So everyone, it is a pleasure for me to have been asked to prepare this webinar on investigating ill drift in use. I hope you'll find it useful, and if you have any further queries, you can contact me at this email address. Valentina Guin, I graduated from the University of Turin in Italy in 2007, and I've worked in mixed and farm animal practise for three years before starting a farm residency and obtaining the diploma for the European College of Small Ring and Health Management.
I'm currently working as a general clinician at the University of Glasgow and I'm focusing mainly on farm animal disease investigation and surveillance. Before diving into the topic, I would like to let you know what we'll be covering in this lecture. First, I'll give you an overview of the definition of ill drift and what key performance indicators or PPIs are significantly affected.
We'll then move to the common causes of ill drift in use in the UK. And then we'll conclude with some insight into diagnostic tools and potential solutions when investigating this problem. Throughout the presentation, I'll also point out an economic considerations that are associated with the problem of field drift.
The case definition of i drift in adult use should include all those animals that despite normal appetite, are presented with below target body condition, either as a result of weight loss or failure to gain weight. To decide whether an animal fit this case definition, we also need a measurement of the condition of the animal and also a reference value for the animal. For the measurement that is in the form of a body condition score is yes, which is the standard method that we are all familiar with, and that's a 0 to 5 point scale, sometimes we have score in between, and it's the assessment of bone prominence and fat cover by palpation of the lumbar region as you can see in the picture on the right.
What we need to remember regarding the body condition score is that this is a subjective measurement, so reputability within and between assessors is probably the main limitation of this technique. Obviously also it can be quite time consuming. To overcome this issue, what I would suggest is that you make sure that farmers or whoever is is doing the body condition score have experience in this technique.
For example, what you could do is to assess the same few animals independently and then compare the scores and see if you agree on the on the score for, for those animals. And the other thing I would suggest is that you could actually provide training, and that's a very good opportunity to to get involved in the flock and also to to make your clients aware of the importance of both the body condition score and The cases of ill drift within the flock. Another thing to remember is that body condition score should really be done regularly throughout the year.
The, the key moments to body condition score are the ones reported in the tables, so they would be mating, admit pregnancy usually about 6 to 8 weeks before, the landing, and then it, and what you see in the table is also the reference value, as you can see also with the bullet point, obviously you need reference values to compare. The scores of the animals to what it is expected and what you see in the table, is exactly the reference value that you would expect for, those production time and for the type of the type of view. Apart from the obvious low body condition score, blocks with an n drift problem are also affected in other ways, and that's where looking at key performance indicators, KPIs, is really useful as well.
And these are data that are collected on farm for different production characteristics. The ones that I want to focus on because they are significantly negatively affected by air drift are the three you can see here, breeding performances, lamb production and new longevity. For breeding performances, we are looking at things like low scanning.
Or a high number of bars for lamb production, and that's usually evidenced by a lower number of lambs that are either marked or turned out after landing, and that's usually connected to an increased neonatal mortality or as a consequence of less viable lands. And then obviously, your longevity that's directly related to either increased cal rate because they are nobody can score or an increased mortality rate, in the flock. So, what are the main differential diagnosis for ill drift?
Well, first of all, what I like to do is for you to take some time and pause this recording and try and answer this question. What are the common causes of ill drift in use in the UK? A useful resource to actually gather this information is from the link you can see below, which is the Great Britain sheep Disease surveillance dashboard, and that gathers all the surveillance information from submission to the veterinary diagnostic Network.
One thing I'd like you to remember before we, we move to the next slide and, and see what are the common causes is that an ill treat problem in a flock is very likely to be multifactorial. So usually more than one disease or more than one syndrome that might be involved. Personally, I would list all the main differential diagnoses under these three categories, inadequate nutrition, parasites, or infectious diseases.
And this picture on the right, I think it really summarised them all. So what you can see is that within inadequate nutrition, we're talking about an inadequate supply, so a lack of food, inability to ingest related to periodontal disease, or related to lameness. As lame animals are whether you can offer as much food as they want, they might not be able to feed.
One point here is that I'm not gonna cover lameness, but please, really remember that this is also a cause of ill-try. Regarding parasites, these would include primarily chronic liver fluke, which is the picture on the left, and parasitic gastroenteritis RPG, which is the one on the right. And finally, for your infectious diseases, the main one causing ill drift would be OJD yoni's disease, ovine pulmonary adenocarcinoma or OPA, sheep scal.
