Testing Goats for CAE, CL, and Johnes

Episode 88
For the Love of Goats

Testing Goats for CAE, CL, and Johnes featured image

Whole herd biosecurity screening is a valuable tool that we can use to feel confident that we have a healthy herd. Washington State University has a biosecurity screening test that uses one tube of blood from a goat to run tests for caprine arthritis encephalitis (CAE), caseous lymphadenitis (CL), and Johnes.

In this episode, we are talking to Dr. Claire Burbick, Associate Professor at Washington State University and a faculty member of Washington Animal Disease Diagnostic Laboratory.

CAE, CL, and Johnes are all highly contagious, so if you bring in a new goat and don’t test, you could wind up with multiple goats testing positive in a few years.

Dr. Burbick goes into detail about how each test works, how accurate they are, and next steps if you get a positive result.

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Introduction 0:03
For the love of goats! We are talking about everything goat. Whether you’re a goat owner, a breeder, or just a fan of these wonderful creatures, we’ve got you covered. And now, here is Deborah Niemann.

Deborah Niemann 0:19
Hello, everyone, and welcome to today’s episode. I am really excited about bringing this episode to you today, because we are going to be talking about biosecurity screening that is available from Washington’s Animal Disease Diagnostic Laboratory at Washington State University. And, we are joined today by a faculty member of that lab, Dr. Claire Burbick, an associate professor at Washington State. Welcome to the show today, Dr. Burbick,

Claire Burbick 0:46
Thank you so much. It’s really a pleasure to be here.

Deborah Niemann 0:50
So, I have had goats since 2002. And I’m really grateful that I got started with people who took biosecurity very seriously, especially in terms of CAE. And so, right off the bat, the first person I bought my goats from had a herd that was tested negative for CAE. And she told me about Washington State’s Diagnostic Lab, and that’s where I needed to continue to do annual testing of my goats. And, I’m so grateful for that. Because, when I was building my herd from 2002 to 2005, we actually bought two does from herds that were supposed to be clean that came back positive for CAE. One turned out to be a false positive, and the other one did have CAE. We went through and did a PCR to confirm that. And so, I wound up selling her to someone with full disclosure, and the person was going to keep her and a wether as pets. Had I not done that, who knows how many years down the road I would have been with a herd full of goats that were positive for CAE.

Deborah Niemann 1:56
So today, I wanted to talk to Dr. Burbick about the biosecurity screening and why it’s so important. And of course, online, you can find people who disagree with everything, and I also want to talk about some of those misconceptions that are out there that people have about testing and things like that. So, right off the bat, let’s just start with: I love the fact that, like, today—and I think it’s been, like, at least 10 years, maybe longer—that Washington State has had the biosecurity screen, which means one tube of blood, 3 CCs, or three mil of blood is all that’s needed. And, they can run CAE, CL, and Johne’s test all on that one tube of blood. Can you talk a little bit first about how the testing works? And what the tests are, like ELISA? And that kind of stuff?

Claire Burbick 2:50
Yeah, sure. So yeah, we actually, you know, request 3 to 5 CCs of blood to be able to really do all the testing that’s needed. Plus, if anything has to be retested, or additional tests are requested from, you know, the submitter, that we don’t have to, you know, keep going, “Oh, but we need a little bit more… We need a little bit more…” So usually, when we get that 3 to 5 mil or CC, we can really do everything and then some for the testing needs of the submitter.

Claire Burbick 3:20
And so, yeah, Dr. Everman, who has since retired, was at the lab for, oh my gosh, 40-plus years. And, he was really instrumental in putting together kind of all of the small ruminant testing and kind of outreach that model is known for. We also… Kind of just for historical perspective, Washington State University was the place where the CAE ELISA was developed. And I believe that was in the late 70s. And so, we’ve really been working in small ruminants for a while. And, you know, I’ve kind of tried to be of service there, because, I know, you know, there’s not a huge amount of attention to small ruminant medicine and testing, unfortunately, despite, you know, a lot of folks having sheep and goats. And so, there’s there’s definitely some need there, and we’ve tried to to facilitate that as we can over the last years.

Claire Burbick 4:15
But, for our kind of standard biosecurity screen for herds, we have ELISA for CAE and Johne’s disease, and then we have a special CL test, which is the synergistic hemolysin inhibition test. So, it’s a little bit of a mouthful. It originally was developed at UC Davis for horses that had kind of the horse version of CL, but it was kind of reused shortly thereafter to be able to look at antibody responses in sheep and goats. So, it’s an interesting test. It involves culture and bacteria and toxins and seras. It’s a very fiddly test, I would say, but it’s what has been fairly reliable for us as far as CL antibody detection goes.

