The different faces of oedema disease in pigs

In this episode, APHA's Pig Expert Group lead Claire Scott, histopathologist Toby Floyd and Veterinary Investigation Officer Ed Fullick discuss two cases of oedema disease in pigs, with different clinical presentations. Oedema disease is caused by Shiga toxin-producing strains of Escherichia coli, or STECs for short. 

Please note that this podcast includes pathological descriptions of animal disease which some listeners may find upsetting. 

This episode was recorded in July 2026.

Useful links: 

1. The case of cerebrospinal angiopathy was also described, with a picture, in the disease surveillance in England and Wales (February 2026) report which is published in the Vet Record. A case of sudden deaths and acute neurological disease due to oedema disease was described in the October 2024 report. 
2. Find out how vets can submit farm animals in England and Wales for a post-mortem examination and check if the submission is eligible for free carcase collection. 
3. Find your nearest Veterinary Investigation Centre (VIC) or surveillance pathology partner. 
4. Find out how vets can submit samples from farm animals in England and Wales for diagnostic submissions. 
5. Find out how to report suspect notifiable animal disease. 

 © Crown copyright 2026

Transcript

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SPEAKER_00 0:01

Hello and welcome to the fifth podcast in this series where we talk all about animal diagnostic investigations completed here at the Animal and Plant Health Agency. I'm Claire and I lead APHA's Pig Expert Group. Today I have Toby and Ed with me to talk about two cases of disease in growing pigs, both caused by the same pathogen, but different presentations, which we're going to unpick today. Now I'm really excited to have both of you here because it means we can tell our listeners more about how submissions move through the various diagnostic pipelines at OPHA. So before we start, Ed, can I ask you to introduce yourself to our listeners?

SPEAKER_01 0:38

Absolutely, thanks Claire. So I'm Ed, I'm a veterinary investigation officer based out of the SC Veterinary Investigation Centre. I've been here for coming up on nine years now, which uh has flown by. Um but I did have an 18-month stint down uh with Toby actually doing some histotology and work towards my FRC path part one, which I passed the other year. So yeah, some nice varied bits and pieces. It's uh it's part of the furniture now, really.

SPEAKER_00 1:07

Oh, totally. Absolutely huge congratulations on achieving your fellowship of the Royal College of Pathologists, and I think that gives just a tiny snippet of the great variety of activities that you've thrown yourself into over the last nine years. So, Ed, you were the veterinary investigation officer, so the VIO for both of these cases, and we've also got Toby along because he made their histopathological diagnosis for one of these. So, Toby, can I ask you to introduce yourself?

SPEAKER_02 1:33

Yes, thanks, Claire. Um, long time listener, first time caller. Um Yeah, I'm Toby, I'm a veterinary pathologist working at the APHA down here in Surrey. I can trump both of you by many years. I joined the VLA, as was then in 2010. I have been in pathology for about 15 years now, and I lead a small team of diagnostic pathologists providing histopathology services to our scanning surveillance program.

SPEAKER_00 2:00

Great stuff. So today is a bit different to our usual podcast because we're discussing two cases. And the reason we've chosen to do this is because these cases both have the same causative pathogen, but have different clinical manifestations and are also diagnosed differently. One of these cases was submitted from a small-scale herd, the other wasn't, but the clinical problem could have equally occurred on any sized herd. So hopefully this will be a relevant and interesting discussion for any vet seeing pigs. So let's start with our first case then. So in this case, five ten-week-old pigs had been found dead over two days. Ed, can you tell us a bit more about the history for this case?

SPEAKER_01 2:38

Yeah, this was actually from a small-scale herd of some rare breed pigs, and they've been having ongoing mortality issues in their recently weaned pigs. So on this farm, sows farrow inside in these straw-line stables, and then at weaning, which is around nine weeks on this farm, the sows are actually moved out of the stables, leaving the pigs there to be reared inside. Now, uh the pigs uh at that age are then receiving creep feed, and there were no kind of other issues really that were being reported other than these deaths in these pigs, so no sickness or abortions in any of the sows, uh, and no respiratory disease or anything being reported. Uh the herd wasn't vaccinating for anything uh at the time of submission, and the uh animals had been treated with some uh antibiotics, say some amoxicillin, uh as well as meloxicam prior to submission. Now, one thing that we we clarified with the vet with the history of sudden death was uh we asked whether there had been potentially any issues with water supplies. Now, either that's kind of issues with with cutoff or um something that we see sometimes is you know wheeling and pigs move on to different ways of drinking, that animals aren't necessarily familiar with how to access the water, but you know, these were stay had stayed in place and there'd been no no issues with water supply reported. We'd also asked whether the the vet or the farmer had seen anything in the pens that that might have potentially posed a hazard, particularly kind of wondering about toxicities. So uh they they've were really confident that there'd been nothing introduced recently that that would fit with a toxic insult.

