As beef herds consider their bull battery for subsequent breeding seasons, herd health and reproductive disease should be important considerations.
Perhaps the one reproductive disease for which the bull plays a critical role in transmission is that of trichomoniasis, or “trich.” This disease has been around for generations and for many years was thought to be something only states west of the Rocky Mountains had to concern themselves with.
That changed for South Dakota cattle producers back in 2004, when over 40 herds were detected with the disease and were faced with the task of cleaning it up. A cooperative effort between the South Dakota Animal Industry Board and cattle producer organizations resulted in the implementation of regulations that not only tackled importation of the disease, but also its spread within the state. These regulations involve testing of all non-virgin bulls moving into the state or between herds, as well as the prohibition of open cows being sold back into breeding herds. While South Dakota has enjoyed several years of very few new infections after those regulations were implemented, a recent resurgence of the disease has brought trich back to the top of producers’ minds.
Causes and detection
Trich is caused by a protozoal organism that lives indefinitely in the sheath of an infected bull. Once it’s transmitted to a female through the act of breeding, it causes an inflammation in the reproductive tract that results in the loss of the pregnancy. While infected cows can clear themselves of the infection, bulls remain positive for life. Therefore, detection strategies for this disease come down to testing the bull.
Animal health professionals have come a long way over the past 10 years in the methods used for detecting the organism. For testing bulls, the preferred sample is still a scraping from inside the animal’s sheath, obtained by a veterinarian. The protozoa lives in that part of the body, protected by the microscopic peaks and valleys in the skin inside the sheath.
Currently, the most popular laboratory testing method is polymerase chain reaction, or PCR. This is a very sensitive diagnostic technique that can detect just a few organisms, as well as those that are no longer living. Prior to the onset of PCR testing, culture was the only way to detect trichomoniasis. The sheath sample was placed in nutrient-rich liquid and allowed to grow before being examined under a microscope. This method has several shortcomings, including the need for the organism in hot or cold temperatures on the way to the lab. Regulations required veterinarians using the culture method to take three samples at weekly intervals from the bull in order to ensure that an infection was not missed.
Improvements in test sensitivity and in awareness of trichomoniasis have significantly reduced the risk of its introduction into our cattle herds overall. However, as recent cases have demonstrated, the disease is a long way from being eradicated – and will remain a consideration for cattlemen for a long time to come.
For current situation reports on trichomoniasis in South Dakota, visit the South Dakota Animal Industry Board website.