Regulation changes not to blame for Montana trich outbreak

News
May 4, 2012

An outbreak of trichomoniasis in central Montana has producers, local veterinarians, and officials with the Montana Department of Livestock (MDOL) working rapidly to contain the disease and lessen the impact to area ranchers. Thus far, MDOL personnel have identified 40 positive bulls, across eight herds, primarily in Fergus and Musselshell counties, says state Veterinarian Marty Zaluski.

Ironically, the outbreak comes in the wake of recent relaxation in the regulations governing where and when bulls must be tested in that state.

Trichomoniasis, or “trich” is a venereal disease of cattle caused by a parasitic protozoan. A bull that carries the disease typically exhibits no adverse symptoms. In cows, however, trich leads to early embryonic death, uterine infections and temporary infertility. Trich can have profound economic effects to a cow herd, lengthening the calving season, causing abortions, and reducing conception by as much as 50 percent in a single year. Nationwide, it is estimated that the economic costs of trich exceed $100 million annually. While a vaccine is available to aid in clearing the disease from infected cows, a vaccine does not exist to prevent the disease in either cows or bulls.

Due to the potential economic effects of the disease, most western states in recent years have developed trich regulations in an effort to prevent infections from spreading. While individual rules vary from state to state, all rely heavily on testing bulls as the primary reservoir for the disease. Until last year, Montana’s trich program required that every bull sold in the state, as well as those brought in from elsewhere, be accompanied by a negative trich test from a certified veterinarian. Beginning in 2012, however, MDOL reduced that requirement, focusing instead on four counties where trich was known to be a persistent problem. Bulls inside this “epizootic area” must still be tested prior to sale. However, under the new program, testing is only required at the statewide level in cases where bulls are being released onto ranges grazed commonly by multiple operations. As in most western states, testing is still required on all bulls imported from out of state. Any bulls found to be carrying trich must be removed from the affected herd, and cows exposed to those bulls quarantined for 120 days.

According to Zaluski, maintaining the original program likely would not have prevented the current outbreak. “This outbreak was picked up initially by a rancher that had low conception rates last fall, and wanted his bulls tested,” said Zaluski. “It wasn’t any of our regulations that detected it, it was a conscientious producer who wanted to do the right thing.” Producer rather than departmental detection of trich in Montana is commonplace, says Zaluski. So much so that it was one of the deciding factors in altering the previous program, a change requested by producers due primarily to that program’s hefty price tag. “Even when we had a statewide program, the actual regulations only picked up the minority of trich positive herds identified,” said Zaluski. “If we’re finding trich in a fairly specific geographical area, and our regulations haven’t been that effective at picking up the disease in the first place, why create those costs?” Following the initial outbreak, says Zaluski, subsequent testing of neighboring herds, a virtual requirement under the new program, turned up the additional cases. At this point, he says, it is not possible to determine the actual source of the outbreak. “Identifying the causality of these things is really tricky,” he points out. “The folks that pick up the trich are as often victims as anything else. At some point, they got infected from another source.” Zaluski adds, “A number of things come together to cause an incident like this.

There is a history of producers conducting some riskier practices, and the fact that we’ve found this many herds affected may indicate that folks haven’t been testing as proactively as possible in retrospect.”

While trich is not preventable, stresses Zaluski, there are several management practices that producers can use to lessen the risk of exposure. Good fence maintenance is one of the simplest steps, he says, as is the practice of keeping track of when and where a producer’s cattle commingle with others that may be carrying the disease. Older bulls are more prone to harboring the disease, so the use of younger bulls, and/or periodic testing of bulls, can also lessen the risk. Another good practice, he says, is the rapid culling of open cattle after the breeding season. While the effects of a trich infection at the start of breeding can be immediate and severe, the effects of a late season infection can be harder to identify. “If the trich exposure happens late in the season, a lot of the females may already be pregnant; therefore, your impact on pregnancy rate that season can actually be very small,” says Zaluski. “A producer may think that they are out of the woods, but some of those open cows or the bulls may be positive, and that will really whack you in the next season.” Additionally, he points out, any case where a large number of cattle are observed in heat following breeding, or a higher percentage than normal are found to be open following preg checking, trich should be considered as a possibility.

With regard to the current outbreak in central Montana, a meeting was held last week with producers to discuss methods to curb the spread of the disease in the affected area. “The meeting was very well attended,” says Zaluski. “Folks were very interested in getting after this, and they’re serious about getting rid of it.

That makes our job a lot easier,” he adds. “This disease can really make the difference between a profitable operation and one that can’t make it to the next season.” — Jason Campbell, WLJ Correspondent

{rating_box}