Chi-man,
Been there, feel your pain.
Crossbred commercial herd here, no registered cattle - but, we like 'em just the same.
Was losing one cow a year, to lymphosarcoma, for several years running, and wife finally said - we've gotta figure out where we stand with this deal, so we bled the entire herd, in 2007. 40 of 44 adult cows were BLV positive; 1 of 4 yearling heifers was positive, 1 of 10 weanling heifers were positive. So... 90% infection rate in the adult cows; I'd have been all but out of business if I'd culled all positives, and would have lost most of my best genetics.
Since that day, any heifer, or cow/heifer that tested negative at that time has not been stuck with a needle that has been in another animal, and every animal gets their own disposable OB sleeve when palpating for pregnancy or AI-ing; no in-and-out of any bottle of vaccine/medication with a needle that has been in an animal.
I have not gone back and re-bled the herd (yet) to see if I've made any headway with regard to protecting herd additions - but all the scientific literature I've read indicates that if you have a herd infection rate in excess of 40-60%, it will be virtually impossible to 'clean up' the mess without separating them into 'infected' and 'non-infected' herds, which are run and managed separate from one another. May do another whole-herd test of every female over 6 months of age this spring. Or, maybe not.
There is no doubt in my mind that I spread this infection throughout my herd by re-using needles on multiple animals. Disposable needles are CHEAP; yeah, it's a pain in the butt to change needles for every animal(I will, however, reuse needles on steers and known BLV+ animals), but it's the RIGHT thing to do. BLV is in the same class with HIV - we all know how concerned the human medical community is about needle sticks and exposure to blood - we need to have the same concerns with regard to our cattle.
It's an infection that is more widespread than most people realize. Good overview here, even though the info is nearly 20 yrs old:
http://www.aphis.usda.gov/animal_health ... is_BLV.pdf
Only 5-10% of infected cattle will go on to develop lymphosarcoma or leukemia - but there's no way to predict which ones will. I did not liquidate the herd, or even the seropositive animals. Planned to sell all seropositives once they hit 10 yrs of age, but have not held to that - some of those old, original cows are our best producers - but I look for any reason to send those known infected cows down the road - one strike, and they're gone. Have not lost a cow to lymphosarcoma since 2007.
Aaron,
False positive test results for BLV are not a problem, in animals over 6 months of age. It's a very sensitive and specific test.
Cost? $4.50/animal at the diagnostic laboratory where I work. May be more or less expensive at other laboratories.