SPEAKER_00 4:13

Great, that was super thorough, thank you, Ed. So our listeners will probably know by now that we need to ensure that neither we nor the submitting vet is suspicious of notifiable disease before we accept any animals into our post-mortem room. So can you talk me through that for this case? I guess it sounds like the epidemiological picture here in terms of deaths being isolated to one age group over a longer period of time and no other clinical signs, either in these pigs or other age groups, would have meant that you and the submitting vet weren't suspicious?

SPEAKER_01 4:43

Absolutely. I think so when we're talking about whether someone suspects notifiable disease, ultimately we'll have in our head the various notifiables that we might be concerned about. So in this time with sudden deaths, we're particularly concerned about the swine fevers. And we'll go through some of the clinical attributes and clinical um presentations that we might see with swine fever and just check, you know, are the pigs actually presenting with any red blotchiness of the skin? Have they got any rectal temperatures? And going through our clinical presentations that we might consider. And the other thing as well is looking at the epidemiology on farm. This was one particular stable of pigs that was affected, but ultimately uh there was nothing to really flag any uh anything particularly sinister that we felt warranted further investigation.

SPEAKER_00 5:28

Okay, so we'll put links in our show notes as to how vets or keepers can report suspicion of notifiable animal disease. So it was decided then that these three 10-week old pigs could be submitted to you for post-mortem examination and disease investigation at APHA Thirsk, and we'll put links in the show notes for how VETS can submit carcasses or samples to one of APHA's veterinary investigation centres or surveillance pathology partners. And this is to aid vets in diagnosing disease on the farms they work with, and also fulfil the remit of our diagnostic service, which is to detect new or re-emerging animal disease-related threats. So, Ed, tell us what you found at post-mortem examination.

SPEAKER_01 6:08

So all of the pigs that were submitted were were in fair body condition when we looked at them, with nothing particularly uh evident on the external examination. So we'll always make sure we're we're checking externally whether it's for evidence of diarrhoea or whether it's for vesicles in between feet. We just make sure we do a really thorough external exam. And there was nothing really much to see. So once we started cutting in, we found some prominence of the subcutaneous vasculature, uh a bit of tentative edema of the eyelids, and then within the body cavities, uh there was maybe an excess of serous peritoneal fluid with a few fibrin strands, which isn't the most uncommon finding, and pigs certainly always love to lay down a little bit of fibrin for us to find. So uh and and once we started getting into the gastrointestinal tract, it had feed present in the stomach, which fits with that history of sudden death. In terms of then throughout the intestinal tract, the mucosia of the distal third of the jejunum through actually continuing to the colon had a rugose and really hemorrhagic appearance with red liquid contents, and and this was quite a consistent finding across all three pigs. And then there was scant mucoid, uh kind of pink coloured feces present in the rectum. And then looking at the the uh intestine as a whole, there was this edema of the mesocolon, so that kind of connection between all the loops of the in of the large intestine were quite expanded and gelatinous appearance, uh, and then the mesenteric lymph nodes were generally quite enlarged and reddened.

SPEAKER_00 7:39

Okay, that's brilliant, thank you. So there's quite a lot going on in this carcass, and actually this case really, in that the case sounds quite a almost quite typical of a common presentation that we investigate here at APHA, which is pigs being found dead. Um, but the carcass has some more maybe unusual findings. So, Toby, can I ask you a bit about how you would problem solve cases like this and what diagnostic testing you'd want to instigate as a result of going through that problem-solving process?

SPEAKER_02 8:08

Yeah, well, we have a case of sudden death in post-winged pigs with edema, possibly of the eyelids, certainly of the mesocolon. So we're already thinking about one main differential, I think, aren't we? It's edema disease. But we also have uh seeming inflammation of the intestinal mucosa. So we might want to think about other enteric bacterial infections prevalent in this age group, like lawsonia, uh, salmonella or brachispira. So I'd probably start with aerobic culture of the small intestine contents, collect some samples for screening for other enteric pathogens and potentially any underlying viral infection like PERS or PCV2, perhaps ought to be borne in mind as well. Particularly, uh, we've got uh headnoted the enlarged mesenteric lymph nodes always makes you wonder about sourceine circoviruses.

SPEAKER_00 8:53

Okay, so when you say PERS, you're referring to porcine reproductive and respiratory syndrome, and PCV2 is porcine sarcovirus type 2, which is rare in commercial pigs now given vaccination rates, but these smallholder pigs weren't vaccinated, so PCV2 would be more of a possibility, I guess. Uh but you've talked there about how you've prioritized your aerobic bacteriology on a charcoal swab taken from the terminal small intestinal contents, because that's our sample of choice for investigating your top differential, which is edema disease, which we're going to talk about in more detail soon. But I just wanted to discuss so so you haven't talked about culturing swabs taken from systemic sites for pathogens which might cause bacterial septicemia like Streptococcus or Glacerella paraseuis, and could lead to the mortality described here. So I was wondering whether you feel that these were less likely in this case.

