Preliminary characterization of a Tritrichomonas foetus-like protozoan isolated from preputial smegma of virgin bulls

Abstract

Trichomonad isolates from 14 virgin beef bulls in 3 California herds were submitted to the California Veterinary Diagnostic Laboratory for confirmation of a diagnosis of bovine trichomoniasis. Specimens were submitted in self-contained diagnostic pouches and produced cultures with a protozoan like Tritrichomonas foetus. Under bright-field microscopy, large numbers of single-celled motile organisms, approximately 12 μm x 9 μm, with multiple anterior flagellae, a posterior flagellum, axostyle, and a clearly visible undulating membrane were detected. Motility was jerky and rolling. Air-dried smears of cultures stained with Giemsa or Diff-Quick/iodine revealed an organism similar to T. foetus, although somewhat more rounded (less spindle-shaped). Several organisms appeared to have 4 flagellae, and there were numerous dark-staining bodies in the cytoplasm. Scanning electron micrographs (5000 X) clearly showed four anterior flagellae and an undulating membrane on most organisms, and an axostyle that was consistently longer than that seen in T. foetus. Specific primers for T. foetus were used in a polymerase chain reaction (PCR) assay. No amplification product was detected from any of the "virgin bull" isolates, while positive control isolates of T. foetus all yielded an amplicon of the expected size. On the basis of this partial morphological and molecular characterization, it was tentatively concluded that the isolated organism is not T. foetus, and speculate that it may be a commensal organism of the lower bowel. The recovery of non T. foetus trichomonads in a commercially available diagnostic system suggests that more specific methods may be needed for discrimination among trichomonads isolated from the preputial cavity of bulls.