Trich is a venereal disease of cattle that has caused significant economic losses in American cattle herds for many years.
Trich is a single-celled protozoan that reproduces by binary fission. There are many
different types of other protozoa in the same family of organisms. It is pear-shaped
and roughly the size of a head of a bovine sperm cell.
It is characterized by three flagella (whip-like processes) at its front, and a wavy membrane over its entire length which ends in a posterior flagellum. This protozoan has an affinity for cattle.
Bulls infected by trich are entirely without symptoms. Semen quality and sexual
behavior are not affected. In bulls, the organism is only found on the penis and
membranes inside the sheath. Microscopic folds within the skin surface of the penis
and sheath are sites for localization of the organism. Because these crypts become
deeper as the bull ages, there is a definite association between age and infection.
Infection of the cow takes place at breeding. After the protozoa attach to the lining
cells of the vagina, they form colonies which spread to the uterus and Fallopian
tubes. The uterus reacts to this colonization with an inflammatory response.
Trich is a venereal disease of cattle that has caused significant economic losses in
American cattle herds for many years. Its return to prominence in South Dakota in
2004-2005 is contrasted by the long-standing more endemic nature of the disease
in other western states.
The rate of diagnosis of trich in the region has increased in recent years; whether this is due to an actual increase in numbers of affected herds or simply heightened awareness of the disease is not clear.
Economic losses in affected herds occur due to smaller and less uniform calf crops,
costs of culling and subsequent replacements, and increased veterinary expense.
Models have put the drop in income from the presence of trich in a herd at 22-37%.
In 2000, a group of Colorado producers figured the impact of trich in their herd at
$143.17 per cow. Some estimates of the national loss due to this disease are as
high as $650 million. The costs would be higher in the current market.
Trich reproduces by budding or an asexual fashion. Veterinarians describe it as an
exponential type disease. It can go from one to literally hundreds of thousands and
even millions within a few weeks.
Idaho was among the first to put forth regulations on trich. Prior to that, an estimated 16% of bulls there tested positive for trich. Now, 1-2% test positive and through the state office, all bulls must be tested each year. In Arizona, all bulls coming into the state must be tested.
The overall herd effects of trich in cows can be summarized in this way:
1. Poor pregnancy rates when bulls are pulled from pasture in a timely manner.
2. Spread-out calving season/late-calvers, especially when bulls are left in to breed for an extended time period. This may be seen in conjunction with an increased number of open cows; a majority of pregnancies do not correlate with the start of breeding season.
3. Abortions and infected cows carrying dead fetuses.
4. Returns to estrus on pasture. If careful observation takes place, an abnormal number
of cows returning to estrus in the middle of the breeding period may be noted.
Overworked, tired bulls may be an indirect indicator of this.
Trich is a disease with a long history in the American West that has caused
immeasurable economic loss to the beef industry over the years. It is only through
understanding the disease and the responsibility and role in controlling it that
stockmen can greatly lessen the impact it has on future generations of cattle