COMPARISON OF DIAGNOSTIC METHODS FOR DETECTION OF ACTIVE INFECTION WITH TRITRICHOMONAS-FETUS IN BEEF HEIFERS

Objective-To compare sensitivity of a generic trypticase-yeast extract -maltose (TYM) medium versus a commercial nutrient medium in the diagn osis of Tritrichomonas foetus infection in heifers and to assess sensi tivity when incubation of samples inoculated into commercial medium po uches is delayed overnight. Design-Prospective study. Animals-30 virgi n beef heifers. Procedures-20 heifers vaccinated with a trichomonad an tigen and 10 unvaccinated control heifers were exposed at synchronized estrus by intravaginal instillation of 10(6) T foetus organisms. Cerv icovaginal mucus samples were collected every other week for 10 weeks from controls and once (10 weeks after exposure) from vaccinated heife rs. Samples were inoculated into both media and immediately incubated at 37 C (98.6 F). A duplicate inoculation from controls was made into commercial medium, and the pouch was shipped overnight to a diagnostic laboratory without prior incubation. Results-For 40 of 50 samples fro m control heifers, there was agreement on diagnoses between media. The re was agreement on a positive diagnosis for 3 of 20 samples from vacc inated heifers and on a negative diagnosis for 15 of these 20 samples. For samples shipped overnight before incubation, there were 10% fewer positive diagnoses, compared with samples incubated immediately in co mmercial medium and 10% more positive diagnoses, compared with samples immediately incubated in TYM. Clinical implications-Use of the commer cial medium is a more sensitive indicator of current infection in heif ers than use of generic TYM medium. In herds where infection prevalenc e is high, this method is likely to identify more infected females, an important consideration when control programs include culling of infe cted cows.