Seeking harmony on trich standards

 Resize text         Printer-friendly version of this article Printer-friendly version of this article

At the Trichomoniasis Forum last week in Omaha, much of the discussion centered on standardizing testing protocols and state regulations for testing cattle shipped between or within states. Currently, 22 states have some regulations regarding testing cattle for trichomoniasis or “trich,” but the specifics of those regulations vary. That variation can complicate cattle marketing, particularly for seedstock producers who sell bulls to customers in multiple states. In some cases, transport of purchased bulls can be delayed by several days while the seller arranges for appropriate testing based on the bulls’ destinations.

Discussion points included several specifications that differ between states with trich regulations.

Age for testing

Some states specify that imported bulls over 12 months of age must be tested, others specify up to 24 months. Some participants maintained that older bulls could be verified as virgins and shipped safely without testing. Others argued that more advanced age increases the likelihood a bull has had contact with females, either intentionally or unintentionally.

Duration of test

Some states have required bulls to be shipped within 30 days of testing, others allow up to a 60-day window from the test to the shipping date. There was general agreement among participants that 60 days provides greater flexibility for the seller and can achieve program goals, provided the bulls have no contact with females during that time.

Pooled versus individual samples

Currently, 11 states of 22 with trich regulations allow laboratories to pool samples from up to five bulls for a single PCR test. If the laboratory finds a positive result in a pooled sample, they can go back and test individual samples to identify the infected bull. This reduces the cost of the PCR test to the producer, but with a small decline in accuracy. Representatives from ThermoFisher Scientific, formerly Life Technologies, outlined a recent study, published in the Journal of Veterinary Diagnostic Investigation comparing the sensitivity of pooling trich samples with individual samples. The study, led by Lee Effinger from the Oregon State Department of Agriculture involved five feeder diagnostic labs in different states running there, with the Kansas State Veterinary Diagnostic Laboratory serving as the central study lab and analyzing the same samples. The researchers found pooling at 1:5 missed 4 percent of T. foetus positive samples and 1:3 pooling missed 3.5 percent of positive samples.

Several forum participants maintained that pooled testing encourages more producers to test more bulls, a benefit that overshadows the small decline in accuracy. Others favored individual testing, arguing the potential cost of an infected bull slipping through the system justifies investing in the most accurate method available. 

PCR versus culture tests

Diagnostic laboratories have, in recent years, increasingly shifted toward the polymerase chain reaction (PCR) test, rather than the culture method. Tiffany Bergner, DVM, with the Colorado Department of Agriculture, said her lab used the PCR test on 82 percent of trich samples in 2013. There was general agreement though, that states should not mandate a specific test, and should keep options open for emerging technologies. Bergner, for example, says her lab is evaluating the new “Xtreme Chain Reaction” or XCR test from Fluoresentric, which can complete a trich test in 25 minutes, compared with about 90 minutes for real-time PCR, three hours for conventional PCR and five to six days for culture tests. Also, systems for on-farm testing likely will become available in the future and regulations should allow for their adoption once accuracy is proven.

Sampling and shipping protocols

Jeff Ondrak DVM, MS, from the Great Plains Veterinary Educational Center, presented a general outline of trichomoniasis, including the challenges of testing. He notes that errors can occur at the pre-analytical phase, such as when samples are improperly collected, labeled or handled, at the analytical phase with technician errors or faulty equipment, and at the post-analytical phase, primarily through reporting errors. Ondrak notes though, that reports from human medicine indicate up to 90 percent of diagnostic test errors occur in the pre- and post-analytical phase of testing, while less than 10 to 13 percent of the error occurs during the analytical phase.

Tritrichomonas foetus samples need to be stored and shipped within a temperature range of about 60 to 98 degrees Fahrenheit, according to diagnosticians presenting at the conference. The label on the Biomed TF Transit Tube specifies a narrower temperature range 18 to 25 degrees Centigrade (64 to 77 degrees Fahrenheit). Specifications for how soon the samples should be shipped vary between states and individual laboratories, and different labs have different tolerances for samples contaminated with blood or other foreign material or samples in expired transit pouches or tubes. Texas A&M veterinarian Tom Hairgrove says that in Texas, labs will analyze contaminated samples, but only for diagnostic purposes and not to meet regulatory requirements. In Colorado, Brigner says labs had to “put their foot down” and notify veterinarians and producers they would no longer accept expired pouches or tubes. Brigner also says her lab prefers veterinary clinics do not incubate and freeze samples, but instead send them directly to the lab for incubation. Some other states and labs are comfortable with frozen samples

Most participants seemed to agree that some variation between laboratory protocols and policies is understandable and acceptable, based on differences in their facilities, staffing and other factors.

Texas A&M University provides offers online videos demonstrating how to properly collect and submit trich samples to a diagnostic laboratory. 


Prev 1 2 Next All



Comments (0) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left