Because infected bulls typically show no outward clinical signs of disease and pathogens other than T. foetus can also infect a cow herd and cause clinical signs of early embryonic death and repeat breeding (infertility), a definitive diagnosis requires isolation of this obligate pathogen from infected animals, particularly bulls. In areas where trichomoniasis is prevalent, annual testing of all herd bulls for this disease agent as part of a breeding soundness exam should be performed 60–75 days prior to turn-out with cows and heifers. This will allow early identification of disease concerns in the event the bulls were exposed to an infected cow or heifer during the last breeding season. If commingling with cattle of unknown trichomoniasis status occurs between the time of bull testing and turn-out (i.e., if a fence was breached), re-testing of the bull(s) should be considered. Preputial smegma is the specimen of choice to use from bulls to identify T. foetus microscopically. This sample is collected by using a plastic artificial insemination pipette to vigorously scrape the surface epithelium in the preputial fornix while simultaneously gently aspirating the dislodged cellular debris and secretions.
Trichomoniasis is a disease of the reproductive tract of both beef and dairy cattle. The causative agent is a protozoan organism (Tritrichomonas foetus) which is typically transmitted venereally under natural breeding conditions when an infected bull breeds an uninfected cow or heifer or when an uninfected bull subsequently breeds a previously infected female. Because most beef producers in the U.S. use natural breeding as their preferred management practice to produce their annual calf crop, most cases of trichomoniasis are diagnosed in beef herds. Fewer cases are seen in dairy cattle because the U.S. dairy industry uses artificial insemination as a management practice to impregnate females.
The economic loss to the cattle producer is a reduced calf crop or lower overall weaning weights. For example, in infected herds with a short defined breeding season, the calf crop can be decreased by 50 percent. In herds with longer breeding seasons such as six months (180 days) or longer, the calving period can be extended. Thus, weaning weights can be dramatically decreased. In smaller, less intensively managed herds, where the problem is not recognized early in the disease process, cows may produce a calf every 18 months, instead of the normal 12 months. This results in both lower weaning weights and fewer calves produced during the life of the cows in the herd.
Bulls harbor this pathogen on the surface epithelium of the penis and preputial membrane and can remain infected indefinitely (remain a carrier). Once introduced into the reproductive tract of susceptible females at the time of breeding, T. foetus has a predilection for colonizing and, then causing inflammation of, vaginal and uterine mucosa. As a result, if conception occurs, pregnant females typically experience early embryonic death and subsequent repeat breeding (infertility). This picture of infertility maintains itself in most infected females for approximately 3 months, a time frame that coincides with their mounting an effective immune response to eliminate infection. Fetal death and abortions can also occur but are not as common as losses earlier in gestation. Tritrichomonas foetus has been found in vaginal cultures taken as late as 8 months of gestation and, apparently, live calves can be born to infected dams. Other reproductive abnormalities such as pyometra, endometritis, or a mummified fetus can occasionally develop in infected females after breeding.
Treatment of infected animals with anti-protozoal drugs has proven ineffective. Consequently, producers have relied on implementing several management practices to control this disease. Most important of these practices is to eliminate the infection from the bull battery by culling all bulls and replacing them with virgin bulls or, alternatively, by testing the bull battery and culling all positive bulls. Reinfection is prevented by exposing only uninfected bulls to uninfected females. Uninfected females are assumed to be those with calves at side (even though some infected cows may produce a live calf) and virgin heifers. A vaccine has also been developed to assist with the control of this disease. However, under field conditions and in the absence of other control measures, vaccination of susceptible cattle has not proven to be highly effective in mitigating disease transmission.
Currently, there are no Federal regulations specific to curbing spread of trichomoniasis in the U.S. cattle population. However, a growing number of states have independently adopted trichomoniasis control and management regulations regarding the interstate movement of cattle to limit disease spread. Although the goal of these regulations remains the same between the States adopting them, requirements remain inconsistent among individual States. USDA recommends veterinarians contact the State animal health official of the destination State for specific import requirements.