SPEAKER_02 9:47

Yeah, certainly, with cases of sudden deaths in pigs of many age groups, then you might wonder about septicemias. In this case, the the gross lesions really did center on the digestive tract, uh, and we've got a clear leader in terms of differentials in edema disease.

SPEAKER_01 10:03

Yeah, no, I'd agree. I would probably still consider carrying out an aerobic um culture of the uh meningial surfaces, uh your streptococcal meningitis and um or as you say, like lacerella. I'd be less likely to do culture from multiple systemic sites. I I think you've you've got a strong indication and ultimately you want to be guided by that gross pathology rather than necessarily just going through the motions of, oh, I I I've got a dead pig, I've got to do uh swabs versus septicemia. But what I would say is if if you are in doubt, and certainly in some of these cases, the edema can be really subtle, and and whether it's due to acuteness and not occurred or whether it seems to sometimes almost dissipate post-mortem. If you are in any doubt, just take some swabs and you can keep them in the fridge or or send them along to the lab and say, only culture these if you've not got anything that's that's raising uh or fitting with our suspicions of edema disease from that initial 24-hour bacteria result.

SPEAKER_02 11:06

Yeah, I was just thinking about your meningeal swab there, Ed. I think that is a good point because meningitis in pigs, I think, isn't always terribly evident grossly. Sometimes meninges are in congested, and that can be the case in pigs without meningitis as well.

SPEAKER_01 11:19

Fully agree. It's not it's not often we get a really nice, uhlant, kind of obvious change.

SPEAKER_00 11:25

Totally. Thank you both. That that really helps that you're very much using your case presentation and then your post-mortem examination findings to really guide your uh actioning of diagnostic testing, but knowing that you've got that suite of samples that you could rely on if your testing draws blanks. So, Ed, could you guide us through the results then for this case?

SPEAKER_01 11:42

So uh we'll we'll start by going through all the various things that tested negative, which uh aren't exciting but are probably good news for the farm. They we did screen for PERS, as Toby suggested, and that came back negative. Looked for Lawsonia, and uh that was negative on PCR.

SPEAKER_00 12:00

Okay, so your PERS PCR testing would have been on spleen, which is as which is our tissue of choice when we don't see pneumonia at post-mortem examination. And then your Lawsonia PCR would have been on ileal contents.

SPEAKER_01 12:12

That will have been on enteric contents, absolutely. And we'll also carried out culture on the salmonella-specific cultures with no salmonella isolated. It was negative on PCR for various porcine enteric coronaviruses, which we uh look for PEDV, porcine delta coronavirus, and um TGE.

SPEAKER_00 12:32

Great. So that's porcine epidemic diarrhea virus, porcine delta coronavirus, and transmissible gastroenteritis. So these are three pathogens that we don't detect from pigs in Great Britain, one of which is notifiable. And this testing is completed under funding from AHTB. It's really helpful for proving freedom from those pathogens. And any pigs that are submitted to us with diarrhea andor enteropathy are tested using this PCR. So, Ed, what else did you find?

SPEAKER_01 13:00

Lastly, uh no evidence of Brachispira from the testing we do. So um we we carry out both PCR and also culture to make sure we we get a nice isolate for any whole genome sequencing if it is there. But fortunately in this case, it wasn't. So that's that's what we didn't find. But uh in terms of what we did find was we got some hemolytic E. coli isolates from these the small intestinal contents of two pigs. So uh when we're kind of in this age group and thinking about edema disease, we tend to culture distal small intestine. We did also get a non-hemolytic E. coli from from the third pig. And uh when we get an E. coli, we then try and characterize it a bit better. So in this case, um we've done some um very interesting PCRs. So we found uh hemolytic the hemolytic E. coli's had both genes encoding for F18 femuryladesin and STX2E, which uh encodes for uh sugar toxin to variant E, which is uh a toxin that's associated with with this uh clinical presentation in in pigs. Uh so that's nicely consistent with the diagnosis of edema disease.

SPEAKER_00 14:08

Perfect. So there it's probably important to note that you're taking into account both the findings on that virulence factor PCR as well as the clinical findings that support the diagnosis, because E. coli and even E. coli that possess genes encoding for virulence can be found in the normal pig gut. And also in pigs, both hemolytic and non-hemolytic E. coli can cause disease in pigs. So that can complicate things slightly, but we'll preferentially select a hemolytic E. coli if it's there for the PCR, which in this case has enabled this diagnosis to be established. So, Toby, can you talk us through then how edema disease comes about?