Deborah Niemann 5:05
Okay. Let’s go ahead and start with the CAE test then, because that was the original one that I knew was really important to test for back then in 2002. And then, everybody was saying that, like, basically, if it wasn’t an ELISA, it wasn’t really that reliable, because the AGID had a pretty high level of false negatives. So it was like, “Well, you got a negative on a AGID, but it could be a false negative,” which is, like, worse than not knowing anything. So, can you talk about the difference between the ELISA and the AGID?

Claire Burbick 5:44
Yeah. So, the AGID is what we would consider a less sensitive test. And so, that’s why we might miss animals that have antibodies present. And so, the AGID is actually… It’s an agar-based test. So, we actually use part of, you know, viral protein, that kind of migrates through a agar plate with sera that migrates also, and where they meet, they precipitate out if there is an antigen-antibody complex, basically. So, it’s—and I don’t want this to come out the wrong way. But, it’s kind of an old-school test. It’s one of our, you know, first immunology assays before there were, you know, widespread use of ELISAs. And so, as people have advanced in diagnostic medicine and brought ELISAs on board, we really are able to increase our ability to detect antibody just with the platform of how the ELISA works, and how it signals, and how we read it. And so, those tests tend to be more sensitive.

Claire Burbick 6:48
Sometimes the AG ID can be more specific. And so, there are situations where we will use that—not for CAE, but for other viral diseases that we might use it in combination with an ELISA. But, the ELISA is a much less subjective test; it’s high throughput for us. And, it just is a… kind of a better test all the way around.

Deborah Niemann 7:10
And is the accuracy for the ELISA, like, 99%?

Claire Burbick 7:14
Ah, so this is where we get into the difficulty with these tests. So, we do have sensitivity specificity that’s really good for the CAE ELISA. It’s slightly better for goats than it is for sheep. The only problem with just looking at the sensitivity specificity of these tests, is that it really doesn’t tell you the whole story. So really, it’s part of a database that includes the prevalence, or expected or estimated prevalence, of infection to give you a positive and negative predictive value. So, we know that the test is very good. However, when we put a test that’s very good into a certain level of prevalence of disease or infection in the population, it actually changes the interpretation somewhat. So, we know that if we have a lot of infection, we’re going to be really confident in the positives. But, we’re not going to be as confident in the negatives, because we know that we have a lot of infection. And it’s vice versa. So, we know in a low-prevalence situation where we don’t have very much infection, we know we’ll be more confident in those negative results, and maybe less confident in those positives. So, we might see more false positives in that situation.

Claire Burbick 8:35
So, even though the test has its own kind of intrinsic value, it really has to be interpreted in light of the herd prevalence, herd health, you know, kind of the database that goes along with that herd of origin—or the herd of origin’s origin. Sometimes we need to go back and say, “Where did you get this animal from? And what’s their testing history? And what’s their disease history,” like, so that we can fully understand and interpret those results. So, it gets really, really complicated. And those are conversations that I have a lot with people, when they’re like, “Man, this test result doesn’t make sense. I’ve never had this issue before. I have a closed herd. Why is this positive?” You know, and then we can kind of walk through maybe some more refined interpretation.

Deborah Niemann 9:25
I’m so glad that you explained all of that. Because, that is really… It’s a good backdrop for explaining, like, what happened to us when we got the false positive. Because, we were testing annually when we were building the herd, and it was a goat that we had had for about 2 or 3 years already. She had raised kids here, and I had even used her milk to feed bottle babies. And, she’s the only one who came back positive. And we were like, “Oh my gosh, this isn’t possible.” Because her daughters tested negative, and the kids who had gotten her unpasteurized milk in a bottle were negative. And so, I called Washington State and talked to probably whoever your predecessor was. And they said, “Oh, I’m so glad you called. You’re right. This doesn’t sound like the goat is really positive. So, we should do follow-up testing.” Is that still the way that you would do things now?

Claire Burbick 10:20
Yeah. I mean, I think that’s one thing that’s always an easy second look, to see, “Is this a consistent finding?” Because sometimes it’s not. And that can be very helpful. But sometimes it can be, but still be a false positive. So, it’s not super straightforward. A lot of times retesting is where we start, and then we kind of see where we get from there, and maybe try and dig into, you know, “Was there some possibility of exposure?”

