Persistence of Tritrichomonas foetus 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 different lots of first-service heifers that were found to be non-pregnant 60 days post breeding (PB). In live and slaughtered animals, mucus samples were obtained from the vagina and from the vagina and uterus, respectively, using a "screw-head scraper rod". In pregnant cows, samples of amniotic and allantoid fluid were also collected, as well as samples from the stomach contents of the fetuses. All samples were cultured in Modified Plastridge Medium. T. foetus was isolated from three pregnant 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 with T. foetus from these farms were culled or treated, and heifers found empty at diagnosis of pregnancy were culled. Lot II consisted of 120 heifers from a single farm where T. foetus was controlled only in bulls. All heifers from Lot I were T. foetus negative. In Lot II, 12 of 120 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 irregular pattern of isolation persisted during 300 days PB. On the basis of these results, control methods are discussed and analysed.