SPEAKER_02 14:47

Yeah, sure. So edema disease occurs when a toxigenic strain of E. coli colonizes the small intestine, proliferates, and produces this uh sugar toxin subtype 2e, which as Ed says is the subtype of sugar toxin, which is associated with DM disease in pigs, and distinct from the subtypes of sugar toxin, which produce say like hemolytic uranic syndrome in humans and disease in other species. Uh, and this I'll call it sugar toxin for shorthand, I think hereafter. It's a bit of a mouthful. So this uh sugar toxin is absorbed into the bloodstream and it causes damage to vascular endothelium in in certain tissues in particular target areas, especially the brain, the subcutus around the face and eyelids, the stomach wall, and of course the mesocolon. And you can also see edema affecting the larynx, which can result in uh sort of unusual vocalization or sort of squeaky type noises. So the um the lesions in the brain are probably what's causing death in these pigs, and if they present with neurological signs, then also neurological signs, of course. It produces cerebral edema and areas of necrosis in the brain stem. Edema disease typically affects pigs in the early post-weaning period, but we can rarely see it in other ages of pig uh in adults, say.

SPEAKER_00 16:01

Great stuff. And so you didn't complete histopathology on these tissues because you already had a diagnosis, so there was no real need to. But if histopathology had been completed on the tissues with edema, what would you have seen?

SPEAKER_02 16:16

If we do look at tissues uh with grossly evident edema, like the stomach wall or the mesocolon, then we would expect to see edema as expansion of the tissues, and we'll see evidence of microvascular injury. So that's injury to capillaries and arterioles in the tissues in the form of swelling of the endothelium, uh deposition of fibrin in vessel walls, and leakage of protein into the perivascular space. And importantly, you won't find any inflammatory process in the adjacent tissue, such as a bacterial infection of the mucosa, which would otherwise explain why there is that sort of endothelial activation and inflammatory edema. We'll often look at the brain in these cases to try and find the same vascular lesions and those areas of um brain necrosis and the brain stem. But oftentimes those lesions are actually very subtle and hard to find.

SPEAKER_00 17:09

Cool, that's really interesting. Yeah, it's interesting that you mentioned the lack of inflammatory process in the adjacent tissue because we do sometimes still see a bit of edema whilst completing a postmorseman examination due to bacterial septicemia, don't we? So, yeah, that's that's really interesting how histopathology differentiates those two causes.

SPEAKER_02 17:27

Yeah, for sure. Or if you've got like an enteritis or colitis, you'll often get a edema of the cirrhosa around the intestines, uh colon there as well. So it's yeah, it's finding that edema in the absence of actual enteritis is key.

SPEAKER_00 17:41

Cool. And do you always see edema grossly and or histopathologically in this case, or uh sometimes not?

SPEAKER_02 17:48

Yeah, no, no, not always. Uh in some cases, the cause of disease is more acute and you won't find any gross or microscopic lesions in in the brain or or in other tissues. So I think it's good practice to culture from the small intestine in cases of sudden death or neurological signs in in post-wean pigs, in case other investigations fail to identify an alternative diagnosis. That being said, um we we see uh cases of of clear sort of classic edema disease in post-wean pigs as well, and and don't manage to isolate sugar toxin producing E. coli. So it's important as well in these cases to to collect uh tissue samples for histology in case you need that sort of added assurance if if you've been unable to isolate the E. coli of interest.

SPEAKER_00 18:35

Yeah, that's a really good point. And there I think it's important for us to kind of put ourselves in the bacteriology lab for a moment and think that when the intestinal content swab is being plated up, we hope that the predominant E. coli will be the one that's causing disease, but it isn't potentially always the case. And and therefore we might end up effectively running that PCR test almost on the wrong E. coli.

SPEAKER_02 18:55

Yeah, it's it's the roulette of selecting the right colonies to subculture, isn't it? And making sure you you you're picking the right one.

SPEAKER_01 19:02

And when you consider that ultimately with the full length that you've got of the intestine, and we've got a swab from one small part of it. I mean, buy a lottery tickets now.

SPEAKER_00 19:10

Yeah, very good point, Ed. So we've actually developed an interactive learning resource for cases of nervous disease with recumbency, which edema disease can also present as. And it goes through diagnosis of edema disease as well as other conditions that can cause that clinical presentation. So we'll put a link to that resource in the show notes. And so, Ed, you didn't just see signs of edema in your post-mortem examinations of these pigs, did you? But you also found hemorrhage into the larger colon, which is unusual for edema disease. So can you describe why that might have occurred?