Claire Burbick 10:51
I think, you know, when we start talking about some of these things, we get into this little bit of discussion about the disease itself. And som sometimes people can be very, very surprised at having a positive animal. You know, and they’ve even tested it before, and it’s been negative. But, one of the things that can happen with CAE, which is a little bit harder to nail down sometimes, is you can have animals that become positive multiple years after they’ve been infected. So, it’s a little bit of a delayed zero conversion. And that has been reported. And so, that can make things a little bit complicated, too. So, it’s good to have discussions about this, and kind of talk through all of the possibilities and exposures and history of that animal, to kind of see where you’re at with interpreting the test. But, it can get really complicated just also based on the nature of the particular disease that we’re trying to assess, whether it be CAE or Johne’s or CL. There’s always a little bit of discussion that needs to happen about the pathogenesis, or the trajectory of the disease, and some of the things that can be very unhelpful about trying to detect, you know, whether animals are positive or negative in some of those particular infections,

Deborah Niemann 12:09
Right. I’m glad you mentioned the information about how it can take a while for an animal to zero convert. Because that was one of the things, too, that we talked about, you know, when I called in, like 17-18 years ago, was the fact that, like, you know, testing that goat’s kids that were still nursing would not really give us any good information. Can you talk a little bit about testing kids? Like, when would be the first time that you should test a kid, and how accurate those results would be?

Claire Burbick 12:42
Yeah. So, we do recommend, if we’re trying to really assess that individual animal and their status, kind of just in general to test them when they’re 6 months of age or older. Just because that’s when most of the maternal antibody that they’ve gotten through colostrum is waning, because we want them to get, you know, beautiful antibodies from, you know, the doe, or the ewe, so that they can obviously be protected from disease. But unfortunately, we can actually pick those maternal antibodies up on our antibody tests, because they are circulating in the blood. And so, that’s why we recommend 6 months or older.

Claire Burbick 13:20
It gets to be a little bit tricky with Johne’s, because a lot of times, we’re not going to be able to detect an antibody response for quite a while past the 6 months recommendation. So, a lot of Johne’s recommendations, you know, is to start testing them at 18 months to be able to have a better chance of picking up antibody.

Deborah Niemann 13:43
Okay. So, with CAE, if a doe has CAE, and her kids have been nursing, are those kids more likely to show a false negative or a false positive? Or is it not predictable?

Claire Burbick 13:57
It kind of depends a little bit on, you know, on dose, and just the genetics of those animals. So, it’s possible that, you know, if she doesn’t have a lot of antibody, she might not pass it to them. So, it could be that they test negative even though they’ve been exposed; it could be a delay in when we start seeing their own antibody; but I haven’t seen anything in the literature that really gives a good assessment. And in those terms, I would say, probably the majority of animals that have been infected will test positive by 6 months, but there certainly could be a proportion that are delayed or that don’t get infected at all.

Deborah Niemann 14:40
Okay. One question that I get quite a bit is that people say, “Well, the doe has CAE, and the milk has antibodies in it, then why doesn’t that protect the kid?”

Claire Burbick 14:49
Yeah. ‘Cause the antibodies aren’t protective, is kind of the gist of it. So, we have a whole slew of antibodies that, you know, do different thing. So, some are neutralizing, you know, and some are not. Some act in different ways. And so, just because you have antibodies doesn’t mean it actually helps protect you from infectio; it just means you’ve had an exposure to that virus and have mounted an antibody response that’s detectable. So unfortunately, you know, for this virus, a lot of what we need is not an antibody response, but is more cell-mediated—so a different branch of the immune system—to help with that. And so, yeah, just having antibody by itself doesn’t mean that it’s actually, you know, binding up the virus in a way that keeps it from being passed on.

Deborah Niemann 15:38
Okay. So, is there anything else that people need to know about this CAE test that I haven’t asked yet?

Claire Burbick 15:46
Not, I would say, in particular for that test. But, I would say, kind of my biggest hand-wave is to really think: So you’re testing your animals. Try and plan. Try and come up with a plan. What if somebody’s positive? Because, I think those are the biggest questions that I have coming in, is just people are like, “Oh, my gosh,” you know, “what do I do now?” And so, it’s kind of good when you’re going to start doing biosecurity testing is to try and run through the exercise—which I’m sure will be very painful for everybody to do. But just to say, “Okay, I’m hoping for negative, but what’s my plan if something does come up positive?” So that you can kind of think through, you know, what next steps would be. You know, maybe you need to quarantine that animal for a while, while you figure things out. You know, kind of, what are the goals of your farm? You know, is it okay for you to have positive animals? Like you said, you were able to have, you know, your one CAE-positive goat to go to someone who just wanted a companion. So, it really wasn’t as big of a concern in that situation, as it would be if you are producing, you know, brood stock or something like that. So, just to try and kind of think through the contingencies of, “Maybe I will get some unexpected results, things that I don’t want, but what do I do at that point?” Because, I think those are really important things to kind of work through before you you start doing testing.

