Trichomoniasis

This fact sheet was updated on 1/27/21.

Other names: Canker, Frounce, Avian trichomoniasis

Cause

Trichomoniasis is an infectious disease of birds caused by the single-celled protozoan Trichomonas gallinae and Trichomonas stableri. The parasite inhabits the upper digestive tract, mainly the crop and esophagus. While some strains of the protozoa do not cause disease, others can result in death. In pigeons and doves this disease is also known as Canker, in raptors it is known as Frounce. Trichomoniasis is one of the oldest known wildlife diseases with written records dating back to the 1500s. The protozoan responsible for the disease was not isolated until 300 years later.

Significance

Trichomoniasis is considered the most important disease of mourning doves in North America and can result in major mortality events in these species. The largest outbreak of trichomoniasis occurred between 1950-1951 in Alabama and neighboring states resulting in the death of 50,000 to 100,000 mourning doves. Since it is a feeder-associated disease, it may also lead to serious population declines in some species of songbird.

Species Affected

Trichomoniasis is primarily a disease of pigeons and doves, but raptors are also commonly affected. On rare occasions waterfowl and upland game birds have been affected. Domestic turkeys, chickens, and other captive birds can also be infected. T. gallinea and T. stableri are not known to infect humans.

Distribution

Trichomoniasis occurs in birds worldwide except Antarctica, Greenland, and the northern reaches of North America, Europe, and Asia. The protozoa likely occurs wherever rock pigeons and mourning doves are found.

Transmission

Adults birds are the reservoir host for this organism. The protozoa are shed into the environment in the oral secretions of infected birds. Protozoa may directly pass from one adult to another through bill-to-bill contact, which is common during courtship. Young doves and pigeons acquire the protozoa when they receive regurgitated food from infected adults during feeding. Susceptible birds may also consume T. gallinae and T. stableri in contaminated food or water. The protozoa are transmitted to raptors when they feed on infected birds.

T. gallinae and T. stableri are killed by drying but can survive for up to 5 days in moist grain and 20 minutes to several hours in water. Supplemental feeding and other practices that congregate susceptible bird species can lead to local mortality.

Clinical Signs

Clinical trichomoniasis is primarily a disease of young pigeons and doves and is often fatal. 80-90% of adult pigeons carry T. gallinae and/or T. stableri but show no clinical signs of illness. The severity of the disease depends on the susceptibility of the bird and the pathogenicity of the strain of the parasite. Mild infections can produce immunity to more virulent strains.

The protozoa inhabit the upper digestive tract of all affected birds, leading to inflammation of the lining of the mouth and esophagus, which can develop into cheese-like masses. The lesions within the upper digestive tract grow rapidly and coalesce to form masses that frequently interfere with eating and drinking. Birds that are unable to swallow often become emaciated and listless. Affected birds may also exhibit ruffled feathers, be unable to close their mouth, develop ocular discharge, diarrhea, and have difficulty breathing. Their necks and faces often appear puffy or swollen. Birds lose weight rapidly and usually die within 8-10 days from starvation because they cannot swallow or suffocate due to blockage of the trachea.

Diagnosis

A presumptive diagnosis can be made based on the presence of classic lesions on necropsy. Laboratory identification of the organism microscopically, by culture or PCR, is required for a definite diagnosis.

Treatment

Medications are available that can successfully treat trichomoniasis in birds. Captive birds can be treated by oral administration of the medication or by adding the medication to food and water. Treatment is challenging and likely not feasible in wild populations.

Management

Management of trichomoniasis centers around sanitation and biosecurity. Doves and pigeons should be prevented from congregating in large groups, particularly at birdbaths and feeders. Where feeding does take place, both food and water should be kept fresh and changed daily. Feeders, platforms, and other associated surfaces should be decontaminated regularly with a 10% bleach solution (9 parts water: 1 part bleach). Infected captive birds (symptomatic and asymptomatic carriers) should be culled or treated.

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