He's used lymphadenitis or CLA and Medina, or MP. So let's look at the first one of the most common causes, and inadequate nutrition, and this is defined as an imbalance between demand and availability of nutrients and probably is the most common cause of interest, as well as being in, in my opinion, probably the most difficult to diagnose, but also to address with the farmer. Sometimes inadequate nutrition might be due to inexperience, for example, we call the farmers, but usually it either relates to inadequate supply, which is related to the level of production in The typical example is in late pregnancy where feed availability is scarce, but demand is at the highest, or the supply might be uneven, so there's enough food, but it's not distributed evenly across the flock, and that could be due to inadequate feeding space, overstocking or competition, and this usually happens indoor.
To, to, to address this problem, as I said, that's probably one of the most difficult one to address with the client, with the farmer, you really need a good discussion, with the farmer. I would suggest potentially involving a nutritionist. And definitely you need a farm visit.
You want to see the feeding, and you want to assess the feeding regime, so things like the quantity and the quality or the palatability of forage, the, the type and the amount of concentrated feeding, but also the feeding management. So things like space, frequency and timing, the age groups, the stocking density. So it really is about Getting as many information as you can, from the farmer.
What I would say for regarding the low body condition score is that inadequate supply usually presents with a general low body condition score across the whole floor. While when we have an even supply, so, there might be enough food, but it's not available for everyone, then usually you would have a considerable variation among body condition score. So some might actually be even over conditioned and some will be under condition with some in the, in the target, in the target score.
As I mentioned before, if nutritional supply is adequate, then there's also the possibility of inability to ingest. And that's mainly due to periodontal disease or what is commonly known as broken mouth. I would say that, this condition can be quite challenging to diagnose.
It, incisor we can obviously be easily assessed in the live animal, as you can see from the picture on the left. But unless it is so extreme as in this case where you have a complete loss of incisor, it might not actually impact as much on the feeding ability as we think. Molar teeth where instead is much harder to assess in the live animal, probably, it is a much more frequent or a more important cause of, you know, drift.
So you can also use a mouth cap to assess the molar and pre-molar teeth, but in my experience, that it is quite hard and, and it is also very time consuming. So what tends to happen is that this is diagnosed at postmortem as you as you can see from the picture on the right. In this case, in the picture, what you see is a loss of molar teeth from the maxilla, and there's gum pockets which were actually impacted with food material and there's also loss of mandibular teeth.
You can imagine how a case like this one would be hard to diagnose in life. But the degree of periodontal disease that you can see here is so severe and so advanced that definitely would have caused ill drift in this animal. Unfortunately, compared to other sheep disease, periodontitis or, or broken mouth, have not been researched as much.
So the, the causes of of this still are a bit unclear. There's suggestion that it could be due to pathogenic bacteria, it could be due to feeding or root crops, or potentially a lack of protein in the diet, but still, we don't have really a definitive answer for the, the reason behind young peridontiti and probably it would be a multifactorial. I would say there's also a lack of clear evidence on how much exactly this problem impacts on the animal condition.
And finally, unfortunately, not much, can be done, apart from, premature culling of of the affected animal. We'll now moved to the second of the three main categories, and that's parasites. And as I mentioned before, chronic liver fluke on the left and parasitic gastroenteritis on the right are the internal parasites which are mostly responsible for ill drift.
So I'm not gonna expand anymore or, or too much on either of them as, as I would say that would probably require a whole hour each. But what I'm going to do is just to highlight a couple of key points that are important to remember in the context of Edrift. So what I would say is regarding liver flow, that any age really can be affected as animals don't develop immunity to the parasite.
Chronic liver flu is also a seasonal problem, so you would mainly see it in the winter and spring, but just be aware that due to wetter and warmer conditions, this seasonality is actually expanding a little bit. For the diagnosis, then that can be done through accounts or you can request abattoir reports. And one last important thing I would stress for chronic liver flu is that obviously you can use any licenced fluicide to treat it, but please obviously be aware that Tricabendazole shouldn't really be used in these cases and should really be reserved for in mature flu.
Regarding nematodes, or parasitic gastroenteritis, and again, a couple of things that I really want to, to remember in this context are that although you should have developed immunity, they should have acquired immunity, that doesn't always happen, and And there's now evidence that it could actually subclinical parasitis can actually have a significant impact on adult animal performances. So, just because our adults don't assume that they're not affected by parasitic gastroenteritis, by nematodes, or whether, another important thing to remember is that we're not obviously advising to treat all adult use and to improve their body condition score, rather, Monitoring of parasitic gastroenteritis should be done in adult animals as well, not just in growing lambs and should be included as part of the parasite control in the flock. And finally, infectious diseases.