Deborah Niemann 17:14
Yeah, exactly. And that’s one of the reasons I’m such a big proponent of people doing testing as they’re building their herd. Because, it was so much easier for us. You know, like, the goat that tested positive, she had only been here for a couple months. And so, it really was not that big a deal. You know, it’s like, “Oh, she’s positive. Okay, she never kidded here. She did not nurse kids.” So, it was just her. And we had only had her for a couple months; we were not attached to her. Like, if we had not done testing, and we had waited, like, years, until all of a sudden, you know, we saw swollen knees or, you know, lots of cases of mastitis, or other symptoms of CAE, we could have been looking at, like, half of our herd at that point. And, you know, goats that were born here that we were very attached to, that we were very fond of, and then it would have felt devastating to think, “Oh, my gosh, what are we going to do with these goats?”

Claire Burbick 18:11
Yeah. And those are… I’ve had some pretty awful conversations with people who are in that exact situation. Because, you know, a lot of folks, these are definitely part of, you know, a business, but also more than that, I would say, for a lot of folks that I talked with. And so, it’s a really agonizing process to go through. And I think, you know, having a little bit of pre-planning, so it’s not, you know, just a shock, and then you have to figure out what to do, would be great.

Claire Burbick 18:41
And also, my other second hand-waving thing is to really try and develop as much as possible, you know, a relationship with a veterinarian to kind of also help look at the premise, you know, look at nutrition, look at bigger stuff, look at parasites, control, all these things. You know, really have someone that you can touch base with, because when people call us, we can certainly talk through test interpretation. But there’s so much more to keeping healthy animals, into doing biosecurity, than just these handful of diseases. So. And then us, we can also confer with veterinarians about, you know, test interpretation in light of their understanding of your management and your goals and things like that. So, those are kind of my big picture suggestions as far as, you know, maintaining optimal herd health and biosecurity.

Deborah Niemann 19:33
So, back 17 or 18 years ago, when we had the goat with the false positive, what we ultimately wound up doing was a PCR test on her, as well as every goat that had ever consumed her milk in the last couple of years. And, they all came back negative. And at that time, I think Colorado State was the only place that did the PCR. Is that a good follow up if you get a positive today?

Claire Burbick 19:59
So CAE, the lentiviruses are a little bit tricky. So, they have an uncanny ability to hide out in different cells and different areas, and also to mutate quite a lot. And so, using PCR, we use really specific primers to target, you know, those viruses. And so, sometimes those primers aren’t going to necessarily pick up, or the virus might be in a different sample than what we’re getting. And so, you can miss it. And so, that’s why it hasn’t been a super widespread adoption of the test, just because we can have some issues there. But, it is a good thing to do, but I think just with the understanding that there can be some issues with that test as well, just because of the nature of that virus.

Deborah Niemann 20:50
Okay. All right.

Claire Burbick 20:52
Yeah, nothing in diagnostics is never clear cut, unfortunately.

Deborah Niemann 20:57
Right? Yeah. And a big part of us deciding that that it was a false positive was the fact that, like, every goat… Like, I think there were four or five other goats that we tested that had all consumed her milk, and that were, like, a year or two old, so like, all of them also tested negative on both the ELISA and the PCR. And so, we were, like, talking to multiple people. It was like, “Okay, I think this is about as sure as we can get.” And, as it turned out, that goat lived to be 16 years old and was as healthy as could be for, you know, the rest of her life. So, she was clearly did not have any diseases.

Claire Burbick 21:36
Yeah. And I think that’s really important. Because, I mean, not everyone would go to those lengths for a particular animal. Some people are like, “I just don’t want to deal with it.” But I think, you know, you can build up a database of information to give you that confidence that, you know, the testing was not reflective of what the status of the animal was. And so, you know, it takes a bit of effort—like, pretty incredible effort on your part, I would say—but it is something that, you know, we can definitely build towards, especially when you’re looking at the animals and they’re healthy; they’re healthy when they’re older; you know, animals that have been exposed are continuing to be negative. Those things really help. You know, it’s just some people aren’t as patient as you. That’s very, very admirable.

