral which may cause a calcium deficiency. lf the bird(s)
being treated become ill during the treatment period contact your avian
veterinarian. The antibiotic injections provide some relief to the
pet bird owner because long acting doxycycline may he administered every
5 to 7 days over a 45 day treatment period. Whatever treatment regime
you and your veterinarian decide on, it must be followed religiously to
be successful. lt is a very costly disease to treat because all forms of
doxycycline are expensive and the treatment period is extensive. Birds
that have been diagnosed with Chlamydia psittaci can be treated. lt is
important for owners to understand this illness to prevent the spread,
of this highly infectious disease. Working closely with your avian veterinarian
will allow you to become knowledgeable of the latest diagnostic testing
and treatment programs. There are research projects looking at more efficient
testing and possible vaccine protection. Until this new information
is available, good aviculture management techniques will hope prevent an
aviary or household from becoming infected with Chlamydia psittaci.
Symptoms of
psittacosis are variable. They depend upon the strain of C.psittaci
with which the bird is infected, the bird's immune system status, species,
age, and the presence of other concurrent infections. Mild outbreaks of
psittacosis may go unnoticed because there will be very few symptoms. Alternatively
there may be very mild respiratory symptoms and diarrhea.
Symptoms are usually
related to respiratory and digestive system involvement.
During the acute
phase those symptoms may including:
