BVD PI

[Dave]

I am raising a bunch of heifers to sell as bred heifers. As one of my selling points I tested them all for BVD PI. It was more of a selling point than actually thinking I would find a PI positive. I just got back the results on the last bunch I tested. I had one positive. Prefectly fine healthy looking heifer but she is PI. Good thing these result came in yesterday, as I am AI'ing the herd tomorrow. She has been through the protocal to sync them but I will skip breeding her. She will go into a seperate pen and get fed out. I found a free martin in the bunch so the two of them can keep each other company all the way to the butcher.

 

[inyati13]

Dave, I am curious, did you recently vaccine this positive heifer with a FP vaccine that included an attenuated or modified live virus, for example, Bovi-Shield Gold FP.

 

[Dave]

Dave, I am curious, did you recently vaccine this positive heifer with a FP vaccine that included an attenuated or modified live virus, for example, Bovi-Shield Gold FP.

Yes I did. Bova Shield Gold. But that was about 4 weeks ago. Are you thinking that it caused a false positive? I will see my vet this afternoon and I will ask him about that. If he thinks it is a possibility I may retest her in a couple weeks. I am thinking I will still skip the AI tomorrow. If it does prove out to be a false positive the clean up bull can take care of her.

 

[milkmaid]

How was she tested? Ear notch, blood test, etc?

The PI tests are really accurate. I even had a calf sick *with* BVD and the test didn't call her PI.

 

[inyati13]

Dave, I am curious, did you recently vaccine this positive heifer with a FP vaccine that included an attenuated or modified live virus, for example, Bovi-Shield Gold FP.

Yes I did. Bova Shield Gold. But that was about 4 weeks ago. Are you thinking that it caused a false positive? I will see my vet this afternoon and I will ask him about that. If he thinks it is a possibility I may retest her in a couple weeks. I am thinking I will still skip the AI tomorrow. If it does prove out to be a false positive the clean up bull can take care of her.

I would check with the vet to get his take. The Bovi-Shield Gold does contain MLV for PI. Depending on whether you can disprove what some are saying, there are those who say the vaccines may result in the animal testing positive and/or having the condition.

PS - I thought it was revealing that stores like Tractor Supply, local feed meals, etc. do not carry MLV vaccines. I ask at the mayslick mill, they told me it is out of concern that people would not be as careful as they need to be on using MLV vaccine for FP they could cause some abortions! Personally, I use them. I am extremely careful and always follow the label instructions.

PS2 - I was just thinking. I have purchased bred heifers from a breeder in my area who tests for the FP panel of organisms. I ask him if they use the MLV vaccines and he said no because it was too dificult in their operation to manage the use of them. I think there are a lot of concerned people who think the use of live or attenuated organisms is going to cause problems. I wish I knew for sure. I worry about it myself but I have used the MLV for all my heifers before breeding.

 

[Lucky_P]

Most(well over 90%) test-positive animals are true PIs, but...
Vaccination with a MLV vaccine containing BVD within three weeks or so of testing may give positive antigen-capture ELISA test results. I'd hazard a guess that 'acute' infection with field strains of BVD would do likewise. Re-testing this heifer in 3-4 weeks would be a reasonable confirmation whether or not she's a PI or was a viremic acute transient infection/vaccinate responder.
The Ag-capture tests detect actual virus in serum or ear notch - not antibodies.
Back when we used to do immunohistochemical staining on ear notches, there was a seminal paper published claiming that you could differentiate PIs from acute/transient infections, based on distribution of virus in the skin/hair follicles. BS. Had a buddy who was working with BVD at UofWY - even experimentally-infected (non-PI) animals were sometimes still positive on ear notches 12-16 weeks out from infection.

 

[inyati13]

Lucky_P, you stated, " Vaccination with a MLV vaccine containing BVD within three weeks or so of testing may give positive antigen-capture ELISA test results." I am wondering why you did not say the vaccine also contained IP, becuase the Bovi-Shield Gold FP also includes the MLV for IP. I wonder if I am missing something! If the animal was tested using a method that is detecting antibodies and not the virus, then, this question comes to my mind: could a vaccine for BVD that was a MLV vaccine produce an antibody response that would provide a positive for PI even when PI is not included in the vaccine? I may not be stating this as clearly as I could.