Deborah Niemann 22:25
Well, she was a favorite already at that point. I think she was, like, the fifth goat we ever—and, as it turns out now, at least a third of the goats out there, like, came down from her. So, she turned out to be fabulous. So, I’m really glad that we did go to that trouble, because I mean, her genetics were quite amazing. I felt really lucky that I was able to buy her when I did.

Claire Burbick 22:50
Yeah. Although, I guess I would also say that, you know, we’ve had conversations to where people, like, you said, they have an animal with really valuable genetics that is truly positive. And you can manage, you know, those animals to reduce the likelihood of transmission, as well as just, you know, again, having to manage that biosecurity in mind. You know, some people do have the facilities to do stuff like that, and the manpower and the time, so even having a positive animal, you know, you can work towards safely managing that animal. And that’s something that people do, as well.

Deborah Niemann 23:28
Exactly, that is a really good point. Also, let’s go ahead and move on to the Johne’s, then, since it’s also an ELISA test.

Deborah Niemann 23:36
Johne’s, it’s funny. I remember initially, I don’t think I heard about it for 2 or 3 years after I got goats. And then, one day, my mentor said to me, “You know, people worry so much about CAE. What they should really be scared of is Johne’s.” And then she explained to me why, because it can live on the pasture for, like, years and stuff, because it’s transmitted through fecal pellets. So, can you talk a little bit about the Johne’s test? On an individual goat basis, it is not as accurate as the CAE test. So, can you talk about the accuracy of the Johne’s test?

Claire Burbick 24:10
Yeah. So, Johne’s is really… I think, if I had to pick my least favorite disease, it would be Johne’s. Just because it’s so difficult to diagnose before animals actually get sick. And, it takes a long time for them to get sick. So, you have an animal that looks healthy and normal, that’s shedding the bacteria into the environment, which is not great. This is, like, the worst case scenario ever.

Claire Burbick 24:37
So, for Johne’s, the ELISA is interesting. So, it definitely has different sensitivity specificity than the CAE test. So, for clinically normal animals that are early in their infection—which could be, you know, animals that are 18 months and older potentially—it definitely is going to have a lot more false negatives than the CAE. So it’s more prone, just inherently in the test, to not picking up animals very well until they get to be clinically affected, and then it works really well. So. Which doesn’t help, in that, when you’re trying to figure out, you know, if you have infection on your premise or not. So, that’s one of the big problems with both the ELISA and also the PCR on feces, is that the animal has to get to a level in progression of their infection, where we can start picking up an immune response and shedding. And that can take a long time. And so, that’s really where a challenge in the diagnostics is, is there’s just not a great early detection test for those animals. And so, that’s why the cycle of infection can be really difficult to break, is because you have animal shedding, and they look perfectly healthy, and sometimes very difficult to pick it up with the test that we have.

Deborah Niemann 26:04
Okay. Because of the biosecurity screen is all done with one tube of blood, but you also mentioned the fecal test, can you talk about the difference between the blood test and the fecal test?

Claire Burbick 26:16
Yeah. So, the blood test is looking for an immune response to that bacteria, to the mycobacterium, whereas the fecal test is actually looking for the bacteria. So, it would be what we will call a more “definitive” diagnosis, because we’re actually picking up bits and pieces of the bacteria that’s being shed into the intestinal tract.

Deborah Niemann 26:39
So, will a goat test positive on the fecal test earlier than on the blood test? Or does it vary?

Claire Burbick 26:47
So unfortunately, it can vary. So, we can pick up shedding before an immune response, and we can pick up an immune response before shedding, which makes… Sometimes, you know, when people are like, “I have, you know, positive ELISA result but a negative PCR, what does that mean?” And that can be a little bit complicated, just based on the timing, and how the immune response is sort of waxing and waning depending on where they are in their infection. And so, yeah. So I think historically, you know, we’ve kind of said, “Do the ELISA first, and then follow up with PCR.”

Claire Burbick 27:24
My opinion on this—and I’m sure people can argue with me about it—is to do both, and try and hedge your bets and see, you know, where you can pick up any positives. Because it can be variable, depending on the animal and the dose, and you know, how long they’ve been infected. And so, I personally recommend doing both. But, just because I think it gives you, you know, a better shot at figuring out what’s going on.

Deborah Niemann 27:49
Okay. It sounds like doing both of them would be, like, a really good idea for somebody who’s building their herd, to make sure that you have all negative animals. And then, maybe after a number of years of getting, like, all negatives, then you could just stick with the blood maybe?