SPEAKER_01 19:43

Yeah, great, great question. And it's certainly something that we uh don't necessarily often find in these edema disease cases. It was quite uh exciting, uh, if you're as nerdy as me about pathology to see these. And in terms of the actual exact underlying cause of it, one thought would be this local effect of potentially the sugar toxin causing vascular injury um within the the mucosa and submucosa of the uh distilled small intestine and within the colon. Now, we've obviously talked about these kind of predilection sites and and how that's where we typically see edema, but it is possible that maybe we're seeing some endothelium injury in these in these other areas and other tissues as well.

SPEAKER_02 20:24

Yeah, so we think about these target sites, uh, but you can see evidence microscopically of endothelial injury in all sorts of tissues in the lung and in the heart sometimes as well. But of course, in those locations, those lesions are less specific to this disease, could be caused by other things.

SPEAKER_00 20:40

Cool. So I think we understand the pathogenesis for this first case now then, which shows a really nice investigation into this clinical presentation of pigs being found dead. Now we're gonna park any further explanations until we've talked through our next case, which does have the same pathogenic cause, sorry, spoiler alert, but is a bit less standard in its presentation. So, Ed, are you able to give us the case history for this next case?

SPEAKER_01 21:07

Absolutely. So uh these were some pigs from a commercial uh indoor far-to-finish unit. Uh so about nine-week old pigs, they wean at about four weeks, so these are kind of five weeks post-weans. And what they were seeing was neurological signs. It included circling, some head tilts, uh, head pressing, and then recumbent pigs reported to be paddling.

SPEAKER_00 21:31

And now I guess Ed's that that's where kind of videos come in is really is really helping us to that. If someone's struggling to kind of say, Yeah, I've got neurological signs, but I'm not sure what they are, getting the um either the keeper or taking videos yourself and getting those to us, and we can kind of do more of that picking apart.

SPEAKER_02 21:46

Yeah, videos are really helpful. It can help us narrow down the focus of the investigation to you know actually so what part of the CNS, if it is indeed the CNS that we're interested in.

SPEAKER_01 21:55

So uh and the other thing on the video side of things is the the veterinary investigation centers do have uh a a site WhatsApp now where you can contact us. So if the farmers pinged you one over on WhatsApp, feel free to forward it over and say, you know, this is from XYZ farmer that's coming into you today. And it really helps us to just have a little look and see what we're expecting.

SPEAKER_00 22:16

Brilliant.

SPEAKER_01 22:17

So um so alongside these neurological signs, the pigs were also uh anorexic uh and and had some uh joint swellings reported and this is an issue that seemed to have been affecting successive batches. Now not all necessarily affected to the same degree this this batch seemed to be worse so uh normally you'd get they they're reporting about five per batch whereas this time they were seeing about 15 pigs affected over over a period of time. So again we had that little chat are there any notifiable diseases that we need to consider before we say yes bring these pigs in. And this time they weren't actually reporting any deaths they were actually having to euthanise these pigs on welfare grounds and it wasn't resulting in these sudden deaths that had been reported in that previous one. And when we discussed the whole kind of clinical picture there didn't seem to be much else going on. It was restricted to these clinical signs we've discussed and we were happy that there was no suspicion of notifiable disease. But we did also want to rule out you know the other things we talked about is there any possibility of water deprivation? Pigs particularly susceptible and we know it can can result in neurological signs again. Had a chat with that in there there seemed to be no indication that there was any involvement of water deprivation and similarly talked about is there any possibility of either access to toxins or potential feed contamination or anything along these lines and none of that would have fitted with the the onset of presentation compared to you know when they changed diet or moved feed bins or anything like that. So right we've said we can uh look at look at some pigs um now the the only available pigs had been treated by antibiotics so obviously we had that chat with the vet to say you know that may well affect any bacteriology we do but they were keen to proceed and so then we also needed to discuss about how we were getting these in. They weren't having any deaths so there were none of those available to come in. So we needed to then think is it feasible for them to euthanise on farm and if not uh is it possible and practical to transport them into the veterinary investigation centre for for euthanasia while maintaining um appropriate kind of welfare considerations for those for those animals.

SPEAKER_00 24:26

Cool so I guess there the discussion between this admitting vet and the veterinary investigation officer is super important to understand firstly what would that on-farm method of euthanasia be and would that be a method that destroys brain tissue? If it is then that's not going to be ideal for a nervous disease investigation when when you might want to look at the brain and therefore it could be decided to be necessary for pigs to be submitted live but that is only appropriate where welfare wouldn't suffer as a result of that transport and where you're confident that they'll be transported carefully so that so that that was the case. And also that the necessary legislation was followed.

SPEAKER_01 25:11

In this case it was decided that with the size of pigs and um what was being described they were suitable to potentially bring in with many caveats surrounding the welfare throughout transit. So this was discussed with the private vector surgeon and and you know it is only done as a last resort um and where there's a valid reason for the investigation.