 

[Dave]

I talked to my vet about it on Friday afternoon. He said with the ear notch which I did it is highly unlikely that the positive came from the vaccination. So I cut her out and didn't breed her with the rest of the heifers. She is in a pen with the free martin. I am thinking that 100-120 days on grain and they will be tasty.

Had a low line angus heifer from down the road show up in my yard Sunday morning. I caught her and put her in the pen with PI and FM until the owner can retrieve her. Sure makes my heifers look good.

 

[Fire Sweep Ranch]

OK, so correct me if I am wrong, but the heifer that is PI, isn't she constantly shedding the virus? And, if that is the case, if any of your other cattle ever get in or near the pen where she is housed, during a certain part of their gestation, can't their calves be born PI also?
That has always been a concern of ours with us showing cattle, the exposure to a PI animal while we have a heifer in that part of her gestation.
Just me, but I would ship that PI heifer in a heartbeat so I have less exposure on my land...

 

[Dave]

OK, so correct me if I am wrong, but the heifer that is PI, isn't she constantly shedding the virus? And, if that is the case, if any of your other cattle ever get in or near the pen where she is housed, during a certain part of their gestation, can't their calves be born PI also?
That has always been a concern of ours with us showing cattle, the exposure to a PI animal while we have a heifer in that part of her gestation.
Just me, but I would ship that PI heifer in a heartbeat so I have less exposure on my land...

You are correct. She is shedding the virus constantly. But where are you shipping her to? The sale and give your problems to others. That would be a bit unethical. I could slaughter her now but she is kind of smallish for that and no finish on her. The rest of the heifers are vaccinated times two and they are out to pasture and won't be around her pen. In fact in two weeks they will be in a pasture 7 miles away. Only other cow around is the free martin who is her roommate. She has been vaccinated and she sure isn't passing anything to her calf. She is in a pen that otherwise would be empty until next October. Long before October she will be in little white packages.

 

[Fire Sweep Ranch]

OK, so correct me if I am wrong, but the heifer that is PI, isn't she constantly shedding the virus? And, if that is the case, if any of your other cattle ever get in or near the pen where she is housed, during a certain part of their gestation, can't their calves be born PI also?
That has always been a concern of ours with us showing cattle, the exposure to a PI animal while we have a heifer in that part of her gestation.
Just me, but I would ship that PI heifer in a heartbeat so I have less exposure on my land...

You are correct. She is shedding the virus constantly. But where are you shipping her to? The sale and give your problems to others. That would be a bit unethical. I could slaughter her now but she is kind of smallish for that and no finish on her. The rest of the heifers are vaccinated times two and they are out to pasture and won't be around her pen. In fact in two weeks they will be in a pasture 7 miles away. Only other cow around is the free martin who is her roommate. She has been vaccinated and she sure isn't passing anything to her calf. She is in a pen that otherwise would be empty until next October. Long before October she will be in little white packages.

How long does it remain in the soil? That would be my concern. Not sure where I would ship one, but my vet put the fear in us early on a few years ago and all calves born on our place are tested that come from heifers that are shown. That way we know when the calf is young if we have to worry (and dispose).
Another question, even if you vaccinate, does that protect the fetus during that window when they are most likely to become PI if exposed? Maybe Lucky can answer that one.
I am not questioning your decision to keep her, just trying to find out more information. It is something that WE (meaning our place) have to worry about since we travel a lot with our bred yearlings. I am not sure what I would do with one if we ever had one, since we are small and have no where to isolate and feed out. Let's hope we never have to deal with it!

 

[wbvs58]

If she is a PI being with unjoined heifers has been the best place she could have been, they would all have been exposed to her and should have good lifetime immunity due to natural exposure before being joined.
In Australia the recommendations for screening for BVD is to sample a handfull of heifers and check for antibodies to BVD. If they are positive then there must be a PI among them and this is then identified by ear notch test and the rest will not need to be vaccinated. If there is no antibody titre in the sampled heifers then they have no immunity and are vaccinated. Bear in mind we do not have a live vaccine for BVD only a killed vaccine.
The retained heifer group is a good barometer for the BVD status in the herd.
Ken

 

[Craig Miller]

I talked to my vet about it on Friday afternoon. He said with the ear notch which I did it is highly unlikely that the positive came from the vaccination. So I cut her out and didn't breed her with the rest of the heifers. She is in a pen with the free martin. I am thinking that 100-120 days on grain and they will be tasty.

