Trichomoniasis and other STDs in beef cattle (Proceedings)
Trichomoniasis is a sexually transmitted reproductive disease of cattle caused by Tritrichomonas foetus (formally named Trichomonas foetus). There has been a re-emergence of the disease due to increased movement of breeding cattle across the country. The disease is characterized by infertility and early embryonic death. However, most producers do not recognize a problem until cattle are checked for pregnancy. Affected herds may see 40-60% late and open cows. Bulls are asymptomatic carriers of the protozoa that infect the cow during breeding. Infected cows will experience fetal loss and then clear the infection and be able to sustain a pregnancy.
The T. foetus protozoa can live in the cow's reproductive track and the surface of bull's penis. In bulls the protozoa will embed into penile crypts and most infected bulls will become permanent carriers. The bull spreads the disease by mechanical vector during breeding. There are not any treatments for this disease and carrier bulls should be culled for slaughter. There have been some reported instances when young bulls were able to clear the infection. However, as a bull ages the penile crypts become deeper allowing the protozoa to permanently establish itself. Up to 90% of cows will become infected when bred by a carrier bull. Cows will eventually develop a temporary immunity to the organism and maintain a pregnancy. If there is an extended breeding season these cows will be late bred. However, with shorter breeding seasons the cow will not have time to develop immunity and will not be pregnant.
The progression of the disease within a herd is variable depending upon source of the infection and duration of breeding season. Often times the disease is not diagnosed the first year it infects the herd. If an infected open female is added to the herd there would be very little change in reproductive performance. A small percentage of cows may have been infected and became late bred animals. However, one or more bulls likely became infected carriers and will infect all the cows they breed the next year. Subsequently, more bulls will become infected that breeding season. In the third year multiple bulls will be infected and up to half the cows will be open or late bred. If the disease is allowed to persist in the herd pregnancy rates will recover in subsequent years but reproductive performance will never be optimal. Some practitioners report an increased incidence of pyometras in beef cows.