Claire Burbick 28:05
Yeah. And I think there’s a lot of different ways that you can screen, you know, once you have a baseline of what’s going on, and you know what your risks for introduction are if you’re, you know, bringing new animals in, or, you know, traveling around and having a lot of exposures there. But yeah, I think you can start kind of tailoring it back. Some diagnostic labs have pooled fecal testing. So, that can be a great approach as well. We don’t for small ruminants, here at WADDL, but other places might have that available. So that’s, you know, another thing to consider, is maybe there’s some opportunities to pool fecal samples to get at that question, too.

Deborah Niemann 28:44
One of the things that scares me is that a lot of times, you know, people have mixed farms, and somebody may be buying goats from a farm that has cows. And Johne’s… Actually, the incidence of it in cows, when I see numbers, that like, it just looks horrifying to me. Like, the estimates on the percentage of cows that are positive for Johne’s. I don’t know anything about the cattle industry. I do know we got a cow one time from a dairy, and they did test for Johne’s—which is why I felt comfortable getting a cow for them, because they had all negative tests. Other than that… Because a lot of times, you’re just getting a cow from, like, another backyard homesteader who doesn’t do that. Are there any other, like, special concerns about getting goats from people who have cattle? Other than asking them, like, “Have you tested your cows also for Johne’s?”

Claire Burbick 29:39
Yeah. I mean, I think if there’s other livestock on the premise—and a lot of people do have kind of mixed-animal farms—is that yeah, I would definitely, you know, recommend, “What’s the herd status? What’s the testing history?” You know, “What illnesses have been…?” You know, “Did you see salmonella on the farm?” You know, because there’s a lot out there that could potentially, you know, be passed around. Maybe not so much on the parasite side, but certainly the, you know, bacteria would be something that might be a little bit more of concern. But I would say that, you know, probably for Johne’s, I would try and make sure that you know the status of the cattle as best as possible, too.

Deborah Niemann 30:20

Claire Burbick 30:20
Or, if there was a lot of intermingling or, you know, if they kept them completely separate and were herd biosecurity aware, I guess that would be, you know, another thing to consider. But I would say, yeah, there’s definitely things that, you know, can cross species, and Johne’s would be one that I would ask about.

Deborah Niemann 30:37
Right. And this slides right into my discussion on CL. Because, last week, in the episode with Dr. Pesato where we talked about CL, specifically I mentioned someone that I had been talking to who had had goats for four years, and all of a sudden she had abscesses popping up on the goats. And then, she decided to do CL testing, and found out that a lot of her goats were positive for CL. And, she could not figure out how that happened. Because, all the goats came from herds that were supposed to be CL-free. But then, in talking with her, I discovered she also had sheep on her farm. And she had no idea what the CL status of the sheep was. So, I mentioned that. Like, because CL also can be in sheep.

Deborah Niemann 31:24
So, let’s talk a little bit about the CL tests now. You said it’s different. The blood test for CAE and Johne’s is an ELISA. But the CL test is going to be different.

Claire Burbick 31:36
Mm-hmm. Yeah. So, the CL test… I mean, again, it’s detecting antibody, you know, like what the CAE and Johne’s ELISA. But I think this is a good time to bring it up. So, a lot of these ELISAs and these serologic tests are really kind of giving you a more confident, like, herd-level understanding of what’s going on. Sort of a surveillance of level of infection. And again, having a look at, you know, how confident you are based on understanding that herd health history and previous testing history, because having positive or negatives or titers, you know, still has to be taken into account what’s going on, you know, with this other information that you use to interpret those tests.

Claire Burbick 32:24
So, for CL it gets to be a little bit tricky with the serology. I really discourage people from using the serology as a guide for diagnosis of CL. I really encourage people to do culture if they’re seeing abscesses. For two issues. One, a titer doesn’t mean that the abscess is CL, because goats… I don’t know what they’re doing out there, but they love getting abscesses in places that look like CL, and it’s not CL. So, when I look back at our data—because we do a ton of cultures for CL from across the country—we get, you know, I would say maybe 50% to 60% are not CL. But they’re in classic CL places and freaks everybody out really badly. And so, the other issue that we have is that we’ll culture. We’ll get, you know, corynebacterium pseudotuberculosis—the cause of CL—and they’ll have a negative CL titer. So, we do see that as well, which can be misleading.