SPEAKER_00 25:34

Thank you Ed. So in this case then what happened when they arrived?

SPEAKER_01 25:39

So once these pigs had arrived uh we'll have unloaded them into our leverage and um just checked them over you know making sure we adhere to all of the uh the movement license things have to obviously make sure things arrived um as as they should have done we were happy with the state that they arrived in and one of the benefits of them coming in live is that we actually get to see the neurological behaviours for ourselves. So we can then carry out a little bit of a neurological exam quickly before then looking to to euthanize these animals humanely with an overdose of injectable anesthetic. And from that once they have been euthanized we can then start our diagnostic post-mortem examination.

SPEAKER_00 26:17

So what did you find? Very little very unrewarding post-mortem examination in that respect so a little bit of food in the stomach uh potentially a mild little bit of pneumonia uh but everything else very unremarkable great stuff thank you so Toby can again can I ask you to to put your problem solving hat on and consider what differentials you're wondering about in this case what diagnostic testing you would action in the first instance?

SPEAKER_02 26:44

Yeah so we've got a neurological presentation in this case with signs like circling head pressing and paddling pointing towards a condition affecting the brain. So we might start thinking about a bacterial or possibly viral infection of the brain so you probably want to take a swab from the brain surface perhaps take some small samples of brain tissue for for virological testing and then plop the rest into plenty of form to start fixing. And in this case we've seen some evidence of pneumonia as well probably unrelated to the neurological signs that have been described but we might wish to follow that up with some virology and bacteriology on lung tissue as well.

SPEAKER_00 27:20

Great. Was that along the similar lines of what you action did?

SPEAKER_01 27:24

Yeah absolutely so very much starting with with bacteriology from meningeal swabs and as Toby rightly says while we're here we've got some fresh mnemonic lungs we might as well follow that up even if it's not the main issue that these are presenting with and also looking for for PERRS and flu in those lungs as well. Because these pigs aren't being found dead and because at postmortem we didn't find anything to suggest you know a systemic infection that's again why we've not looked at doing swabs for to investigate septicemia you know there was nothing to suggest that in the pigs that we had in there was any systemic kind of bacterial infection. So we've we didn't pursue that and focused on that that meningal swab.

SPEAKER_00 28:03

Nice okay and so for nervous disease it's there are some really good reasons to submit to the lab on there and we'll discuss those in a moment. But there will be times that vets will either want or need to be completing their own postmortem examinations out in the field. And in that nervous disease resource we've put in a sampling aid memoir to help you gather the samples that you might need and then once you've done that you're very welcome to give us a call to decide what testing to action so to to call your local veterinary investigation centre and we can help you with that. So what did you find then Ed in terms of the results from your diagnostic testing?

SPEAKER_01 28:44

So uh similar to the postmortem not a huge amount in many ways good no evidence of PERS no sign of flu. Ultimately flu can be quite transient in f in its infection but that's I'm sure another podcast and bacteriology was was unrewarding but we had talked about there'd been previous antibiotic treatment so uh maybe that's partly the reason why as well.

SPEAKER_00 29:04

Okay, so what do you do now?

SPEAKER_01 29:07

Well that's where my wonderful um stash of all my other samples came to before and um I have a rifle to see what I've got and then go, ah, I know a guy who just loves to see these sorts of things. So I sent the brain down to Toby.

SPEAKER_00 29:20

Brilliant and I guess that's the real benefit here of submitting to a lab because that meant firstly the brain was intact because of the method of euthanasia used and then by being in that lab environment our wonderful PM technicians are able to remove that because of the extra equipment that we're able to use in that environment. And so Toby you've you've received fixed brain then and spinal cord I believe that must have been a big job Ed yeah the spinal cord I mean in this age group isn't so bad.

SPEAKER_01 29:50

We we had a spinal cord out of a bull the other month so we're very very grateful for the excellent support stuff and and uh they they can get it out nice and cleanly and make sure they keep all the nice little root ganglia that Toby loves to look at.

SPEAKER_00 30:04

Great. What did you see Toby?

SPEAKER_02 30:06

Yeah okay so uh on microscopic examination of the fixed brain and spinal cord in this case we found signs of chronic injury to small vessels in the brain stem consistent with a condition known as cerebrospinal angiopathy. And we wrote about this case in one of our monthly vet record surveillance reports and we'll put a link to this in the notes. And in that report there's a nice image of one of these vessels showing the vascular wall changes um including um sort of swelling and proliferation of the cells in the wall and the accumulation of highline droplets in the perivascular space which is so typical of this cerebrospinal angiopathy.

