Fetal Protection Vaccines (MLV) - Lucky_P

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Ron I can't answer your question but in Australia we only have a killed vaccine for BVD. I don't know the reason for sure but I suspect it is because the authorities here are always windy about allowing the introduction of live vaccines mainly due to the false positives that show up on serology should they want to do any large scale testing. I think a lot of this paranoia stems from the very successfull Brucellosis eradication that we undertook in the 70's and early 80's. All vaccination with Strain 19 was stopped to prevent the false +ve's and then we tested and slaughtered all +ves. Each herd had to have 3 clear tests before declared free.
I think the success went to their heads and now it seems very difficult to get live vaccines in and they usually say it is because it will interfer with testing.
Ken
 
On serologic tests... yes, probably - but if you tested paired sera, you'd likely see a stable, low titer.
On antigen test, like we conduct on ear notches or serum; probably not.
However, the ear notch can be positive in animals which are acutely infected with field strains of the virus.
Vast majority of animals that test positive on whatever PI test is being employed are true PIs, but if you're testing in the face of an 'outbreak', it's conceivable that some positives, say, in a group of stocker/feeder calves with one or more PIs in the mix could be acutely-infected animals.
 
Thanks, Ken and Lucky.

With regard to a vaccine like Bovi-Shield Shield Gold FP (MLV), are the modified virus factions in the serum non-cytopathic or are the viruses cytopathic and they are modified to make them non-cytopathic? I want to know more about why there is fear/risk in regard to MLV specific to the FP vaccines. Rocking P does not use them because of the kinds of problems caused like what happened to me when I vaccinated a pregnant heifer that was thought to be open. Other than going to the vet here in Maysville there is no locally available Bovi-Shield MLV FP vaccines. Vendors say they are concerned that stocking the MLV FP vaccines will make them available to producers who will not use them as prescribed and cause injury to their operations. I want to know about the nature of the antigen (in this case a modified live virus) in a vaccine like Bovi-Shield. What is modified and how is it modified? What risk does it pose? I prefer to use vaccines that illicit the best immune response possible in my cows so I want to use the MLVs. I appreciate insight into what you think you could provide here that would help someone better understand.
 
Ron,
They're non-cytopathic, but attenuated.
I'm 30+ years removed from my undergraduate training in microbiology/virology, so can't speak with any authority on how they're 'modified', these days.
In the past, researchers attenuated some viruses by 'running them through' non-target' species, or growing them in non-target origin cell lines - for example (and I'm just making these scenarios up out of thin air), maybe infecting goats with IBR and re-isolating the virus from the goat or growing BVD virus in baby hamster kidney cell line, etc. For some viruses, growing in an unnatural host lessens virulence.
Or, it may be that the vaccine strains were 'discovered' contaminating certain cell lines, and had lost their virulence after multiple passages in cell culture, or were just innately, a less virulent strain from the outset.

It's close to irrefutable that the mlvs elicit a stronger response in most animals, but the inactivated viral vaccines have come a long way over the past 20 years or so. And, in the hands of folks who may not really know what they're doing, or why...the inactivated products may be best, or at least, may do the least harm.
 

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