Vet Advice

Tritrichomonas foetus can cause significant reproductive losses in affected cattle herds. Trichomonas, found in North and South America, South Africa, and Australia, is a "true" venereal disease. That is, infected cows and infected bulls spread it during breeding. One infected bull can infect every cow he breeds. Breeding an infected cow infects bulls.

The trichomonas organism is fragile and does not live outside the reproductive tracts of cattle. The organism is a three-haired flagellated protozoa. It is motile and about two to three times the size of a red blood cell. It is single celled and multiplies by binary fission. The organism has a low ability to invade tissue. Therefore, inflammation of the cervix and placenta are minimal in the cow.

The mechanism of abortion is not completely understood. Bulls do not mount an effective immune response against trich. They do not show any outward signs of infection. They continue breeding and produce normal sperm. Bulls carry the organism in the folds (epithelial crypts) of the prepuce and penis. Young bulls are less likely to become permanent carriers than older bulls because the folds or crypts are less developed in younger bulls.

A few "virgin" bulls have tested positive on occasion, possibly having been exposed in an unknown infected herd. Bulls older than four years become permanent carriers. Younger bulls can get rid of the infection but the time required varies. Testing bulls is not 100 per cent accurate but you can get close with additional testing: after one test, 85 per cent accuracy; after two tests, 95 per cent accuracy; after three tests, 99 per cent accuracy.

The most common symptoms of affected cow herds are repeat breeding, low pregnancy rates and many late calves. Affected herds can experience open rates of anywhere from 11 to 84 per cent at preg-check time. Cows infected with trich become pregnant and then abort. Usually they abort 15-80 days after they have been bred but they can abort later in pregnancy. After three to five heat cycles, a cow develops a natural immunity to the organism, and can conceive upon subsequent breeding, and carry a calf to term. About two per cent of these cows can calve normally but still spread infection when exposed to bulls the next breeding season. These cows can carry the organism up to nine weeks after calving. Any aborted calves or pyometra (infected uterus) should be checked by your veterinarian.

What do you do if you suspect your herd is exposed?

Bulls

• Test all bulls presently owned and newly acquired bulls.
• Ensure these "clean" bulls don't contact infected cows.
• Use of "virgin" yearling or two-year-old bulls minimizes chances of bull infection.
• Don't loan or rent breeding animals.
• Keep bulls and cows separate except at breeding time.

Cows

• Purchase replacements as virgin heifers or buy cows from reliable herds (with vaccine and conception history).
• Cull all open cows and heifers.
• Maintain good fences so herds don’t mix.
• Keep to a maximum 90-day breeding period (problems show up sooner if breeding periods are shorter).
• If using AI, check if the semen center tests for trichomonas. The organism may survive the freezing process used by the stud.
• Control other reproductive diseases with vaccines (such as IBR, BVD, vibrio). This makes it easier to spot trich when it arrives.

Community pastures warrant unique recommendations. Everyone who uses a community pasture must comply with these type of restrictions, since the chain is only as good as its weakest link.

• Test all bulls if a problem is suspected with pregnancy rates.
• Test all new bulls regardless of age.
• Keep bulls in the same pasture or with the same cows all breeding season, don't move them around to different pastures.
• Allow only cows that have successfully calved and have the same calf at foot into the pasture.
• Do not expose cows to bulls before they enter the pasture.
• If patrons want to breed before entering the pasture, put these cows in a dry field away from the unbred ones.
• If bulls are owned by separate patrons, get the bulls tested for trichomonas before each breeding season.
• Maintain good fences.
• Vaccinate for other reproductive diseases.

Promote the idea that all patrons have to be concerned and try to do all they can for the common good.