Trichomoniasis is a reproductive disease which results in early pregnancy loss and open cows at the end of the year. The first thing a producer might notice is cows returning to heat when they should be pregnant. This sexually transmitted disease is caused by protozoa that live in the reproductive tract of cows and sheath of bulls. It occurs most often when ranchers use untested bulls, purchase open cows with unknown background, or when cattle herds commingle during breeding season.
University of Saskatchewan research scientist Bart Lardner says it’s wise to test bulls before or after breeding season, especially in community pastures. If producers have a closed herd and don’t buy new cattle, this disease may not be an issue unless a neighbour brings in new cattle and an infected cow or bull comes through the fence.
“Having your bulls tested prior to the next breeding season can be very important if there is any chance they may have become infected,” Lardner says. “Often producers don’t have a clue they have trich in their herd until they have a lot of open cows in the fall, or some cows cycle all summer long and don’t conceive. Sometimes a producer is not aware of the possibility of this disease when bringing in a new bull, but it’s wise to check bulls.” There is also risk when buying open cows. Unless it’s a virgin heifer, any open female could be carrying this disease.
Anyone borrowing, leasing or buying a used bull (rather than a virgin bull) should have that bull tested before using him. “You don’t want to bring in any reproductive diseases,” Lardner says.
Even though testing bulls is not mandatory in Canada as it is in many western U.S. states, most community pasture associations require testing, and require cows coming in to have a calf at foot (showing they were able to carry a calf and are probably not infected).
Risk in community pastures
Community pastures where multiple herds are commingled are among the highest-risk situations for trich to be passed from infected bulls to cows, and then from infected cows to other bulls. However, cattle mixing between herds due to fenceline problems can also lead to herd outbreaks.
There are a couple of testing methods. For many years the only way to check for trich was to take a sample from the bull’s sheath and culture it. This gives a 90 per cent chance of finding the organism if the bull is infected. Standard practice is three cultures, one week apart. If they all come up negative there is only one chance in 1,000 that the bull is infected. Today, however, many veterinarians and producers choose a PCR (Polymerase chain reaction) test, which is more accurate, and faster.
These DNA tests are becoming more affordable, and speed things up, especially if a producer needs test results and turnout is approaching. Producers who graze community pastures are still encouraged to start testing 45 days before turnout. Even though PCR tests don’t take as long, they must be a week apart. You want to make sure every bull is clean before turnout.
It is difficult to eradicate this disease. In spite of the fact that most western states have rules and requirements for testing, trich continues to show up, and this will probably also be true in Canada. Most western states require testing of bulls prior to sale. If infection is found in a herd there are quarantines — always the bulls, but in some cases cows. In spite of this, the disease continues to appear.
Some stockmen don’t test bulls, and may purchase cattle with unknown history. This puts their neighbours’ herds at risk if cattle mingle on public pastures or a bull goes through a fence to breed the neighbour’s cow, or an infected cow gets into the neighbour’s place and is bred by the the bull, which becomes infected.
There is no good test for females. A small percentage of females can act as carriers. Open females and cows that calve late in a herd should be culled.