Canker (trichomonosis)

Avian trichomonosis, commonly referred to as 'Canker', is an infection caused by the flagellate protozoan, Trichomonas gallinae. One of the main characteristics of the disease is the development of a canker, or caseous plaque in the oral cavity (mouth), esophagus (throat), and crop. The severity of the disease varies depending on the strain of T. gallinae, immune status of the bird, and age. There are numerous strains of T. gallinae, ranging from some which cause no clinical signs to highly pathogenic strains. Younger birds are usually affected more seriously than older, mature chickens.

Columbiforms are the most common host of T. gallinae, with most wild and almost all domestic pigeons and doves being infected. It is estimated that approximately 80-90% of adult pigeons are infected with T. gallinae, many of which develop no clinical signs of disease. Over the past several years, there has been an increasing number of T. gallinae infections reported in chickens, turkeys, and raptors.

Early Clinical Signs

Consist of the appearance of small, hard, well-defined, cream to yellowish sores that are stuck to the side and/or roof of the oral cavity, tongue, edges of the beak, and occasionally covering the glottis. As the disease progresses, these sores increase in size, thickness, and become caseous ('cheese-like') in appearance. Sores are usually found inside the chicken's mouth, but can also develop on the beak exterior and near the eyes. Other non specific clinical signs observed include huddling, listlessness and ruffled feathers from depression. Oral sores that develop inside the mouth are usually easy to see by gently opening the bird's beak and looking inside.

Advanced Stages of Disease

Sores can develop in the chicken's esophagus or throat, where they can potentially block air passage and food which causes the chicken to suffocate or starve to death. When oral sores develop in the chicken's throat, they often impact the chicken's ability to swallow, resulting in reduced feed and water intake and leading to weight loss. Throat sores can also potentially close off the windpipe so that the chicken is unable to breath. In other cases, the disease can progress to a lethal systemic infection, spreading throughout the body. If sores invade the roof of the mouth (oropharyngeal cavity) and sinuses, they can potentially penetrate through the base of the chicken's skull and into the brain.

How Chickens are Infected

Chickens become infected with T. gallinae by drinking or eating from contaminated sources. Water or feed becomes contaminated when infected birds---initially domestic or wild pigeons or doves and later other flock member--drink or eat from the same source as the chickens. T. gallinae can also be transmitted between adult chickens during courtship behavior. T. gallinae can remain infectious for at least 5 days in moist grains and from 20 minutes to several hours in water. Adult chickens that recover from canker may still carry the parasite, but are resistant to reinfection.

Canker Vs Thrush

	Candidiasis (Thrush)	Canker
Body areas affected	Oral cavity, esophagus, and crop	Oral cavity, esophagus, and crop
Pathogen type	Yeast	Protozoan parasite
Pathogen species	Candida albicans	Trichomonas gallinae
Oral lesion appearance	Patches of raised, whitish, dead epithelial debris. The top white pseudomembranes can be wiped off.	Sticky, yellowish-white 'canker-like' masses of caseous, necrotic material.
More likely to occur following	Prolonged antibiotic therapy, concurrent disease, infestation with internal or external parasites, or stressful event.	Pigeons and doves sharing the same water or feed source.
Treatment	Nystatin, copper sulfate	Metronidazole, thyme extract