INFECTION IN BIRDS
By Dr Colin Walker BSc, BVSc, MRCVS, MACVSc
Have you ever had a young Cockatiel, Budgerigar or
other species of parrot with a squinty red eye and dirty cere? If so, almost
certainly the cause was Chlamydophila psittaci.
Nature of the Disease
Chlamydophila psittaci are the organisms that cause the disease called Psittacosis
(or sometimes Ornithosis, Chlamydiosis or Chlamydophilosis). Infection can
cause a variety of problems and symptoms but usually it is the respiratory
system that is affected. Infection is very common. Chlamydophila psittaci
are single-celled organisms that are carried within the system of the vast
majority of parrots and pigeons virtually all the time. Certain other birds,
including chickens, can also be infected.
Most aviaries have one or more resident strains of Chlamydophila. Most birds
are passively infected by their parents at a young age but, rather than becoming
sick, simply mount an immune response and start to form a natural immunity
to the organism. Ongoing low-grade exposure through early life tends to reinforce
and strengthen the birds’ developing natural immunity. Most parrots and
pigeons by the time they are six months of age, and almost all individuals
by the time they are 12 months of age, have developed a sufficiently strong
natural immunity to protect them from disease. For this reason, disease in
birds older than 12 months is uncommon. Stress in the form of bad management
practices or a poor aviary environment puts any natural immunity that the birds
have developed to the test.
Disease occurs in one of two ways:
1. When birds come under stress and the natural immunity that they have developed
is not strong enough to protect them.
Disease will occur most commonly in this situation in young birds. Young birds
simply have not lived long enough to form the natural immunity of an older
bird. As a result, it takes less stress to trigger a disease outbreak. Overcrowding,
low hygiene and a poor aviary environment are all common causes of stress.
2. When birds come in contact with a new harmful Chlamydial strain to which
they have no immunity.
Birds develop an immunity to the Chlamydial strains in their aviary. New birds
can bring in a new Chlamydial strain, starting a disease outbreak. Similarly,
an introduced bird may become unwell because it comes in contact with a resident
aviary strain that it might not have encountered before. Birds that have been
in a pet shop or market are particularly at risk. Often these birds are young
with a low natural immunity. There are many inherent stresses associated with
pet shops. Apart from transport and the change of housing, there is usually
more noise, a higher degree of interference and higher stocking densities.
At the same time, birds from many backgrounds come into intimate contact, offering
an increased risk of disease exposure.
Signs to Look For
Chlamydophila psittaci, which typically causes an upper respiratory infection,
targets the bird’s sinuses, membranes around the eyes and lining the
eyelids (conjunctiva) and the upper windpipe. Birds have large sinuses compared
to mammals. Draw an imaginary line across a bird’s head level with its
eyes. In most bird species there is no brain between this line and the base
of the beak. This area is occupied by sinuses.
Sinuses are bony cavities lined by a membrane similar to that in our nose.
Like the membrane in our nose, when infected, the membrane lining the sinus
weeps inflammatory fluid. The sinuses are interconnected through narrow ducts
and ultimately drain under the cere and down into the slot in the roof of the
bird’s mouth (choana). Often fluid forms in a sinus quicker than it can
drain away, which results in the sinus filling with fluid. Because the outer
walls of a bird’s sinus system are soft tissue (unlike bone in mammals),
build-up of the fluid causes the sinus to bulge. As the fluid drains from the
swollen sinus, some will trickle out through the cere, causing sneezing and
matting of the feathers at the beak base. As fluid flows into the choana, it
can become blocked, resulting in the bird being unable to breathe through its
cere and having to open its beak to breathe in an action that looks like panting.
Usually Chlamydophila psittaci confine themselves to the upper respiratory
tract, however, the organism has the potential, particularly in run-down or
poorly managed birds, to cause internal disease. The spleen, liver, bowel,
lungs, air sacs and genitals can all be affected. These birds become quiet,
lose weight, develop green diarrhoea and can have trouble breathing. Once the
disease is established, significant numbers of birds will die if treatment
is neglected. Older birds whose genitals are affected can display a variety
of reproductive problems.
Is It Really Chlamydophilosis?
Often the signs displayed by the birds are very suggestive of the problem.
However, a variety of tests and diagnostic methods is available to diagnose
the disease. Each method has its own advantages, limitations and inherent costs.
