Post by kansasdexters on Oct 28, 2010 7:53:23 GMT -5
There has been much discussion on testing Dexter cattle for genetic conditions such as PHA and Chondrodysplasia, but very little discussion on testing animals being brought into a herd for common cattle diseases such as Bovine Viral Diarrhea-Persistent Infection (BVD-PI), Bovine Leukosis Virus (BLV), Blue Tongue Virus (BTV), Anaplasmosis, Johne's Disease, Leptospirosis, and for sexually transmitted diseases such as Trichomoniasis and Vibrio.
Many naive breeders will bring untested breeding stock into their herd without doing any testing for disease and/or without requesting vaccination records and history. They rely only on an interstate health certificate (which may or may not require TB or Brucellosis testing) and assume that the new animal doesn't carry any disease that may harm their existing herd. In addition, many large animal vets are not trained as viralogists and they are not experts on recommending which tests to use or even how to interprete the results. As a consequence of this, when a screening test comes back with a detect (a positive test result), the vet will seldom recommend doing a follow-up, definitive test to make sure that the first test wasn't a false positive result.
Because we've done extensive testing on our cattle, we have had the experience (more than once) of getting a false positive on a screening test, and then having to request a retest using a different and more definitive method, and then having to confirm the retest in order to invalidate the first test's false positive.
Some of the common screening tests are ELISA tests. ELISA stands for Enzyme-Linked Immunosorbent Assay. ELISA tests rely on antigen-antibody interactions and frequently these tests also rely on a color change to indicate that an interaction has taken place. These are very sensitive tests and they are highly specific, but they are not foolproof, and false positives may occur for a number of reasons. If the same test is repeated on the same sample, the result may be the same -- but it may be wrong!
I bring this up because we have had several ELISA tests come back with false positive results for BLV, BTV, and for anaplasmosis. Follow-up tests confirmed that the animals were actually negative for these diseases and that the ELISA test results were invalid. But the time and expense of doing this additional testing has been significant. Our vet did not realize that these screening tests were not the "final diagnosis" and that additional testing was warranted on animals that tested positive.
Because of my laboratory and testing experience, I understood the limitation of these screening tests, and I knew to ask for the follow-up test(s). But, if I had not requested the follow-up, definitive testing, we would have made the wrong decision about the animal's health and need for treatment or not.
Thought it might be of benefit to this group to get some discussion going on this topic.
Patti
Many naive breeders will bring untested breeding stock into their herd without doing any testing for disease and/or without requesting vaccination records and history. They rely only on an interstate health certificate (which may or may not require TB or Brucellosis testing) and assume that the new animal doesn't carry any disease that may harm their existing herd. In addition, many large animal vets are not trained as viralogists and they are not experts on recommending which tests to use or even how to interprete the results. As a consequence of this, when a screening test comes back with a detect (a positive test result), the vet will seldom recommend doing a follow-up, definitive test to make sure that the first test wasn't a false positive result.
Because we've done extensive testing on our cattle, we have had the experience (more than once) of getting a false positive on a screening test, and then having to request a retest using a different and more definitive method, and then having to confirm the retest in order to invalidate the first test's false positive.
Some of the common screening tests are ELISA tests. ELISA stands for Enzyme-Linked Immunosorbent Assay. ELISA tests rely on antigen-antibody interactions and frequently these tests also rely on a color change to indicate that an interaction has taken place. These are very sensitive tests and they are highly specific, but they are not foolproof, and false positives may occur for a number of reasons. If the same test is repeated on the same sample, the result may be the same -- but it may be wrong!
I bring this up because we have had several ELISA tests come back with false positive results for BLV, BTV, and for anaplasmosis. Follow-up tests confirmed that the animals were actually negative for these diseases and that the ELISA test results were invalid. But the time and expense of doing this additional testing has been significant. Our vet did not realize that these screening tests were not the "final diagnosis" and that additional testing was warranted on animals that tested positive.
Because of my laboratory and testing experience, I understood the limitation of these screening tests, and I knew to ask for the follow-up test(s). But, if I had not requested the follow-up, definitive testing, we would have made the wrong decision about the animal's health and need for treatment or not.
Thought it might be of benefit to this group to get some discussion going on this topic.
Patti
It seemed a good time to revive it! I see these diseases mentioned on KFC, almost always in relation to dairy cattle. However, a cow is a cow, right? So that raises several questions:
