Trichomoniasis (pigeon canker) is the most
common disease of pigeons. Approximately 80
percent of pigeons are infected with this organism.
The organism is a microscopic flagellate classified as
a protozoan. Different strains, Trichomonas gallinae
or Trichomonas columbae , vary greatly in their
ability to cause disease. The disease occurs
worldwide in warm climates or during warm weather.
It may occur at any time of the year in commercial
squab operations. Adult pigeons frequently carry the
trichomonads without showing signs of disease.
When the adult pigeon is stressed, however, the
organisms may multiply profusely. A mild infection
can then turn into a serious condition. Stresses
include other diseases, parasitic infestations, or
overbreeding.
Affected pigeons in a loft may cease to feed,
become listless and ruffled in appearance, and lose
weight before death. Pigeons often have difficulty
when closing their mouths because of lesions in the
oral cavity. They drool and make repeated
swallowing movements. Watery eyes may be
apparent in birds with lesions located in the sinuses
or tissues around the eyes. Diarrhea, increased water
intake, and respiratory distress may be noted. Birds
may die suddenly due to suffocation if the lesion
blocks the opening of the trachea. The disease
becomes more severe in birds that are noticeably
emaciated. The thin weakened bird loses the
inclination to fly and will "take to the wing"
reluctantly.
Pigeons that are carriers often transmit
trichomonads to their young during feeding. The
disease is common in 10- to 24-day-old squabs. As a
method of feeding their young, pigeons regurgitate
the sloughed, fat laden cells lining the crop (crop
milk) into the oral cavity of the squabs. If squabs are
infected with only small numbers of the protozoan,
they may develop immunity which is maintained by
constant low-level exposure. If squabs are infected
with large numbers, a severe outbreak may occur and
endanger the entire young generation.
Lesions of canker are usually most extensive in
the mouth, pharynx, or esophagus but may occur at
other sites including the crop, proventriculus, or
sinuses. The infection is promoted by minor injuries
to these tissues. The spelts and awns from grains can
easily cause small lesions. The lesions first appear as
small, circumscribed, and elevated areas on the
surface of the oral mucosa. They may be surrounded
by a thin red zone. The lesions may increase in size
Pigeon Canker 2
and coalesce. The build-up of white to yellow/tan
caseous material may be sufficiently extensive to
partially or completely block the lumen of the
esophagus. Organisms may also enter the body
through the unhealed navel of squabs. In this form,
necrotic tumor-like swellings occur under the skin
adjacent to the navel. Lesions can spread to various
internal organs, particularly the liver. Large,
well-defined, and yellowish areas of hepatic necrosis
may be found on necropsy examination.
Typical signs and lesions are very suggestive of
the disease. Demonstration of large numbers of
organisms in the oral fluids is usually considered
enough evidence for diagnosis. The small plaques in
the mucosa should be differentiated from pox,
vitamin-A deficiency, or candidiasis.
Since the organism is transmitted from parent to
squab, every effort should be made to treat or remove
infected birds from the flock. If possible, depopulate
at regular intervals and thoroughly clean and disinfect
the premises.
In addition, the following preventive measures
should help: practice a high standard of sanitation at
all times; do not add birds to an established flock
since they may be carriers (if birds are added,
quarantine for 30 days); and provide a source of
clean, fresh water eliminating all sources of stagnant
water.
The antiprotozoal drugs which were used
successfully in treating this disease, such as
dimetridazole and metronidazole, have been removed
from the market. Experimentally, a number of drugs
are active against trichomonas infection. Use of 0.1%
copper sulfate (100 mg per 100 ml of drinking water),
0.5% hydrochloric acid or 0.02% mercuric chloride
(sublimate) is worth investigating. The optimum
time to treat breeding pairs is at the initiation of egg
production.