Claire Burbick 33:26
So, I think when we have an abscess on an animal that can be sampled, I say “Treat it like CL, but prove it otherwise.” Because a lot of times, it’s something else. Some other bacteria that got poked into something. You know, they got an abrasion. They have a wound in the mouth. They have a little, maybe, a little dental disease or something. And that’s, you know, really just a one-off incidental issue, not a herd health concern. So, really with the CL, when I talk to people about doing interpretation of those tests, I say, okay, you know, you do your herd, you do your proportion of animals, and you can look at it and say, you know, “All of my animals have titers, so I’m concerned that there’s CL in my herd. I can’t pick out, you know, who all is going to be affected, but I know that I need to keep an eye on my animals.” Or, “I have almost no titers, or maybe I have one animal with a low titer. You know, I haven’t seen abscesses coming on my animals.” So it’s kind of, I’m not as confident in using that particular test as an individual animal diagnostic test, versus you have an abscess and you culture that and you can say, “Yes, we have the bacteria,” or “No, we don’t.”

Deborah Niemann 34:40
Right, exactly. Then, that actually is so funny, what you said about them getting an injury in a place that’s, like, perfect for CL. Because that happened to me two years ago. My husband comes, he like shows me this picture, and I’m like… Yes, “panic-inducing” is the perfect way to describe it. I was freaking out. And I had a vet out here, like within, like that afternoon, getting the culture to send it to you guys. And it came back that it was normal skin bacteria. So, it’s like, how did she manage to poke herself right there under her jaw, like, where a CL abscess would have been? Like, if she could have just poked herself somewhere else.

Claire Burbick 35:22
Yeah. Unfortunately, we have also had very nontraditional places where abscesses have developed that have been CL, as well. Which is, you know, when I look at all of, you know, our accessions that come in and say, “Oh,” you know, “this was, like, along the spine,” or, you know, “is on a hind leg,” or something on the side of the animal. So definitely, even if it’s in, you know, a very weird area, it can still be CL. So, it’s kind of both sides, where it’s like, “Gosh, that doesn’t look like a place where CL would be,” it could still be CL. Or, “Oh, that’s totally CL. It looks like it; it’s got the right consistency.” Which is another thing that people ask about is, you know, “This abscess doesn’t look like CL. It’s very liquidy. It’s very, you know, whatever.” But, it still could be CL.

Claire Burbick 36:11
So unfortunately, bacteria will not read the book, will not cooperate, will not do what we want. Sometimes they do, but that’s when we celebrate. We’re like, “It actually read the book and did what it was supposed to do!” But otherwise, I think I would caution, you know, just assuming if you see a goat with an abscess that looks like it could be CL, to treat it like it’s CL, as a confirmation. Because a lot of times it turns out to be something else. So, I really advocate for people to culture those abscesses to confirm.

Deborah Niemann 36:43
Yeah, absolutely. And it makes so much sense when you say that it really could be anywhere on the body. Because, when you think of the fact that internal abscesses for CL can be anywhere in the body, why not on the outside of the body? So.

Claire Burbick 36:56
Yeah, yeah. And we don’t see a ton of internal abscesses with our goats—more with the sheep. And I think it’s based on, you know, kind of management practices and things like that. But yeah, it definitely, unfortunately, can be anywhere.

Deborah Niemann 37:13
One of the things I think is really important—because some people might be listening to this and thinking, “Well, if these tests aren’t 100%, why should I do them?” And you’ve touched on this, and I just want to make sure that everybody understands, that this is not a one-and-done thing. You don’t just do one test and say, “Oh, we’re all good.” Or, “It’s bad, we should cull every animal that’s got a positive.” It’s like, this is a screening. It’s biosecurity screening. And it’s something that you do year after year, and that’s where that confidence level gets built up.

Deborah Niemann 37:44
You know, we started testing, like, after we had our goats for a year, and so it’s been 19 years. All negative tests for the last 17 years. And, like, that’s a huge level of confidence there, to have no positive animals for 17 years. So, I sleep really well at night knowing that.

Claire Burbick 38:05
Yeah. And I definitely don’t want to downplay the use of these tests. But I think, like you said, people are like, “Well, this is my, you know, black-and-white answer right here.” And unfortunately, it doesn’t work that way. You really have to have that holistic view of management, basically. So, what good is a negative test when your animals have mineral deficiencies, you know? Or have issues with parasites? So, you know, it’s really just part of that whole herd health, like, compendium that you have, where you are recording, you know, like, what their feed is, and what their feed needs are. You know, maybe do trace minerals on occasion. Or, if animals start looking like, you know, they have hair coat issues, do fecal floats. Make sure that, you know, you understand parasite loads, and you know what other issues that could be, you know, kind of regionally important. You know, do you have flukes that you have to worry about? Do you have, like, selenium issues or something like that?