As I mentioned before, this is the list of the main ones in relation to ill drift in adult sheep. So we've got ovine neonis, OJD, ovine pulmonary adenocarcinoma or OPA, sheep sc, Caus lymphadenitis, or CLA, and Medisa or MD. One thing I'd like to point out here is that in my experience, infectious diseases are always blamed or very often blamed for ill-treat, and we always look for them in the first instance.
But although they might be the main responsible in some cases, a lot of times they are contributing factors, and all the possibilities I've listed so far should really be taken into consideration. The first one ovine Joni's disease. Again, I don't intend to cover too much about Joni's disease, as you are probably familiar with the same disease in cattle.
So rather than repeating it here, I'll point out the main fundamental differences between this disease in cattle and in sheep. And these substantially are the lack of the typical water diarrhoea, while the major clinical signs of illness in sheep is actually severe weight loss. Other signs include submandibular edoema or boo, which is due to hyperpromia and more break.
There is usually usually normal or even increased appetite and a reduction in general immunity, which might predispose to other diseases, which are mainly bacterial infection or they could present with a high parasitic margin. Espercato, the long incubation period means that the clinical signs are not usually seen until later in life, usually in adult she over 2 years of age. Due to the lack of specific clinical signs, ancillary testing are required for your final diagnosis.
Diagnostic tests are available and they are exactly the same as in cat. Be aware that the ELISA test in subclinical cases is called an even lower sensitivity than in cattle. Postmortem pathological changes are pretty much the same as they are in cattle.
One notable peculiarity of OJD is the occurrence of an orange yellow pigmentation of the intestinal mucosa, which is caused by a pigmented strain of math, and you can see an example in the picture. At the bottom right. However, a spectacular, as you can see here and very rewarding when you, do a postmortem and you find something like that.
Unfortunately, it occurs only in a minority of cases, so don't expect to see it too often. Finally, an important thing about OJD is that there is a licenced inactivated vaccine we use in small room, OK? And that would prevent the clinical signs and reduce mortality in vaccinated flocks.
However, just be mindful that it does not prevent infection and it, it might not reduce the bacterial shedding as significantly. And, and, I would say that's probably the main thing that you, you would have to remember about OJD. The second one we are covering is ovine pulmonary adenocarcinoma or OPA, which is a progressive viral-induced lung tumour of sheep.
And it's caused by Yit sheep retrovirus or JSRV. It is an iron-borne disease, so it is transmitted by inhalation of aerosol cell-free particles from infected animals. There is an age-related susceptibility to infection, which means that neonates and lands younger than usually 10 weeks are the ones that are most susceptible.
And the reason is that the cells, that the virus targets, which are the type 2 pneumocytes in the alveolie are actively replicated in this age group. Incubation though, is very long and can go from 6 months minimum to 3 years. So, it is rarely seen, this disease is rarely seen in animals less than 7 months old, and usually you could see in sheep that are 3 to 4 year olds.
The clinical signs, well, they include, weight loss and exercise intolerance. You can also have some more specific respiratory signs like tachypnea, nasal discharge, and if you listen to the lungs, sometimes you can hear crackles or harsh lung sounds. There is, at the moment, no live diagnostic test for OPA, so, you can, you can try the wheelbarrow test that you see the picture on the right hand side where, if there is a copious amount of clear fluid from the nostrils, then you have a positive diagnosis of OPA or you can try.
To scan the lungs to identify the lesions. But at the moment, the final diagnosis is still made at postmortem, where you find the typical lesions, and those are in the picture at the bottom right, and these are large grey masses that are very firm inconsistency. These are quite typical, pathological changes.
So if you, if you get to see them, then you'll recognise them fairly easily. The third one we're covering, sheep'sc is an allergic dermatitis, which is caused by the non-burrowing ectoparasitic mite called soroptisois. The disease is transmitted mainly by direct contact, but, what I want you to remember is that the mites can survive off the sheep, for about a few weeks, and they are infected for up to 16 days.
So fences and handling facilities can also provide a source of infection. The clinical signs and they are related to the faecal deposition of POI antigens and allergen on the skin. So as I said, it's a, is a dermatitis, it's an allergic dermatitis.