SPEAKER_00 30:44

Brilliant thank you and uh even I could see the difference on on those pictures which uh usually histopathology just looks pink to me so it must have been marked. Everyone can be a histopathologist so cerebral spino angiopathy can you tell us about this condition?

SPEAKER_02 30:59

Yeah so it's it's sort of well we believe it's sort of the the chronic manifestation of this vascular injury we've been talking about this whole podcast in the brain due to sugar toxin. The condition was first described in the 1950s and 60s and investigators at the time posited that it might be a form of enterotoxemia they drew parallels with edema disease because the condition was occurring in the postweaned pigs and at the center of of the the lesions were these as was vascular injury. And then experimental and observational studies in the 70s and 80s established the link with sugar toxin producing E. coli and edema disease. So pigs with cerebrospinal angiopathy typically present with nervous signs like ataxia and circling as well as a loss of condition rather than rapid mortality as we see with edema disease. Although there is some mortality but it's not usually as high as as cases of acute edema disease. And the ones that survive longer can be sort of quite stunted in growth. And at postmortem they generally don't have any significant edema of the tissues that we see in the acute formal disease.

SPEAKER_00 32:03

Cool okay and do we know why we don't usually see that significant edema?

SPEAKER_02 32:08

Not precisely but I expect it'll be because the endothelium in these vessels is experiencing a lower grade of injury that results in chemotaxis of inflammatory cells to the affected vessels and vascular remodeling but without the massive sudden egress of fluid and plasma that typifies the acute form of disease.

SPEAKER_00 32:25

Okay so I think this is really unusual right so I so compared to the kind of hundreds of cases of edema disease that you all have seen Toby I believe you've seen cerebrospinal angiopathy twice.

SPEAKER_02 32:36

Yeah that's right I don't know why but it's it's really is a very uncommon diagnosis in the UK currently or maybe I've just been missing them.

SPEAKER_00 32:43

Well what was strange was that you got two in about a month it was just really odd.

SPEAKER_02 32:48

Very odd very odd yeah I I don't think I'd seen one in the last 10 years maybe and then um then two a couple of weeks apart which is very bizarre.

SPEAKER_00 32:55

Really cool so we've only got two to go on but kind of looking at the literature and considering as well do we also find anesthes in cases of cerebrospinal angryopathy edge?

SPEAKER_01 33:05

I feel like all I'm saying in uh this particular case is we didn't find anything certainly certainly in this uh in our case here uh we didn't maybe have still on the show here hasn't he always sometimes you just need histopathology yeah I I believe in these in these sort of subacute chronic forms of of disease you uh bacterial culture of the intestine is is often unrewarding uh it's probably to do with the the chronicity of the condition the the sort of initial insult would have happened days uh or weeks ago I suppose and you know we we also were were hampered in owl and as well by the fact that uh there'd been antibiotic treatment and actually when we did come to to look um so I had taken a small intestinal swab but I hadn't sent it off for bacteriology at the time of postmortem I had no gross evidence of edema I was kind of still at that point possibly thinking more along the streps and in terms of um something we'll touch on shortly about ages affected these were nine ten weeks old they'd been weaned five weeks beforehand we were getting further away from that typical time period where we classically see edema disease cases so it may also be partly down to the fact that that uh the swab was only action for bacteriology a bit later than we normally would.

SPEAKER_00 34:22

Totally fair. But as Toby has already described that wasn't necessary for you to establish this diagnosis because the histopathological signs alongside the clinical presentation would have been sufficient in this case.

SPEAKER_02 34:33

Yeah that's right in this again in this age group uh these vascular lesions in pigs are considered pathognomonic cerebrospinal angiopathy you can see similar vascular lesions in in other species in humans as well in the brain due to chronic hypertension but the distribution in the brain is different it's more towards the cerebral cortex whereas in this case in pigs the the vascular lesions are centered more around the brain stem and spinal cord great okay so I wonder if we can pull these two cases together then so we've got the same causative pathogen which is a sugar toxin producing E.

SPEAKER_00 35:06

coli and then we've got different presentations in terms of clinical signs so one death one with deaths and then one with uh nervous signs without deaths. They're a very similar age is that always the case so so is this kind of nine to ten week age always the case for disease due to SX Ed from what you were saying earlier? Seems not.

SPEAKER_01 35:26

No absolutely so um what we tend to think of rather than necessarily the age of the pig is more looking at the how long since they've been weaned. So typically we're looking at a couple of weeks after weaning so in commercial pigs where you're looking at weaning at four to five weeks we're looking at more a peak around the six week mark. So in that first one probably one of the reasons we we saw it at that nine week mark is that we were uh obviously looking at ones that were being weaned a week earlier so we're still very much that kind of perian period. Now that's not to say that it can't occur at other ages so you know we can occasionally see disease in in adult pigs but it's it's not that common and we don't typically see it as a a pre-weaned issue.