Had a low line angus heifer from down the road show up in my yard Sunday morning. I caught her and put her in the pen with PI and FM until the owner can retrieve her. Sure makes my heifers look good.

Are you not concerned about passing the bvd to your neighbor?

 

[Lucky_P]

inyati,
PI stands for 'persistently infected'. Calves exposed, in utero, to BVD virus, between days 80-140 of gestation, can become infected - for life - but their developing immune system does not recognize the BVD virus as 'foreign', does not mount an immune response against it, and it replicates unhindered, with all body fluids and secretions/excretions containing large amounts of virus.
Not sure what 'IP' you're talking about - do you mean PI3(parainfluenza 3), or IBR(infectious bovine rhinotracheitis, a herpesvirus)? Persistent infection, as encountered with BVD, is not an issue with those two... they both can cause abortion, but not persistent infection, as we view it with regard to BVD.

Antigen-capture ELISA(the test method most commonly used by most 'commercial' labs testing for PI animals - as well as a significant % of AAVLD-accredited veterinary diagnostic laboratories) and immunohistochemical staining of fixed/processed sections of ear notches/skin test for actual presence of BVD virus(antigen) in the tissue or serum(the Ag-capture ELISA we perform can be run on serum or ear notch/skin). Test manufacturers even state that positive test results may occur in animals vaccinated within 3 weeks of testing - but I'll bet that most don't; I suspect that's more of a CYA cautionary statement than anything else.
BVD antibody titers only indicate some prior exposure and response - either by vaccination or exposure to a PI animal or an acutely-infected animal shedding virus. I wouldn't trust, however, a 'natural' exposure to BVD virus to confer lifetime immunity. A measurable antibody titer does not necessarily ensure protection against subsequent exposure challenge.

I'd hazard a guess that >95% of 'positive' animals are true PIs - but the possibility of a recently-vaccinated or recently-infected animal producing a positive test result is out there. If I had a positive reactor in my commercial herd, I'd consider her a PI and do away with her - and that does not mean I'd run her through the sale barn; glad to see that the OP is planning to eat her, rather than dump her on someone else. But, I'd certainly want to make sure that she's penned FAR away from any other cattle. It's unlikely that BVD virus can survive much longer than 3-4 weeks outside the host in the environment or on fomites.
Any other animals exposed to this heifer or her secretions risk infection with BVD virus; at least 25% of stocker/feeder calves I see dead from 'shipping fever' pneumonia have BVD in their lung or gut - are they PIs or acutely-infected animals? I don't know - and in most cases, it's not feasible to attempt to determine that - the producer needs to test remaining animals in an attempt to identify and remove any other PI animals in the group.

 

[inyati13]

inyati,
PI stands for 'persistently infected'. Calves exposed, in utero, to BVD virus, between days 80-140 of gestation, can become infected - for life - but their developing immune system does not recognize the BVD virus as 'foreign', does not mount an immune response against it, and it replicates unhindered, with all body fluids and secretions/excretions containing large amounts of virus.
Not sure what 'IP' you're talking about - do you mean PI3(parainfluenza 3), or IBR(infectious bovine rhinotracheitis, a herpesvirus)? Persistent infection, as encountered with BVD, is not an issue with those two... they both can cause abortion, but not persistent infection, as we view it with regard to BVD.

Antigen-capture ELISA(the test method most commonly used by most 'commercial' labs testing for PI animals - as well as a significant % of AAVLD-accredited veterinary diagnostic laboratories) and immunohistochemical staining of fixed/processed sections of ear notches/skin test for actual presence of BVD virus(antigen) in the tissue or serum(the Ag-capture ELISA we perform can be run on serum or ear notch/skin). Test manufacturers even state that positive test results may occur in animals vaccinated within 3 weeks of testing - but I'll bet that most don't; I suspect that's more of a CYA cautionary statement than anything else.
BVD antibody titers only indicate some prior exposure and response - either by vaccination or exposure to a PI animal or an acutely-infected animal shedding virus. I wouldn't trust, however, a 'natural' exposure to BVD virus to confer lifetime immunity. A measurable antibody titer does not necessarily ensure protection against subsequent exposure challenge.