And this causes an inflammatory reaction, so you would have intense situs, you would have pyodermatitis, severe ropecia, and it all results in considerable weight loss. That's why it's under the ETrift list. What you see in the picture on the right is probably an extreme case where there are obvious clinical signs, but that doesn't always happen, because you also have a subclinical phase of this disease where the clinical signs might be quite subtle, so there might just be a bit of puratus.
This subclinical phase can last between 2 and 8 months. So, if it's, if shisa is present in the flock, it's just been introduced in the flock, you might not see this, . This obvious clinical signs.
Regarding the diagnosis, there's a skin scraping, so you can do a skin scraping and look for the mice. And now, just recently, Alyza and then direct Eliza is being developed and is commercially available and what you can do is basically detect both the subclinical and the clinical disease from blood samples. The 4th 1 in our list is Caius lymphadenitis, or also called pseudo tuberculosis, and this is a contagious disease that is caused by coronary bacterial pseudo tuberculosis.
The bacteria will enter the host through skin lesions. And there are two main forms of this disease, a superficial form where there is a cessation of the superficial lymph nodes. In the UK it's mainly the, the one of the head and neck, and then we have a visceral form which is the one that usually cause ill drift, and so that's the one that we're interested in in in this lecture.
And usually you would have lymph nodes affected and could be the mesinal or the bronchial, or the pulmonary lymph node. As you've noticed, there's no picture in this case, and the reason is I've actually never seen the visceral form, so I'm not, obviously, it exists, it's been reported, it is something that can cause ill tricks, so please keep this in your list of differential, but it's probably less common than the superficial form. For your diagnosis, you can, obviously for the visceral form, you would need to do a postmortem, and what you can, you can do is to confirm your suspicion by isolation of the organism from the abscess or you can take blood or from, from the live anymore or a postmortem and and request for analyse a test.
And then our last infectious disease to finish off the list of differential diagnosis in case of ill drift in adult animals. So this is Medivia or MV which is a, a chronic progressive and in proliferative disease. The, the etiological agent is, a non-oncogenic lentivirus, medivina virus, MDB, and the main route of infection is from the mother to the offspring through the lostrum and milk, but, it can also be transmitted by a lung secretion.
Like OPA, there is a very long incubation period and the clinical signs are not usually seen before a 3 year olds. So, so usually it's in adult animals. What are the clinical signs?
So, maybe in the list of ill treats, so, weight loss ill rift is the main one. You can also have respiratory, signs, things like, exercise intolerance, progressive tachynia or dyspnea, and sometimes you would also have other signs like induative mastitis or arthritis. The diagnosis of Medina is done in the live animal with antibody detection that's commonly done with an analyzer test or a postmortem again.
And in that case, you would see that lungs that are very firm, rubbery, and quite heavy, and they tend not to collapse, and sometimes you can see the imprint of the ribs. One thing I would point out again regarding the picture is that this is not one of my picture and although many business, I would say it's it's fairly common, unfortunately. Again, it's not something I've come across as much compared to other diseases, and again, I want to take a just just a consideration here to let you know that it really depends where you work.
So I've tried to make this list quite exhaustive, and looking at all the disease that are present in the UK that are . And a list of differentials for ill drift, but depending where you work, you might see some that are more common than others. So, you really need to know a little bit about what's what's present, where you're gonna work.
So as I say, this is a, this is the complete list you would have, but some of them might be more common in, in the area where you work compared to others. And now we'll move on to one of my favourite topics, diagnostic tools. And one thing I would like to point out before we go on is that an important step in any investigation, no matter what the problem is, is actually to decide whether the further diagnostic or ancillary tests are needed, as you should only do further tests if the results that you're going to get are actually influencing either your own or the client's decision.
In case of interest, well, you have two main options. One is to do postmortem examination or to sample examine live animals. If you consider the reduced value of ill-driven sheep, then I would say that the cost of a full postmortem, including the associated laboratory testing, is probably the most cost effective tool you have.
And you can think that a subsidised postmorte. Usually would cost around at the moment I'm recording it around 60 pounds per car or you can you can have sometimes batches of 3 to 4 animals for 100 pounds. So sacrificing some animals for postmortem is definitely cost effective.
You can also do an on-farm postmortem, and what you can see at the bottom is a link, it's a resource that will guide you through onfarm PM. The decision to either send the carcass to the lab or do the on-farm PM depends on many factors. Some are obviously due to geographical location, if you're not near a postmortem room, and the cost and time, and you have to consider that.
