While many might not recognize it, trichomoniasis could be the most economically damaging disease cow-calf producers face. A strategic control program, however, can minimize or eliminate the disease from herds. The resulting boost in annual calving percentage can serve to endear a veterinarian to a client, as a relatively small investment can improve ranch returns significantly.
Speaking at last week’s Academy of Veterinary Consultants summer conference, John Davidson, DVM, made those points and others while outlining current research and management practices focused on controlling trichomoniasis, or trich, in cow-calf herds. Davidson, who has practiced in Texas and served on the faculty at Texas A&M University, currently is a senior professional services veterinarian with Boehringer-Ingelheim Vetmidica Inc. and serves as president of the American Association of Bovine Practitioners (AABP).
The trich pathogen, Trichomonas foetus, is a single-cell protozoa, transmitted through sexual contact. In bulls, the protozoa, primarily in a pseudocyst form, adheres to the mucosa in the preputial folds of the penis. There is no cure, and when infected bulls expose cows during breeding, a high rate of lost pregnancies and open cows results. Infected cows eventually can clear themselves of the pathogen, but prior to that, can pass the disease to non-infected bulls in the breeding pasture.
Herds with one or more infected bulls can suffer catastrophic reductions in calving rates of 30% or more. In 1991, Davidson says, trich caused losses estimated at $660 million. Today, as the disease has spread across the country and cattle values have increased, the annual loss is around $1.6 billion.
With bulls the primary source for spreading the disease, bull testing is the most critical and effective means of controlling or eliminating trich from cow-calf herds. Producers should work with their veterinarians to test all their bulls every year, with the exception of purchased bulls already verified as trich free. A veterinarian should test the bulls ahead of breeding season, with enough time to replace any positive bulls. The post-breeding period, Davidson says, offers an opportunity for additional testing and surveillance, in case any bulls became infected during breeding.
Testing involves collecting a sample of smegma from within the bull’s prepuce, and Davidson says the quality of the sample is highly dependent on the skill of the collector. Dexterity on the part of the veterinarian is important in obtaining a good sample with the traditional preputial scraping technique using a pipette. Research has shown, for example, that when a right-handed veterinarian is sampling from the right-hand side of the animal, the likelihood of positive samples increases compared to the same veterinarian sampling from the left side.
Davidson notes that if the sample contains blood, the veterinarian should use a less aggressive scraping technique to minimize discomfort for the bull.
Veterinarians at Iowa State University have developed and tested a less invasive sampling technique, using a gauze sponge to wipe the bull’s penis while collecting semen as part of a bull-soundness exam. ISU tests indicate the method is at least as sensitive as the scraping technique. The wiping method is new, however, and for now, several states specify testing based on preputial scraping to meet regulatory requirements for inter- or intra-state movement of bulls. Veterinarians can use the wiping method for management and surveillance purposes in client herds, but might need to use preputial scraping to comply with regulations regarding bull sales and movements.
Read more about the ISU method in this article on BovineVetOnline.com.
Along with testing all bulls, management factors that can help minimize trich risk on a ranch include maintaining good fences, keeping accurate calving records, isolating or testing imported females, culling open females and maintaining a defined 60- to 90-day calving season. Veterinarians and clients can use an online tool, Trich Consult, to develop a customized control strategy based on the environment, management practices and risk factors at an individual ranch.
Davidson also points out that TrichGuard, the only vaccine approved for prevention of trichomoniasis, can reduce abortion rates and overall disease impact of the disease, especially in high-risk herds. The vaccine cannot by itself eliminate trichomoniasis risk in a herd, but it has demonstrated efficacy in reducing abortion losses in exposed herds. In an Auburn University study, calving rate in vaccinated cattle exposed to trich was 50%, compared with 20% for non-vaccinated cows with the same exposure. In a 200-cow herd, the advantage of 100 calves versus 40 calves added up to a difference of $48,000.