Good evening and welcome to tonight's webinar. Hopefully you've had a pleasant day and the er weather has continued to be fine where you are. I'm Rich Day.
I am head of sales for the webinar vet, and I'm delighted to be the chair of tonight's webinar. As you may guess, as being head of sales, I don't have a veterinary background. So obviously, please do, when, putting in your questions, please type them fully, so that I can read them out to our tonight's speaker.
Shorthand, I am learning the shorthand of the the veterinary sector as I go, but there's still a few bits that I'm still unsure of. So please, if you're putting in questions, I do encourage to put in questions, you can just do it quite full, so I can then read them out, that'd be fantastic. So, many of you I'm sure have joined us previously on webinars, so you know exactly what to do.
For those of you who are new or haven't been on for a while, I'd like to say I'm joined by my colleague Dawn this evening. Dawn is, keeping an eye on our office emails. So if you do have any issues, please do, email office at the webinar vet.com, and Dawn will be on hand to answer any questions that way.
Alternatively, if you, go to the bottom of the screen and there's a little icon that says chat, click that and then you can type a message and Dawn will respond to you there also. As I mentioned, we do encourage you to post questions throughout the presentation. There will be some time at the end, for Rob our speaker to answer any questions.
And there is plenty of time to answer questions and also, get onto the telly in time for Love Island, which I know Dawn is desperate for. So, on to tonight's, speaker. Doctor Rob Kelly, graduated from the University of Liverpool with an MSC in veterinary Parasitology.
Rob firstly worked in mixed animal practise in the UK and has also been involved with various clinical research and knowledge exchange livestock livestock projects in Latin America, North and the sub-Saharan Africa. Rob then wanted to complete a part-time PhD in tropical epidemiology with the Roslin Institute, including conducting field work for 2 to 3 years in Cameroon, investing, investigating parasitic and zoonotic diseases in cattle. After working as a livestock clinician at the University of Glasgow, gaining fellowship of the Higher Education Academy, Rob returned to the Royal Dick School of Veterinary Studies in 2016.
This is where Rob is currently found as a lecturer and clinician in farm animal practise. With a passion for teaching and clinical duties, he continues to combine his interest in clinical, livestock, medicine, parasitology and one health. So for tonight's webinar, assessing impact of ruminant parasites, the why, what and when to sample in farm animal practise, I'd like to hand over to Rob, over to you.
Thank you very much, Rich. That was, quite a nice introduction there. So tonight, I'm, I'm just gonna really talk about, something that, a lot of our students and, recent graduates talk about as a, as an issue when they're trying to deal with para parasites in ruminant practise.
Sometimes it's seen as a little bit of a difficulty to try and understand what parasites are doing to animals and when to treat and when to take samples. So, What my main aim of this, lecture is, is just to try and dispel some of those fears and, and problems that people have when they feel daunted about, tackling ruminant problems on a, on a farm level. So, giving you some learning objectives just to try and hang all this off from.
So my main kind of points that I'm trying to, get across to you this evening are to try and estimate, the impact of parasitic disease, because most of these, parasites, you will find in most livestock farming systems. So it's trying to define when we need to do something and when we can just leave them alone to do their own thing. In doing so, we need to use diagnostic tests.
So I'm gonna give you the pros and cons of using different tests, and sometimes you might not even need to use tests as frequently as you think. So, there isn't a one size fits all approach, and that's something I'll try and emphasise throughout, this session. And then I'll try and give you, a few examples about the different thresholds that you might want to intervene, with parastatistic diseases using some cases that I've encountered, in practise as well, as working in the university sector.
So, trying to give you some examples of how, you can apply these, diagnostics, for intervention programmes. And as I say, I'm more than willing to answer any of your questions, and if I don't know the answer, I'm happy to get back to you afterwards. So, the first, part of this lecture, I'm just going to review diagnostic test selection, and this is something that a lot of our students absolutely hate because they think it's all to do with statistics and a lot of maths, and that's something that I kind of wanted to dispel.
And want to just kind of bring home to you a kind of simplified, kind of schematic way of thinking about how you might select a diagnostic test. And you can use this also in, when you're trying to, use and select other, diagnostic tests for other infectious diseases. So, you'll all be aware of the impact of ruminant parasites across the globe.
And just try try and hang this off something. I'm mainly going to talk about helminths in this lecture, so the gut worms and the liver fluke, but I will mention other diseases as applicable, that are caused by major parasites in the UK. On a global scale, livestock really are very important, as you'll all know, and approximately 10% of the world's population rely on them.
In all of these populations, regardless of where they are in the world, helminths are ubiquitous. So they're the most important in my eyes and in a lot of people's eyes, infection in ruminants, and it's something that we've got to learn to live with. From a UK perspective, the nematodes cost around about, 80 million, per annum, and that's quite a difficult figure to try and quantify.