If you do. An on-farm PM then you would have to potentially pay for all the additional tests, but sometimes it's quite, it's quite good to show the farmer, what's going on here and there. So it's really up to you whether you go for, submitting the carcass or doing it yourself.
And the other option is to, examine sample live animals in case of the drift, I would suggest you concentrate on the areas of concern, things like the mouth, others, and the lungs. You can collect blood and faecal. Sample and for blood you can look at things like microinflammation, so that's globulins and the long term protein status and that's.
You can also do serological tests and they are for OJD sheep's cub CLA and And finally, the faecal samples, and they can be examined for either faecal counts or parasitic gastroenteritis and for liver flu. You can also do a coral antigen, Eliza for liver flu, and finally a faecal PCR for OGD. One thing to consider is to pull faecal samples, and I will just be mindful that the samples should be collected individually at the farm, and they will be pulled by the lab staff.
The other thing to consider when sampling is also the storage of samples, that's quite crucial, and the results are going to be reliable only if the samples were collected, preserved, and transported properly. So just be aware of of this as well. And the final thing to remember when thinking about diagnostic tools is how many you should sample which animal.
That's actually pretty crucial as well as deciding what test. So that's where the clear case definition is absolutely important for deciding which animal you're going to sample. Don't, don't sample randomly, but make sure you include the one that fit the case definition.
For the number of, of animals, again, remember it's a flock problem, so one animal is, is not enough. For postmortem, I would, also, suggest to try and select carcasses that are quite fresh, so a maximum of 24 hours between death and postmortem. And for the clinical exam in the blood sample, try to avoid excessive stress or things like lack of water or food before sampling.
For the number, you can actually be quite precise and use epidemiological tools that are available online to calculate the number of animals to sample. Or you can look at laboratory guidelines. So for example, for a postmortem, then I would definitely suggest 3 to 4 carcasses at least.
You would want to blood sample probably at least 6 animals and for faecal samples, usually it's recommended around 10 animals. And to conclude, what are we gonna do? What are the potential solutions where we are investigating in TIFF.
So first of all, no matter what the diagnosis is, and probably not even No matter what the problem is, remember that any investigation really starts with that conversation with the farmer. You need to look at some data, definitely before you carry out any sampling, and what I would suggest is you want to As I said, have a proper conversation with the farmer, set some achievable goals for the client, and then really monitor the progresses. It's, it's really a long term game.
It's not an easy fix for any type of problem and definitely for you. What I would suggest is that you find out exactly what the aim or the aims of the farmer, the client are, and then work with them to achieve them. We, we should be seen as offering some advice that is based on our knowledge and experience and not to be forcing action upon them.
Another important thing again, I would say this is a general for any investigation is that farmers should really be encouraged to work to work preventive medicine. That's what we should all aim for things like robust quarantine procedure and routine monitoring of relevant diseases and even more when we are talking about. In the specific case of LTRF, what I would say is that probably you would want to put in place a plan for regular monitoring of score.
That's definitely the first thing to do. This will allow you to provide some continuity on assessing. The problem and it's also a tangible and extremely cost effective way to assess the performances.
As I mentioned before, I would suggest a minimum of twice a year and you can either do the whole flock or a random proportion of them. The other thing is obviously to regularly review the the the KPIs that I mentioned before, so scanning records, number of lands that have been marked or turned out, and then. Obviously look at the cow and death rate, and that's again, a way to both monitor the progresses if you're making any changes or Obviously, as I mentioned before, that's also the way you start understanding a bit more about the problem and also provides a good way to keep the ball rolling with the farmer.
Another important thing or another sensible advice would be to regularly screen animals for endemic disease or disease are endemic on the farm. This can be done through either regularly monitoring of fallen stocks so you can postmortem some of the animals that go for culling or for product. Or you could select intrin animals.
So the same as you would do for your diagnostic tools, you can do it as a monitoring process as well. Well, this is me coming to the end of this webinar. I really hope you found it useful and have some, food for thoughts to go away with.
What I would say is ill-rift is really common, common, problem in flock up medicine, and it is also quite challenging in my opinion, and whether what I would say is that the investigation of irift problems in flux can also be very They rewarding and it's really a perfect opportunity to become involved in flock medicine. And now, and I hope you'll you'll all be off and making sure that we don't see as many sheep as the one in the picture here. Thank you.