SPEAKER_00 36:12

And actually the case that you referenced a few minutes ago Toby that uh so the case of cerebrospinalandiopathy that you diagnosed soon after this one that was actually in a CAW wasn't it in a in a totally unrelated disease incident?

SPEAKER_02 36:24

Yeah that's right as a single animal affected and uh adult CAL.

SPEAKER_00 36:28

And we described that case alongside the one that we're currently talking about in the vet record item that you referenced so we'll we'll put a link to that. So let's discuss these two different clinical presentations then in these two cases that we've got today. Do we know why some disease incidents due to sugar toxin producing E. coli feature this presentation of acute deaths maybe with some acute nervous signs but but actually with mortality being the main presenting sign. And then these other cases which are much more unusual feature this subacute form?

SPEAKER_02 37:04

Yeah I I don't think we really know as as you've already said we'd see the acute form of sudden deaths maybe nervous signs and edema much more frequently and this cerebrospinal angiopathy form um is rare or sporadic at best. And it might be to do with differences in expression of the sugar toxin or other virulence factors by the different E. coli strains that are around it might be to do with differences in enteric microbiome or sort of other factors that have influencing the development of disease or or host differences perhaps even in terms of susceptibility of the endothelium to injury by sugar toxin super interesting.

SPEAKER_00 37:39

So you've made these diagnoses then what about case management what Ed can the submitting vet and the farmer do to prevent future cases?

SPEAKER_01 37:48

Well ultimately we we've talked about how typically we see these cases around weaning and that kind of strongly suggests to you that there's there's clearly something going on around the weaning period that may be playing a role. So ultimately looking to reduce stress and dietary change around weaning so you know introduction of creep in fowering houses and things like that. But also looking at practicing good hygiene. So ultimately if you move from the fowering house into a place with a really high bacterial load then have already got massive shifts in your microbiome but anything that then might predispose them to having an overgrowth of of these strains um will be of relevance. And finally there there are some vaccines that the license against toxin producing E. coli strains that may prove efficacious in the management on farm.

SPEAKER_00 38:35

Great I think that's going to be super helpful to our listeners. And can I stay with you Ed to then give us your take-home advice for vets investigating these kinds of cases.

SPEAKER_01 38:44

Absolutely something when you do have these combined cases of mortal increased mortality and nervous signs you want to be thinking about checking the water supply and that's not necessarily just checking it but also checking that pigs are drinking from it. So you know it might be fine you've provided them with plenty of water but actually it's a height that none of them can reach I think toxins will always be something to also just bear in mind and think you know has there been the introduction of anything new? Is there anything unusual? Are you noticing anything that's that's a bit odd if you've opened up any pigs on farm have you noticed anything in the gastrointestinal tract? So toxins uh and that's particularly relevant on on smaller holdings where um you know you might be moving paddocks more frequently or you might just have a little bit less control over things compared to kind of uh an indoor commercial unit. If you do have pigs that have been found dead then the veterination centers uh would always prefer to have a carcass to work with it just allows us to have a really good thorough look over and make sure that we kind of can see everything. Ultimately removing the brain and spinal cord on farm can be tricky. Toby would always rather get a whole brain rather than one that's a little bit smushed and cut in half. Yeah absolutely if you do have any case of of nervous disease and and need to euthanise these pigs for submission then have a think about how this can be done humanely and without destroying the brain. If it can't then then discuss with us and we can see whether it is one that might be suitable to come in or if not we're more than happy to advise on samples. Feel free to give us a bell have a chat send us a WhatsApp videos absolutely really encouraged. And and then if you have any particular thoughts yourself um just you know when you're sending in a submission form be sure to put that on.

SPEAKER_02 40:33

Yeah I agree I think the more information the more context that's provided around the case is going to improve and and refine the our diagnostic process and improve the comments that we can return.

SPEAKER_00 40:45

Great. I think that has been really helpful thank you both.

SPEAKER_01 40:48

Toby have you or Ed got anything to add before we wrap up I think that just that these can be some of our most interesting and some of our most challenging ones sometimes these these neurological ones and we always like to hear about them even if you think you know what it is if you've not had a diagnosis to confirm it you never know it could be something a bit weird and wonderful. So yeah we're always happy to to see these cases come through and investigate these.

SPEAKER_00 41:14

Amazing so all that's left to say then is our thank yous. So thank you so much to the submitting vets and farmers for these cases as well as for all our previous cases that have allowed us to build up this knowledge base into these conditions. Thank you so much to everyone at APHA who's contributed to these investigations particularly you Toby and Ed and for walking us through these cases so nicely. And finally thank you to you our listeners we'd love to hear what you think about the podcast and what you'd like us to discuss in the future episodes. See you next time