Synonyms: Cercaria tenax, Tetratrichomonas buccalis, Trichomonas buccalis, Trichomonas elongata.
Hosts: Man, monkeys (Macaca mulatta, Papio sphinx).
Location: Mouth, especially between gums and teeth.
Geographic Distribution: Worldwide.
Prevalence: Common. T. tenax has been found in 4% to 53% of persons examined in different surveys (Wenrich, 1947).
Morphology: The morphology of T. tenax has been studied by Wenrich (1947) and Honigberg and Lee (19 59). The latter remarked on the close morphological resemblance of this species to T. gallinae. The body is ellipsoidal, ovoid or piriform, 4 to 16 u long and 2 to 15 u wide. Different strains differ in size; the smallest of 5 strains studied by Honigberg and Lee (1959) averaged 6.0 by 4.3 u and the largest 8.4 x 6.0 u. The 4 anterior flagella are 7 to 15 u long. They originate in a basal granule complex anterior to the nucleus and terminate in little knobs or rods. The undulating membrane is shorter than the body; it ranged from 40 to 100% and averaged from 69 to 82% of the body length in the 5 strains studied by Honigberg and Lee (1959). An accessory filament is present. There is no free posterior flagellum. The costa is slender and accompanied by a group of large paracostal granules. The parabasal apparatus consists of a typically rod-shaped body and a long filament extending posteriorly from it. The axostyle is slender and extends a considerable distance beyond the body. There is no periaxostylar ring at its point of exit nor is it accompanied by paraxostylar granules. The capitulum of the axostyle is somewhat enlarged and spatulate. The pelta is of medium width. Wenrich (1947) said that a cytostome was present, but Honigberg and Lee (1959) found no evidence of one. Honigberg and Lee (1959) described the division process in detail.
Cultivation: Honigberg and Lee (1959) cultivated T. tenax in Balamuth’s yolk infusion medium. Diamond (1960) cultivated it axenically in a complex medium containing chick embryo extract.
Remarks: Hinshaw (1928) infected a dog which had gingivitis with T. tenax.