Trichomoniasis is a contagious venereal disease of cattle caused by the flagellated protozoan organism Tritrichomonas foetus which can lead to infertility through early embryonic death and abortion.
Disease due to T. foetus is particularly prevalent in large beef herds managed under extensive conditions where mating is uncontrolled (e.g. across northern Australia). Disease is transmitted when infected bulls mate with susceptible cows and vice versa. Bulls if infected at less than 3 years of age may clear the infection but those infected at 3 years and older are usually infected for life. Most cows are free of infection within 3-4 months after breeding, but immunity is not long lasting and reinfection can occur if again mated to infected bulls.
The best indication of Tritrichomonas infection is seen when females keep returning to the bull, four to five months after being initially served. Often, the incidence for this is higher in heifers rather than in mature cows.
Extended calving intervals with more cows calving late in the season, low calving rates, and low branding and weaning rates, are typical signs.
Infection can cause early embryonic death shortly after conception, or if the affected embryo survives longer, abortions may occur but usually before 5 months. A persistent vaginal discharge often occurs in affected cows but under extensive management conditions it is unlikely to be seen. Bulls show no obvious symptoms of infection but may be seen to be ‘lazy’ at service.
The disease is transmitted by sexual contact. Bulls are a reservoir of infection and any animal of breeding age is susceptible. The organism lives in the uterus of the cow where it produces inflammation which either prevents conception or causes an early abortion. In bulls, the organism lives on the penis and in the surrounding prepuce. Transmission is also possible if semen from infected bulls is not collected appropriately and used for artificial insemination.
Diagnosis is made on a microscopic examination of vaginal discharge from cows or preputial scrapings from bulls, but this technique may not detect all infected animals. Definitive diagnosis requires culture and identification of the organism from an affected animal in the herd. Testing for both Tritrichomonas and other reproductive diseases such as vibriosis is usually done on the same samples.
Figure 1. TRICAMPERTM sampling tool for collecting samples of vaginal discharge from cows, or preputial scrapings from bulls, to test for Tritrichomonas foetus. Image courtesy of Queensland Department of Agriculture and Fisheries.
Figure 2. Stained Tritrichomonas foetus trophozoites with undulating membranes. Image courtesy of Josef Reischig Wikimedia Commons
Vaccines have not been highly effective, especially in the absence of other control measures. Infected bulls should be culled and only young bulls mated with heifers. Short interval mating of 3-6 months will provide sexual rest for cows and enable better disease control through the development of immunity.