Your veterinarian can advise as to which one is appropriate for your situation.
In live birds, there is a test that can detect the organism in either droppings,
eye and cere discharges, or tissue samples. Another test can detect the presence
of either previous or current infections from a blood sample. Birds that die
often display visible changes at autopsy that are also very suggestive of the
problem (eg a large spleen or liver and inflamed air sacs). If needed, tissue
samples can be collected during autopsy and examined under a microscope, where
special stains actually enable the organism within the bird’s cells to
How to Manage an Outbreak
The drug of choice to treat Chlamydophilosis is an antibiotic called doxycycline.
This is available as an injection, an oral paste, in tablet form and also
as a water-soluble powder. In theory, if birds are treated continuously for
30–45 days, it is possible to completely clear Chlamydophila from their
system. Because of the inconsistent way that many birds drink, if the aim
is to eradicate the organism from an individual, then the only realistic
approach is to individually dose each bird daily either orally (with either
a tablet or paste or with the antibiotic in solution via a crop needle) or
by injection. Most injections last 2–3 days, requiring two to three
visits to the veterinarian weekly for approximately six weeks. Although treating
to eradicate the organism from a single bird actually appears to be the logical
way to go, this is not always so. If the organism is cleared, this means
that the bird will have no further ongoing exposure and its natural immunity
will quickly wane. If this bird then comes in contact with the organism again
(and this is very likely if it comes in contact with another bird), it will
be extremely vulnerable to infection.
Because Chlamydophila infection often appears as an eye problem, with the birds
presenting with a red squinting discharging eye, some fanciers attempt treatment
with antibiotic eye drops. Because the disease is systemic, treating the eye
only is of limited value and a much better response can be expected if antibiotics
are given orally. Bathing the eye with warm water or saline will, however,
remove bacteria and their toxins as well as dried discharges. This will not
only make the bird more comfortable but hasten the healing process.
Chlamydophila psittaci do have the potential to infect people. Fortunately,
most people are naturally resistant to infection. However, people whose own
health is already compromised are more susceptible. Birds are important but
people are much more important. Therefore, if a person at risk is involved
with a bird’s care, often the decision is made to treat to eradicate
the organism or dispose of the bird.
A recent study in America conducted over 12 months monitored the health of
18 million bird fanciers. During this time, 78 people caught the disease. This
represents one in approximately 231,000. This is obviously a very low incidence
rate so although there is a risk, this risk needs to be kept in perspective.
Often birds are treated until they are well and then treatment is withdrawn.
How long they need to be treated depends on the initial severity of infection
and their response to treatment but treatment times of 7–14 days are
Obviously, when a single pet bird is infected, just that bird is treated. However,
what should one do if an outbreak occurs in an aviary? Basically, the answer
depends on the number of birds affected, although factors such as whether or
not the birds are breeding will also influence the decision. If only a small
number of birds are clinically affected, then these are separated and treated,
usually only until they are clinically well.
In the meantime, it is important to provide good ongoing care, try to identify
and correct any predisposing stresses, and closely monitor all other birds.
Chlamydophila psittaci can survive in droppings for about seven days, so a
thorough clean of the aviary will decrease its exposure to the birds. It is
always a good idea to have a veterinarian check not only the sick birds but
also the other birds. This will identify any concurrent disease that may be
present, in particular, parasitism. A veterinarian can also review the birds’ nutrition
and general care.
If a significant number of birds become infected or there is evidence of spreading
infection so that a new bird becomes clinically sick every few days, then a
flock treatment is usually recommended. Often the fact that birds continue
to become unwell is not so much the result of the organism spreading from bird
to bird but rather the result of all the birds having been under the same stress
and ‘breaking down’ at the same time. This is why it is so important
to review aviary management and environment when faced with a disease outbreak.
Any flaw here will need to be identified and corrected. If this does not occur,
response to even correct medication will be poor or the condition will quickly
recur when medication is withdrawn. Usually, when treating flocks, a single
course of medication is given, often of 7–14 days, although occasionally ‘pulse’ treatments
are given, eg three days every 2–3 weeks. This tends to keep the Chlamydophila
under control while still allowing the birds some exposure to it. With ongoing
good care, this enables the birds’ natural immunity to rise with time.
Often, after several courses, there is no need for further treatment, medication
is withdrawn and the birds remain well.