Trichomoniasis in Cows: Infertility, Pregnancy Loss, and Bull Testing
- Trichomoniasis is a sexually transmitted cattle disease caused by the protozoan *Tritrichomonas foetus* and is a major cause of reduced herd fertility.
- Bulls usually show no outward signs, so herd problems are often first noticed as repeat breeding, more open cows at pregnancy check, a longer calving season, or early pregnancy loss.
- Diagnosis usually focuses on testing bulls with preputial samples for PCR or culture, often as part of a breeding soundness exam before turnout.
- There is no reliably effective legal treatment for infected bulls in the U.S.; positive bulls are commonly removed from the breeding herd, while many cows clear infection after several months of sexual rest.
- Prevention centers on biosecurity: use virgin or test-negative bulls, avoid sharing or leasing bulls, maintain a defined breeding season, and work with your vet on herd testing and culling plans.
What Is Trichomoniasis in Cows?
Trichomoniasis, often called trich, is a venereal disease of cattle caused by the protozoan parasite Tritrichomonas foetus. It spreads mainly during natural breeding, although infected semen can also transmit it. The disease does not usually make cattle look sick, but it can have a major effect on reproduction and herd profitability.
In cows and heifers, trichomoniasis is most often linked to early embryonic death, infertility, repeat breeding, and occasional abortion or pyometra. Many females eventually clear the infection if they have enough sexual rest, but that delay can still mean more open cows, later-calving cows, and a less uniform calf crop.
Bulls are the main long-term carriers. The parasite lives in the folds of the prepuce, especially in older bulls, and infected bulls usually have no visible symptoms at all. That is why a herd can have a fertility problem for a full breeding season before anyone realizes trich may be involved.
If your herd has lower-than-expected pregnancy rates or a longer calving season, your vet may recommend looking at trichomoniasis alongside other reproductive causes such as bull infertility, campylobacteriosis, nutrition issues, or timing problems.
Symptoms of Trichomoniasis in Cows
- Repeat breeding or cows returning to heat
- Lower pregnancy rates at herd pregnancy check
- More open cows than expected
- Extended calving season
- Early pregnancy loss
- Occasional abortion
- Pyometra
- No visible signs in bulls
Trichomoniasis is often a herd fertility problem before it looks like an individual animal illness. Many infected cows appear healthy, and infected bulls almost always do. That means the first warning sign may be disappointing pregnancy-check results rather than obvious sickness.
Talk with your vet promptly if you notice repeat breeders, a sudden drop in conception rate, more open females than expected, or a calving season that keeps stretching later. Those patterns deserve investigation because trichomoniasis can spread quietly through natural breeding groups.
What Causes Trichomoniasis in Cows?
Trichomoniasis is caused by Tritrichomonas foetus, a microscopic protozoan parasite. In cattle, it is considered an obligate venereal pathogen, meaning it is mainly maintained and spread through breeding. The most common route is natural service from an infected bull to a cow or heifer, and then back to other bulls and females during the breeding season.
Bulls are especially important in disease spread because the organism can live in the folds of the prepuce without causing obvious illness. Older bulls are at higher risk of becoming chronic carriers because those folds become deeper and more complex with age. Younger bulls may be less likely to remain persistently infected, but they can still become infected and spread the organism.
Cows and heifers usually carry the infection for a shorter time than bulls. Many females clear infection after several months of sexual rest, but during that time they may experience infertility, delayed conception, or pregnancy loss. Immunity after infection is not long-lasting, so reinfection can happen if infected bulls remain in the herd.
Risk goes up when herds use natural service, share or lease bulls, buy mature bulls of unknown status, have fence-line breeding contact with neighboring cattle, or mix breeding groups without testing. In many operations, one infected bull can affect a large number of females in a single season.
How Is Trichomoniasis in Cows Diagnosed?
Diagnosis usually starts with a herd history and reproductive pattern review. Your vet may become suspicious when there are repeat breeders, lower conception rates, more open cows at pregnancy check, or a prolonged calving season. Because bulls are the main long-term carriers and usually have no symptoms, testing often focuses on the bull battery first.
