Trichomas infection in a bull--an apparent change in serotype of the infecting organism.

Routine serotyping of T. foetus isolates from a bull and infected cows showed that the strain in the bull had apparently changed from var. brisbane to var. belfast over a period of 4 months between tests. The significance of this change in the predominance of one serotype over another in mixed infections in vitro and in herds was discussed. The report indicates that the phenomenon should be considered in studies on the epidemiology of trichomoniasis.