Claire Burbick 39:06
So, it’s really just… It’s one part of, you know, having a good, healthy herd. But, you can’t just use it in isolation and say, “Oh, yeah, we’re done. We’re good.” Because it really is something that has to be in light of all the other things that are going on. And also over time, like you said, you know, having that many years of understanding of the status of your animals is incredible. So, just to be able to say, “Yeah, we have a really high level of confidence in the health of our animals.” You know, “This is our record of that.” And that’s, you know, really, really critical in, you know, keeping animals healthy, and also helping other people keep their animals healthy. Because, you know, we say, “Don’t buy problems.” And so, that’s really also kind of the community of people who are producing these goats that are really contributing to the health of the whole overall community.

Deborah Niemann 40:01
Yeah. You made a lot of really great points there. And I hope everybody listens to this whole episode a couple times, to make sure that you don’t miss anything, because there’s just so much good information here. And one more thing, too: that if you raise goats for long enough, at some point, you are going to have somebody contact you and say, “Hey, I bought this goat from somebody who bought it from you. And this goat is positive for this disease.” And it feels wonderful to be able to pull out your paperwork and say, “Well, her mother and her sister and her aunt and her grandmother and all these goats, you know, tested negative. So, if she has that disease, she picked it up at some point in the last 5 or 6 years after she left here.” But, you know, “It did not come from here.” Because we have no control over where our animals go after we sell them.

Claire Burbick 40:56
Right. Yeah. And I think one of the things that’s great, too, is having people who have, you know, this much experience with testing and managing diseases that, you know, there’s a lot of people I talk to who are, like, brand-new into getting into goats. And so, they’re really trying to get, you know, like, “What? How do I do this testing?” And a lot of times, unfortunately, they’re learning a bit trial by fire, because they have gotten animals that are positive for something, and then they’re just mortified and trying to figure out how to deal with that. So yeah, I think the more information that’s out there to support those folks, too, the better. You know, with having good mentorship and things like that. Because, there’s a lot of really passionate goat people out there, I have learned. I’ve had a lot of conversations over the years. And it just… Yeah, it’s pretty impressive how passionate folks are about their goats.

Deborah Niemann 41:45
Yeah, exactly. Well, thank you so much for joining us today! Is there anything else you want to make sure people know about the biosecurity screen or any of these tests before we sign off?

Claire Burbick 41:57
You know, I think it’s just, if you have questions, certainly, you know, we’re available at WADDL to answer test questions. But, you know, really, I think, just kind of think through what you’re trying to do with this information, and what your goals are for your animals, and really try and find a veterinarian in the area that you can work with that can help with some of the other herd health management-type issues. But yeah, as far as the tests go, happy to answer more questions for folks in the future. But yeah, I think we covered everything pretty well.

Deborah Niemann 42:28
All right, great! Thank you so much for joining us today. I think this is gonna be really helpful for people.

Claire Burbick 42:32
No problem. Yeah, anytime.

Deborah Niemann 42:36
And that’s it for today’s show. If you haven’t already done so, be sure to hit the “subscribe” button so that you don’t miss any episodes. To see show notes, you can always visit ForTheLoveOfGoats.com, and you can follow us on Facebook at Facebook.com/LoveGoatsPodcast. See you again next time. Bye for now!

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2 thoughts on “Testing Goats for CAE, CL, and Johnes”

  1. I have also through experience with buying goats( I only buy my baby buck for herd sires )that if the dam was cae tested DURING PREG. that the test can also be a FALSE NEG. due to the hormone levels. Also a nursing doe. Data on this please…. I ALWAYS tested my girls BEFORE breeding so as not to interfere with the results… But the baby buck I buy will be isolated and tested at 6 mo and every 6 mo until 2 yrs BEFORE he breeds my girls.

    • Hi Kat
      Did you read about these testing parameters for pregnancy and lactation in a published study, or did someone just tell you that?
      I’ve been testing my goats for years, and I’ve never seen a recommendation from a lab or been told by a vet that blood should not be submitted during pregnancy/lactation. That would basically omit the majority of dairy goats from testing.
      Also- Dr Burbick talked quite a bit about parameters for testing, and did not mention anything about pregnant/lactation impacting the results.


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