The preferred sample in bulls is preputial smegma or a preputial scraping/wash, collected carefully by your vet and submitted for PCR or culture, depending on state rules and laboratory protocols. PCR is widely used because it is fast and sensitive, but testing requirements vary by state, sale type, and movement rules. Some states require official identification, approved collectors, specific transport media, or repeat testing intervals.
Cows can also be sampled in some situations, but female testing is generally less practical for herd screening because infection may be temporary. In many real-world herd investigations, your vet will combine bull testing with pregnancy diagnosis, breeding records, and review of biosecurity risks such as leased bulls or recent additions.
If trichomoniasis is confirmed or strongly suspected, your vet may also recommend checking for other causes of reproductive loss. A complete workup can include breeding soundness exams, semen evaluation, pregnancy exams, and testing for additional infectious reproductive diseases so the herd plan matches the full picture.
Treatment Options for Trichomoniasis in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm visit with your vet to review breeding records, pregnancy rates, and recent cattle introductions
- Targeted PCR testing of higher-risk bulls, especially mature, leased, borrowed, or newly purchased bulls
- Pregnancy checking and culling open cows when appropriate
- Immediate separation from breeding groups and removal of confirmed positive bulls from natural service
- Short breeding season planning and use of virgin replacement bulls when feasible
Recommended Standard Treatment
- Whole-herd reproductive review with your vet
- Official trich testing of all herd bulls according to state and lab requirements
- Breeding soundness exams before turnout, often including semen evaluation and trich sampling
- Removal and culling of all positive bulls
- Pregnancy diagnosis of exposed females and culling or management of open cows based on herd goals
- Biosecurity plan covering purchased bulls, fence breaches, commingling, and bull isolation after testing
Advanced / Critical Care
- Full herd-control program designed with your vet and, when needed, state animal health officials
- Testing of all breeding bulls plus repeat or official follow-up testing where required
- Aggressive culling and complete bull battery replacement with virgin or verified test-negative bulls
- Defined breeding season, strict post-test isolation, and no shared or leased bulls
- Expanded diagnostics for other reproductive diseases and infertility causes
- Use of artificial insemination or closed-herd breeding strategies where practical to reduce future venereal disease risk
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Trichomoniasis in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- Based on our pregnancy rates and breeding records, how concerned should we be about trichomoniasis versus other reproductive problems?
- Which bulls in this herd are highest risk and should be tested first?
- Does our state require official PCR testing, repeat testing, special identification, or reporting for trichomoniasis?
- Should trich testing be done at the same time as each bull’s breeding soundness exam before turnout?
- If a bull tests positive, what are our realistic management options for the rest of this breeding season?
- How long should exposed cows or heifers be managed before rebreeding, and when should we pregnancy check them?
- Should we cull open cows now, or are there situations where holding them makes sense for our operation?
- What biosecurity changes would most reduce our risk when buying, leasing, or sharing bulls?
How to Prevent Trichomoniasis in Cows
Prevention is centered on keeping infected bulls out of the breeding herd. The most reliable steps are to use virgin bulls when possible, test mature or non-virgin bulls before turnout, and avoid sharing, leasing, or borrowing bulls unless your vet confirms they meet current testing requirements. In many areas, annual bull testing 60 to 75 days before breeding is a practical part of herd reproductive planning.
A defined breeding season also helps. It makes pregnancy checking more useful, helps identify open cows sooner, and gives cows that were exposed time for sexual rest if needed. Your vet may recommend pregnancy diagnosis followed by culling open cows, especially in herds with confirmed infection or poor reproductive performance.
Good biosecurity matters at the fence line too. Fence breaches, commingling with neighboring cattle, and buying older bulls of unknown status can all reintroduce disease. If a tested bull has contact with females or cattle of unknown status after testing, your vet may advise retesting before turnout.
Vaccination has limited benefit and is not a stand-alone solution where available. For most U.S. herds, the core prevention plan is still testing, culling positive bulls, using low-risk replacements, and tightening breeding management. Your vet can help tailor that plan to your herd size, breeding system, and state regulations.