Synonym: Trichomonas pullorum.
Hosts: Chicken, turkey, guinea fowl, and possibly other gallinaceous birds such as the quail, pheasant and chukar partridge. Diamond (1957) found a T. gallinarum-like form in the Canada goose (Branta canadensis).
Location: Ceca, sometimes liver.
Geographic Distribution: Worldwide.
Prevalence: Common. McDowell (1953) found T. gallinarum in over 60% of a large number of chickens in Pennsylvania.
Morphology: The body is piriform, 7 to 15 by 3 to 9 u, with 4 anterior flagella and a posterior flagellum which runs along the undulating membrane and extends beyond it. An accessory filament is present. The axostyle is long, pointed and slender, without a chromatic ring at its point of emergence. The cytostome is prominent. Supracostal granules but no subcostal or endoaxostylar granules are present. The pelta is elaborate, ending abruptly with a short ventral extension more or less free from the ventral edge of the axostyle, according to McDowell (1953); Marquardt (1954), however, did not find a pelta in his cultures of a strain from a turkey. The shape of the parabasal body is highly variable, but it is usually a ring of variously spaced granules plus 1 or 2 fibrils or rami. The chromosome number is apparently 5. A rather uniform perinuclear cloud of argentophilic granules is usually present (McDowell, 1953).
The form originally described by Martin and Robertson (1911) had 4 anterior flagella. Allen (1940) described a trichomonad from the ceca and liver of chickens and turkeys which she considered to be this species but which had 5 anterior flagella. Walker (1948), too, illustrated the trichomonad he isolated from turkey livers with 5 anterior flagella. Further study is needed to determine the relationship of this form to T. gallinarum. McDowell (1953) insisted on the fact that the usual number of anterior flagella is 4, rarely 3 and in even rarer cases 5. He studied 1000 slides from a large number of chickens. Marquardt (1954), too, found only 4 anterior flagella in a culture strain from a turkey.
Pathogenesis: Allen (1936, 1941), Olsen and Allen (1942) and Walker (1948) isolated a trichomonad from turkey liver lesions resembling those of histomonosis and considered that the trichomonad had caused them. The disease they described resembled histomonosis, with cecal and liver lesions, pale yellow, cecal diarrhea, inappetance, loss of weight, and a mortality of 0 to 44%. The cecal lesions were said to be the same as those of histomonosis, but the liver lesions were said to be smaller, to have irregular outlines and to be raised or level with the liver surface instead of depressed below it. Wichmann and Bankowski (1956) described a similar condition in chukar partridges. However, the mere presence of an organism in a lesion is no proof that it caused the lesion. There is no satisfactory proof that T. gallinarum by itself is capable of causing disease, and the weight of evidence is against it. Delappe (1957) infected chickens and turkeys experimentally with a strain of T. gallinarum isolated from liver lesions of a turkey with histomonosis, but was unable to produce either symptoms or lesions. The possibility has still not been completely eliminated, however, that a Pentatrichomonas may exist which is pathogenic (see below).
Epidemiology: Birds become infected by ingestion of trichomonads in contaminated water or feed. McLoughlin (1957) found that one-week-old turkey poults were more susceptible than 9-week-old ones. He also found that T. gallinarum survived for 24 hours but not for 48 hours in cecal droppings at 37° C, and for 120 hours at 6° C.
Cultivation: T. gallinarum is readily cultivated in the usual trichomonad media.