Synonyms: Cercomonas gallinae, Cercomonas hepaticum, Trichomonas cohimbae, Trichomonas diversa, Trichomonas halli.
Disease: Avian trichomonosis, upper digestive tract trichomonosis.
Hosts: The domestic pigeon is the primary host of T. gallinae, but it also occurs in a large number of other birds, including hawks and falcons which feed on pigeons. Its natural hosts besides the pigeon include the mourning dove (Zenaidura macroura), Indian dove (Turtur suratensis), wood pigeon (Columba palumbus), band-tailed pigeon (C. fasciata), ring dove (Streptopelia risoria), whitewinged dove (Zenaida asiatica), turkey, chicken, Cooper's hawk (Accipiter cooperi), golden eagle (Aquila chrysaetos), duck hawk (Falco peregrinus anatum), Java sparrow (Munia oryzivora), zebra finch and orange-cheeked waxbill.
A number of other birds have been experimentally infected. They include the bobwhite quail, canary, English sparrow (Levine, Boley and Hester, 1941), barn swallow, goldfinch and song sparrow (Stabler, 1953), and Tovi parakeet and Verraux's dove (Callender and Simmons, 1937). Parenteral infections have also been produced experimentally in mammals - by Bos (1934) in mice and guinea pigs, by Wagner and Hees (1935), Wittfogel (1935), Miessner and Hansen (1936), Schnitzer, Kelly and Leiwant (1950) and Honigberg (1959) in mice, and by Rakoff (1934) in rats and kittens.
Prevalence: T. gallinae is extremely common in domestic pigeons, in which it often causes serious losses. It is fairly common in the turkey; the U.S. Dept, of Agriculture (1954) estimated that it causes an annual loss of $47,000 in these birds. It is rare in chickens. It is common in mourning doves, and may cause serious losses among them (Stabler and Herman, 1951). According to Stabler (1954), it was common in trained hawks during the heyday of falconry; they became infected because they were fed largely on pigeons. Stabler and Herman (1951) and Stabler (1954) give further information on incidence in domestic and wild birds.
Morphology: The following description is based on Stabler (1941, 1954). The body is roughly piriform, 6 to 19 by 2 to 9 u. Four anterior flagella 8 to 13 u, long arise from the blepharoplast. The axostyle is narrow and protrudes a short distance from the body. There is no chromatic ring around its point of emergence. The parabasal body is sausage-shaped, about 4 u, long, with a parabasal filament. The costa runs 2/3 to 3/4 of the body length. The undulating membrane does not reach the posterior end of the body. An accessory filament is present. A free trailing flagellum is absent. A cytostome is present. There are 6 chromosomes.
Pathogenesis: In the pigeon, trichomonosis is essentially a disease of young birds; 80 to 90% of the adults are infected but show no signs of disease. The severity of the disease varies from a mild condition to a rapidly fatal one with death 4 to 18 days after infection. This is due in part to differences in virulence of different strains of the trichomonad (Stabler, 1948). Severely affected birds lose weight, stand huddled with ruffled feathers, and may fall over when forced to move. A greenish fluid containing large numbers of trichomonads may be found in the mouth.
Lesions are found in the mouth, sinuses, orbital region, pharynx, esophagus, crop and even the proventriculus. They do not involve the digestive tract beyond the proventriculus. They often occur in the liver and to a lesser extent in other organs, including the lungs, air sacs, heart, pancreas, and more rarely the spleen, kidneys, trachea, bone marrow, navel region, etc.
The early lesions in the mouth are small, yellowish, circumscribed areas in the mucosa. They increase in number and become progressively larger, finally developing into very large, caseous masses which may invade the roof of the mouth and sinuses and may even extend thru the base of the skull to the brain. The early lesions in the pharynx, esophagus and crop are small, whitish to yellowish caseous nodules which also grow. They may remain circumscribed and separate, or they may form thick, caseous, necrotic masses which may occlude the lumen. The circumscribed, disc-shaped lesions are often described as "yellow buttons". Those in the esophagus and crop may have central, spur-like projections. A large amount of fluid may accumulate in the crop. The lesions in the liver, lungs and other organs are solid, yellowish, caseous nodules ranging up to a centimeter or more in diameter.
In the turkey and chicken, the lesions occur mostly in the crop, esophagus and pharynx, and are relatively uncommon in the mouth and liver. The lesions in the mourning dove are similar to those in the pigeon.
Immunology: As mentioned above, different strains of T. gallinae differ greatly in virulence (Stabler, 1948; Florent, 1938; Gloor, 1943). Previous infection bestows more or less immunity; adult pigeons which have survived infection as squabs are symptomless carriers. Infection with a relatively harmless strain produces immunity against virulent strains (Stabler, 1948a, 1951). According to Florent (1938), pigeons are particularly susceptible at the time of weaning and of the first molt. Stabler (1953) found that immunity did not increase with age of uninfected birds. Certain breeds or strains of birds may be more sensitive than others. Miessner and Hansen (1936) felt that roller and tumbler pigeons were such, and Levine and Brandly (1940) were able to infect chicks from one source readily while chicks from other sources were very resistant.
Epidemiology: In pigeons and mourning doves, trichomonosis is transmitted from the adults to the squabs in the pigeon milk which is produced in the crop. The squabs are infected within minutes after hatching. Hawks and other wild raptors become infected by eating infected birds. Turkeys and chickens are infected thru contaminated drinking water. Feral pigeons and other columbid birds are the original source of infection. The trichomonads pass into the water from the mouths of infected birds, and not from the droppings (Stabler, 1954). T. gallinae has no cysts and is very sensitive to drying, so direct contamination is necessary.
Diagnosis: Upper digestive tract trichomonosis is readily diagnosed by observation of the lesions together with demonstration of the protozoa. It must be differentiated from other conditions which may cause more or less similar lesions, including fowl pox, vitamin A deficiency and moniliosis (thrush).
Cultivation: T. gallinae can be cultivated readily in any of the customary trichomonad media. Diamond (1954) compared 28 culture media for it and (1957) introduced a trypticase-yeast extract-maltose-cysteine-serum medium for it and other trichomonads.
Treatment: A number of workers have recommended the use of copper sulfate for 20 days or more in the drinking water to eliminate T. gallinae (see Stabler, 1954) but this is not particularly satisfactory. The optimal concentration for non-breeding pigeons is 1-1000 and that for breeding pigeons with squabs is 1-3000 according to Jaquette (1948), but it tends to make the birds sick, and Jaquette felt that all the treated birds may have suffered liver damage. Turkeys will not drink 1-2000 copper sulfate.
The best treatment for T. gallinae is 2-amino-5-nitrothiazole (enheptin). Stabler and Mellentin (1953) recommended 7 daily doses of 28 mg/kg for homing pigeons and 45 mg/kg for commercial birds. This treatment cures both acute cases and carriers. Stabler, Schmittner and Harman (1958) used 6.3 g enheptin soluble per gallon of drinking water for 7 to 14 days in non-breeding pigeons. The birds consumed 9 to 27 mg of the drug per day - operation of the peck order may have cut down water consumption by some birds - and 53 of 61 infected birds were freed of their infections. Zwart (1959) obtained promising results with 0.125% enheptin in the drinking water of a Dutch aviary where the infection had been found in zebra finches and an orange-checked waxbilh
Control: Control of trichomonosis in pigeons depends upon elimination of the infection from the adults by drug treatment. Prevention in turkeys and chickens is based upon preventing wild pigeons and doves from drinking from their watering places.