Updated April, 2011
Trichomoniasis (Trich for short) is a venereal disease of cattle. Trich is caused by a protozoan organism Tritrichomonas fetus. Trich is one of the most costly diseases today’s beef producers face if exposed. Trich also affects dairy cattle but due to differences in management it is generally easier to control on dairy farms. Trich is more common in our western range cattle due to management practices and common grazing allotments. Most western states now have Trich control programs in effect to limit the damage caused by this disease. It is important to know that these are only control programs and not eradication programs and therefore we need to stay alert for signs of Trich in our herds.
The organism lives in the prepuce of bulls and the uterus and vagina of cows. The disease is spread from infected animals by sexual contact during breeding. The organism causes no clinical signs in bulls, but they can be carriers for years. When a susceptible cow is exposed to Trich during breeding she will conceive as normal but the fetus and fetal fluids remain infected with the organism. The most common scenario is for the cow to absorb or abort the fetus prior to 3 months gestation, and most all lose the fetus prior to 5 months. These cows are then open and will cycle back; hence one of the indicators of Trich in a herd is seeing cows return to estrus after it appeared that most of the cows were bred. Trich also causes a few late term abortions but this is less common than early embryonic death. When introduced into a susceptible herd Trich can be the most economically devastating disease facing the cattle producer. If introduced early in the breeding season, the rapid spread of Trich can lead to 40% to 60% open cows at preg check time.
The best way to control Trich is by purchasing virgin bulls and preventing mixing of cattle with other herds. If you raise heifers, purchase Trich free bulls, and don’t have any sexual contact with other herds, your cows will be Trich free. This sounds easy but for many of our western herds it is not practical. Trich control programs can be quite varied, as they say there is more than one way to skin a cat, and what works for one producer may not be practical for another.
Maintaining fencing to prevent or limit mixing is the first step in prevention. We may not be able to eliminate mixing due to our vast ranges and common grazing allotments but we should minimize it when possible. When producers have common grazing allotments, the grazing association should establish rules to reduce the chance of Trich within the allotment. Working with your veterinarian and the other members of a grazing association is the first step in reducing or eliminating this costly disease.
Testing bulls for Trich goes a long way as an insurance policy to help eliminate the financial hardships caused by Trich. If bulls are Trich free when introduced to cows the hope is that most cows will be bred before Trich has a chance to increase to high levels. In our experience the first year Trich is introduced into a herd it lowers conception rates, which costs producers money, but we usually don’t see the big wrecks that are commonly associated with Trich. When Trich positive bulls are turned out at the beginning of the breeding season it is spread fast and the 40% to 60% conception rates that have put some producers out of business are much more common. Any herd that does not operate as a closed herd should test bulls prior to the breeding season. The optimum time to test is 10 to 30 days after being removed from the cows. If a herd maintains spring and fall calving cows they should test bulls twice yearly; after removal from each group, and prior to each breeding season. The cost of Trich testing is well worth the peace of mind.
Vaccination is another commonly used tool. I have heard rumors that vaccination is “totally worthless” to rumors that “by vaccinating twice yearly you can eliminate Trich even if you don’t do anything else”. In our experience vaccination has been beneficial; and like the testing of bulls, it usually helps to prevent the big wrecks. Vaccination of cows has helped prevent the big wrecks in our clinic but it is not uncommon to see conception rates 5% to 15% below expected in exposed and vaccinated herds. Conception rates are probably unchanged by vaccination of bulls but in our experience in exposed herds we find less positive bulls in exposed herds if they are vaccinated; this reduces the cost of replacing bulls. Vaccination currently costs about $3 to $3.50 per head and, although expensive, it is recommended if there is a significant chance of exposure. On the other hand, it is probably not cost effective if your chances of exposure are slim. The vaccine is the most effective when given two to four weeks prior to the breeding season. The more this time is extended the less effective the vaccine becomes. Therefore, we should give the vaccine as close to this window as possible, in order to get the most bang for our buck.
Other control procedures deal with management. Pregnancy testing of cows allows for the removal of open cows. By removing open cows we remove the most likely cows affected with Trich. When a herd has been infected with Trich we are often asked about keeping open cows. If open cows are kept for rebreeding they should have 60 days (3 heat cycles) following preg check to give them the best chance to clear the disease prior to rebreeding. We also recommend managing this group separately and testing bulls after the breeding season. We also recommend using older bulls on this group so if one comes up positive it will be less of a loss to the producer.
One of the most effective steps in managing Trich is to work out pairs after calving and only put bulls with cows that deliver a live calf. For those that turn cattle out prior to calving this of course is not possible. In this later situation the best you can do is to only turn out pregnant cattle, preferably past 5 months gestation. Although this is probably the most labor intensive management practice it has been the one tool that gives us the fastest results when trying to eliminate Trich. Only one positive cow in somewhere between 1000 and 10000 infected cows is thought to carry a live calf to term and still be infected. So with rare exceptions we can eliminate Trich in one year by turning out clean bulls with cows that carried a live calf to term. If we are unlucky and this does not work the first year, the odds are really in your favor the second year.
Note this last management procedure is different than simply preg checking cattle and then turning the bulls in after calving, which is the more common practice. Cows that abort following preg check may not have time to clear the infection prior to breeding. These cows will often be the first ones to breed causing the infection to spread at the beginning of the breeding season. By putting clean bulls with pairs we eliminate this risk.