INFECTIONS IN PIGEONS
By Dr Colin Walker BSc, BVSc, MRCVS,
MACVSc (Avian health)
Streptococcus is the name given to
a group of dot-shaped bacteria that are capable of causing disease
in pigeons. They are everywhere in the environment, mainly in the
dust and air. Many species have been isolated from pigeons and
they are considered part of the normal bacteria found on the skin
and the lining of the digestive, respiratory and reproductive tracts.
There are different types of Streptococcus that vary in their ability
to cause disease. Transition from a normal bacterial inhabitant
to a disease agent depends on how effectively the pigeons’ immune
system is operating.
Experimentally, researchers have deliberately infected pigeon
s with disease-causing strains of Streptococci, both by intravenous
injection and by mouth. Many of those infected by the intravenous
route became sick, developing a variety of symptoms. Interestingly
however, in the pigeons inoculated with the organism by mouth,
none became sick, although the organism could be cultured from
the droppings or mouth of at least half of the pigeons in the
month following infection. This experiment helps to explain
the nature of the disease process with Streptococcus. Pigeons
are obviously being exposed to the organism intermittently
but when an otherwise healthy pigeon ingests the organism,
disease is unlikely to occur. Once the organism, however, gains
entry to the blood stream, the pigeon can become unwell. In
some studies, potentially harmful species of streptococci have
been recovered from the intestines from up to 40% of healthy
pigeon s. Many pigeon s obviously carry these organisms without
becoming sick. As with other diseases in pigeons, there needs
to be a trigger factor that enables the organism to invade
the blood stream and spread throughout the body. This trigger
is essentially any factor that runs the pigeon down. Predisposing
factors include poor management, poor loft environment and
concurrent disease, but also the ability of the type of Streptococcus
itself to cause disease.
Signs associated with disease
Once the bacteria have invaded the body of a vulnerable bird,
it can spread to a variety of sites. This, together with
the fact that the severity of the disease can vary, leads
to a wide variety of symptoms that often mimic other diseases.
It is therefore important that pigeon fanciers do not jump
to a premature conclusion that this is the problem with any
unwell pigeons they may have.
Once the organism invades from the bowel or skin, etc, into
the blood stream, it can be carried to a wide variety of sites.
The symptoms displayed by the pigeons depend on the actual
site within the body that the bacteria infect and also the
severity of the infection. Disease displayed by the pigeons
can be per acute or chronic. Some pigeons develop a severe
overwhelming disease and will die so quickly that they do not
have time to lose condition. These pigeons become quiet, fluffed
up and die within 2 – 3 days. Other pigeons, develop
a chronic ill-thrift type condition that may persist for as
long as 6 – 8 weeks. Some of these pigeons with treatment
will recover, while others will eventually die. In some apparently
recovered pigeons, relapses can occur. In still other pigeons,
the disease may be transient and mild.
In some infected pigeons, the organism will localise in the
respiratory system, leading to red watery eyes, a nasal discharge
and difficulty breathing. In other pigeons, the liver can be
affected, leading to a green diarrhoea and weight loss. In
some pigeons, the heart itself may become infected. If these
pigeons survive, they may develop long-term heart problems,
leading to a chronic shortage of breath. The organism can also
infect the membrane around the brain (leading to poor coordination,
loss of balance, or a head tilt), the muscles (leading to bleeding
and inflammation), the joints (leading to swollen red painful
joints, in particular in the wings and legs), the kidney (leading
to a thirst and excessive urination), the bowel (leading to
diarrhoea), the abdomen (leading to fluid accumulation and
a swollen abdomen) and testicles (leading to premature infertility
in young cocks). Notably, the organism can also infect the
ovary and fallopian tube of hens. This can lead to interference
with ovulation, meaning that some hens will become sterile
or lay eggs late or irregularly. In those that do lay, the
organism can be incorporated in the egg at the time of its
formation, leading to embryonic death during incubation or
a weakened chick that dies during hatching or shortly after.
Because the organism is found in pigeons droppings, it can
contaminate the nest box and infect the healing navel of recent
Because of the wide variety of symptoms associated with the
disease, the disease cannot be diagnosed by the signs displayed
by the pigeons. Similarly, the disease cannot be diagnosed
through examination of the droppings as it is found there
normally in many pigeon s and most of these will be quite
healthy. The only way to diagnose the disease is by culturing
the organism from certain organs during autopsy. Swabs for
culture are usually taken from the heart, brain, liver or
a visible lesion.
Treatment and control
As always, good ongoing care will mean that most pigeons are
able to resist the disease and those that do get sick are in
the best situation to recover. When Streptococcal disease is
diagnosed, it is vital for the pigeon fancier to identify and
correct the flaw in his management or loft environment that
has enabled the disease to flare up in the first place. Otherwise,
a poor response to any medication can be anticipated.
Being a bacterial infection, the organism responds to antibiotic
treatment. And so, what are the best antibiotics to use? The
best way to treat is to have your veterinarian culture the
Streptococcal organism involved in your outbreak and also have
him do what is called a sensitivity test in order to ascertain
what is the most effective antibiotic for that particular strain
of Streptococcus. Studies do, however, show that 80% of organisms
are controlled by the antibiotics ampicillin (a synthetic penicillin)
and doxycycline, while 70% are sensitive to erythromycin, 30%
are sensitive to enrofloxacin (Baytril) and only 10% are sensitive
to sulfur-based antibiotics. Obviously, the two poorest drugs
are Baytril and the sulfur-based antibiotics, so they are not
likely to be the first choice for treatment of this disease
(although obviously they are useful in other situations). In
the absence of testing, doxycycline is the usual choice as
it is equally effective as the synthetic penicillins but is
As with other bacterial bowel diseases, probiotics have a
significant role to play in the control of Streptococcal infections.
They can be used in times of stress when the normal bowel bacteria
are disrupted to minimise the risk of Streptococcal invasion
and also to preventatively treat healthy pigeons that have
been in contact with pigeons infected with Streptococcus. Interestingly,
exhibitors of fancy breeds have noticed how Streptococcal diarrhoea
can be avoided in pigeons taken to shows if the pigeons are
treated with probiotics, eg Probac, for several days before
and after the show.
Maintenance of a clean, dry loft will minimise exposure to
the organism. If necessary the loft can be disinfected. Streptococci
are sensitive to most of the commonly used disinfectants.
When Streptococcal infection occurs in an loft, it will spread
slowly through the flock and some pigeons will start to die.
When testing by your veterinarian confirms the disease, the
following protocol can be followed:-
Unwell pigeons are separated and either treated with doxycycline
tablets, eg Vibravet 50 mg, ½ tablet once daily, or
Loft cleaned and disinfected.
Trigger factors such as overcrowding, poor diet, low hygiene,
inadequate parasite control, cold or damp conditions etc etc,
are identified and corrected.
Start in-contact healthy pigeons on probiotics.
If further pigeons continue to become unwell while on the probiotic
treatment, then start a flock treatment of antibiotic eg. Doxycycline, “Doxyvet”.