PERSISTENCE OF TRITRICHOMONAS-FETUS IN NATURALLY INFECTED COWS AND HEIFERS IN ARGENTINA

Tritrichomonas foetus infection was investigated in 76 pregnant and 64 non-pregnant cows slaughtered in the local abbattoir and in two diffe rent lots of first-service heifers that were found to be non-pregnant 60 days post breeding (PB). In live and slaughtered animals, mucus sam ples were obtained from the vagina and from the vagina and uterus, res pectively, using a ''screw-head scraper rod''. In pregnant cows, sampl es of amniotic and allantoid fluid were also collected, as well as sam ples from the stomach contents of the fetuses. All samples were cultur ed in Modified Plastridge Medium. T. foetus was isolated from three pr egnant and two non-pregnant slaughtered cows. Parasites were recovered from the vagina of these five cows, as well as from the uterus in two cases and from the fetus in one case. Lot I of first-service heifers consisted of 323 females from eight different farms. Bulls infected wi th T. foetus from these farms were culled or treated, and heifers foun d empty at diagnosis of pregnancy were culled. Lot II consisted of 120 heifers from a single farm where T.foetus was controlled only in bull s. All heifers from Lot I were T. foetus negative. In Lot II, 12 of 12 0 heifers (10%) were T. foetus positive. In ten of these the parasites were observed once, in one at 60 days PB, in seven at 160 days PB and in two at 240 days PB; in the remaining two infected heifers, an irre gular pattern of isolation persisted during 300 days PB. On the basis of these results, control methods are discussed and analysed.