15.8% (9/57 herds) of California cow-calf herds were affected with trichomonosis in a 1990 study (BonDurant RH, et al; Prevalence of trichomoniasis among California beef herds; J Am Vet Med Assoc 1990; 196(10): 1590-1593). This study tested 729 bulls from 57 herds. Herd size, as judged by number of bulls, ranged from 1 to 210 bulls (median = 6 bulls per herd).

CDFA expects to garner a better understanding of current trichomonosis prevalence in California in the coming years thanks to updated regulations requiring all positive and negative trichomonosis tests be reported.

True economic costs of trichomonosis are difficult to quantify. One study out of UC Davis estimated that combinations of risk factors contributed to a loss of income up to 22% (Villarroel A, Carpenter TE, BonDurant RH; Development of a simulation model to evaluate the effect of vaccination against Tritrichomonas foetus on reproductive efficiency in beef herds; Am J Vet Res 2004; 65(6): 770–775). This study found shared grazing to be the most significant risk factor for a decrease in calving incidence attributable to T. foetus infection. Additional risk factors included bulls not being tested negative for T. foetus prior to breeding and herds containing a higher proportion of older bulls (bulls »3 years of age).

Another disease model predicted, “a reduction of 14 to 50% in annual calf crop, a prolonged breeding season, a reduction of 5 to 12% in the suckling / growing period, a reduction of 4 to 10% in pounds of marketable calf crop at weaning, a reduction of 4 to 10% in monetary return per calf born, and a substantial reduction of 5 to 35% in the return per cow confined with a fertile bull.” (Rae DO. Impact of trichomoniasis on the cow–calf producer's profitability. J Am Vet Med Assoc 1989; 194 (6): 771–775).

Losses to cow–calf herds include cost of replacement bulls, loss of genetic potential due to culling, increased days–to–conception, and subsequently lighter weaning weights.

Tritrichomonas foetus infections have not been documented in humans, nor are there any known risks to humans for contracting this disease from cattle. T. foetus is a venereal disease of cattle; it has not been documented as a cause of venereal disease in other species. This protozoa has not been found to cross mucosal barriers from genital organs into the blood or meat of infected animals.

However, trichomonads have been discovered in other species. A trichomonad closely related to T. foetus was identified in a bronchoalveolar lavage sample from a patient with AIDS in association with Pneumocystis pneumonia. Additionally, there is a single report of a man being treated with subarachnoid (space around brain) anti-cancer drugs that were somehow contaminated with T. foetus; this patient subsequently died of protozoal myelitis. T. foetus has also been identified as a cause of diarrhea in cats. These findings have brought into question previously held beliefs that trichomonads are species specific. Research is active and ongoing to determine how closely trichomonads in different species are related and if any zoonotic potential exists.

Cows are potential sources of new infections and maintaining the organism in a herd. Usually they only harbor the organism for a few heat cycles after infection or pregnancy loss. Some cows can carry the organism through the gestation period and well into the postpartum period. Skirrow found two of 40 infected cows from two herds that carried the infection through the entire gestation and for up to nine weeks postpartum (Skirrow SZ. 1987. Identification of Trichomonad-Carrier Cows. JAVMA. 191:553-554).

Such a 'carrier cow' presents a problem when trying to control the disease and offers at least partial explanation for the persistence of infected animals when control measures have concentrated on eliminating positive bulls. True prevalence of carrier cows is unknown, but is thought to be less than one (1) percent. These cows may be clinically affected (abortion, infertility, pyometra) or there may be no apparent clinical signs.