Information from Cornell Laboratory of Ornithology
Link to this website is included below

Trichomoniasis is a disease that most commonly affects pigeons, doves, and the raptors that feed on them. It is characterized by raised lesions in the mouth, esophagus, and crop. Infected birds may appear to have trouble closing their mouth. The disease is caused by the protozoan Trichomonas gallinae, which is often present in the mouth secretions of birds that appear to be healthy but are carriers of the disease, such as pigeons.

Infected birds can contaminate water containers (bird baths) with their oral secretions, which can, in turn, expose many other birds to the disease. Mortality from this disease varies, but it can be quite high.

According to the Cornell Laboratory of Ornithology, the general consensus is that the disease is often spread through fecal contamination of food or direct contact. The likelihood of consuming contaminated food or coming into direct contact with infected birds is increased near concentrated food sources. Feeders are the ultimate in concentrated food sources. So, Cornell Laboratory of Ornithology believes that it is always a good idea to keep feeders and feeding areas clean in order to promote a safe feeding environment.








Cause:
Avian trichomoniasis is caused by a single celled protozoan, Trichomonas gallinae. Avirulent T. gallinae strains that do not cause disease and highly virulent strains are both found in nature and circulate within bird populations. The factors that make a strain virulent are not known, but they are thought to be controlled genetically within the parasite. Similarly, the reasons why an avirulent or a virulent form of the parasite is found within a bird population at any period of time also remain unknown. Virulent strains of T. gallinae have caused major mortality events or epizootics in doves and pigeons in addition to less visible, chronic losses. Infection typically involves the upper digestive tract of doves and pigeons, but other species have also been infected. Trichomoniasis in doves and pigeons, but not in other species, is generally confined to young birds. The parasite was introduced to the U.S. with the introduction of pigeons and doves brought by European settlers. It has been reported that 80 to 90 percent of adult pigeons are infected, but they show no clinical signs of disease. It is speculated that most of these birds became immune as a result of exposure to avirulent strains of the parasite or because they survived mild infections. In pigeons and mourning doves, the parasites are transmitted from the adults to the squabs in the pigeon milk produced in the crop of the adult. Squabs usually become infected with the first feeding of pigeon milk.

Species Affected
Trichomoniasis is considered by many avian disease specialists to be the most important disease of mourning doves in North America. Band-tailed pigeons have also suffered large-scale losses from trichomoniasis. This disease has been reported as a cause of mortality in birds of prey for hundreds of years prior to the causative organism being identified. Songbirds are less commonly reported to be infected, but T. gallinae is reported to be the most important trichomonad of caged birds; it is often responsible for epizootics among captive collections. Domestic turkeys and chickens also become infected.

Websites for More Information

http://www.birds.cornell.edu/pfw/AboutBirdsandFeeding/DiseasedBirds.htm
Cornell Laboratory of Ornithology's information. This site includes information on other diseases in addition to Trichomoniasis.

http://www.nwhc.usgs.gov/pub_metadata/field_manual/chapter_25.pdf
Information from the National Wildlife Health Center. This site includes graphs that may help explain the incidence of trichomoniasis in songbirds.

http://www.michigan.gov/dnr/1%2C1607%2C7-153-10370_12150_12220-27288--%2C00.html
Information from the Michigan Department of Natural Resources. Includes information on transmission of the disease, pathology, diagnosis, control, and significance.

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex4444/$file/663-34.pdf?OpenElement
Information from Alberta's Agri-Facts. This file is in a pdf format which can be printed.