I'd hazard a guess that >95% of 'positive' animals are true PIs - but the possibility of a recently-vaccinated or recently-infected animal producing a positive test result is out there. If I had a positive reactor in my commercial herd, I'd consider her a PI and do away with her - and that does not mean I'd run her through the sale barn; glad to see that the OP is planning to eat her, rather than dump her on someone else. But, I'd certainly want to make sure that she's penned FAR away from any other cattle. It's unlikely that BVD virus can survive much longer than 3-4 weeks outside the host in the environment or on fomites.
Any other animals exposed to this heifer or her secretions risk infection with BVD virus; at least 25% of stocker/feeder calves I see dead from 'shipping fever' pneumonia have BVD in their lung or gut - are they PIs or acutely-infected animals? I don't know - and in most cases, it's not feasible to attempt to determine that - the producer needs to test remaining animals in an attempt to identify and remove any other PI animals in the group.

Thanks. Lucky_P, you are the go to guy when details are wanted. I was reading the OP as meaning the heifer had tested positive for BVD and PI (parainfluenza). While waiting for your response, I was doing some googling research and found the reference to Persistently Infected. I then went back to the thread and realized that is what was confusing me. When I used IP, that was a typo for PI. Knowing the method is testing for the antigen explains a lot. I assumed those tests that look for the antibody titers would give positive results if the subject had been vaccinated with an MLV vaccine. But how does the antigen test distinguish between a natural virus and the MLV virus in tissue or serum? I am thinking those MLV virues in the vaccine could be found but I assume they are not because there would be too few to show up. Is that the way it works?

 

[Dave]

Thanks Lucky P for the explanation. That is pretty much what my vet said. I wasn't to concerned about the modified live being the issue because the other 14 that got vaccinated on the same day all tested negative. The other heifers are all out to pasture and will be moving about 7 miles away in a couple weeks. They wont be back home until October. I am figuring by early August the PI heifer will be in the freezer. I didn't figure that the virus would be long lived but had been unable to find out and answer to that question. The only other cattle that will be on the place during the summer are the teenage pregnancy heifers and they will be several hundred yards from the pen that PI is in.

The nieghbors escapee turns out to be a steer. A very ugly low line angus steer. He looks like an inbred runt to me. It turns out he is a regular escape artist and traveler. Last week he got hit by a car and the owner gets to pay a couple hundred for the damages to the car. This is just the first time he has made it all the way to my place. He has a date with the butcher too.

 

[Lucky_P]

inyati,
The Ag-capture ELISA does not distinguish between vaccine virus and 'field' strain virus. Unlikely that vaccinated animals would test positive, but the manufacturer of at least one assay gives that caution.
An acute infection with field strain could certainly cause a positive Ag-capture or IHC result - back in the day when immunohistochemistry was the go-to test for PIs, my buddy at UofWY looked at thousands of 'em - and said you could not differentiate between a PI and a known acute infection - viral antigen was everywhere with both. Don't believe I ever discussed viral presence in skin of vaccinates with him, though.

You should get antibody titers in animals vaccinated with either MLV or inactivated viral vaccines - I doubt that the manufacturer would go forward with challenge studies if there were not measurable titers; don't know (I haven't looked) at what level, if any has been determined, that antibody titers are presumed to be protective.
With the advent of Ag-capture and PCR technology, we rarely do BVD titers here anymore - and almost never a single-sample titer(need that 'convalescent' sample 2-3 weeks later to see if titer is increasing/decreasing/stable for a titer to really mean anything.)

 

[inyati13]

Thanks, Lucky_P. Dave, I hope I didn't take your thread off track and good luck on the heifer.

 

[greybeard]

Thanks, Lucky_P. Dave, I hope I didn't take your thread off track

I'm glad you did--more good info got posted because of it.