So, when we're looking at that figure, from an individual herd or flock level, we're looking at direct production losses such as meat, milk, milk and wool losses. Benchmarking in health plans, so these additional costs for monitoring for these diseases, feeding animals for longer when they've been impacted by parasitic diseases, and direct control costs such as, implemented treatments, rotation of pasture, extra, use of labour. So think about these things when you're trying to convince, a stockman to control for these parasitic diseases, because they will really, require some kind of level of control, on the individual, holdings.
So how do you approach, these investigation on individual farms? I'm sure this is not new to any of you, that you would ideally conduct a farm visit. And that's really important because each system is very different.
The parasite biology and ecosystem on farm will be very different. Even if they're in the same area of the country. And doing a farm walk around, seeing what the fields are like, seeing what the stocking densities are like, etc.
Is really important, and I can't emphasise that enough. Get on farm and have a wander around. And you can try and do this when you're doing other things on farm too.
Then you can look at what diagnostics have already been done, and you might then decide to do some further diagnostic tests, depending on where you've been brought into in, the kind of disease control programme. Whether that's in an outbreak or whether that's to review, parasitic disease, and impact when you're looking at herd health plans. And then you can try and design interventions and surveillance practises with diagnostic tests to decide what to do next.
So all of this is really important, rather than just dishing out some anthemmitic over the counter. So, how we, approach an investigation really depends on the priorities of the farmer, so what are they seeing as a problem, and that might be clinical disease, or you might have to try and convince the farmer that it is worth investigating these problems and trying to quantify the impact of parasites. And that's related to what we think is important too, because there's no point in just treating something that isn't there or not treating something properly.
And then there's also the market priorities. So if these parasites have an impact on, meat and milk and wool production, we need to kind of, try and tackle these, to provide an, a good economic system. So, when we're looking at these priorities, I find this a useful way of thinking about, what the priority is currently.
And some of these are, interchangeable, and you might find different priorities on, the same farm. But ultimately, when you're presented with, reviewing, how to, investigate parasitic disease, think about what is the priority here and what do we need to do. So clinical priorities just briefly are looking at, you know, an outbreak essentially.
So we're reacting to illness and disease that we're seeing on farm, and you're often using diagnostics here to confirm a clinical diagnosis or rule out differential diagnoses. Production or economic priorities might be looking at that you're trying to be proactive proactive and identify inefficiencies in the system, so improving outputs such as growth in animals. And then there's the preventative priority when we're looking at and trying to minimise the impacts or prevent any further impacts on a farm.
So when do you need to intervene in control practises, on farms? So think about why we're using diagnostic tests on individual farms, and you need to do this with the farmer and have a really good discussion about it and try and grasp, that underlying, problem. So when we're looking at a diagnostic test selection, we firstly need to take a good farm history, as I've described, getting out on farm and understanding the farm is important and specific things might be important to look, look at when we look at considering helminth parasites are grazing practises.
So what are these stocking densities? What are the interactions between these Animals on the farm, because these parasites will be transmitted between different, animals on farm, primarily sheep, parasites and primarily cattle parasites. But there'll be different risk groups within these, groupings, such as lambs being more susceptible to parasitic gastroenteritis, for example.
How often amalytic treatments are conducted, so how often are we trying to get rid of these parasites and how, and that might affect, how our diagnostic tests perform, but also how we identify disease on the farm. And quite often, actually, we're using these tests at an individual animal level, but we're looking at the population impact on that farm. And that's something that's really important because often our understanding is of how these diagnostic tests perform in the individual animal, although we're using these tests to, identify control practises at population level.
And that's really important to think about because if we're diagnosing, an infection in one animal, is it actually having an impact in the rest of the, the herd or flock? So thinking about, the signalling, so what's the history of the animals on farm, doing clinical exam exams, thinking about is clinical disease present, or is it actually that we're not detecting any clinical impact here and we need to do further diagnostic tests. And what's the history of parasite control on farm and what's going on in these animals?
Because control practises and previous treatments might affect your diagnostic tests, but it might also affect your intervention, in future. Another really major point is thinking about the environmental conditions, and that's something that we don't necessarily think about with other infectious diseases, in livestock. Environment really does affect these parasites, and I often think about helmin parasites as an ecosystem.
So there's a population of infection, in the host animal, and there's also an Infection within the environment, so the refugia population, or the, transmissible stages of that parasite. And, you know, you need to think about where these parasites are, because there are a lot of them, what time of year they're likely to be around, and how that might influence how you detect these, parasites, with your diagnostic tests. So it's really important to think about, your life cycles here and having a good grounding in parasite biology.
So then moving on to the tests, themselves, do we need to provide further evidence? And, you know, you might actually have a kind of clear picture of what you're trying to look for and what the priorities are when you're selecting your diagnostic test, but what are we detecting? Is it infection, or are we trying to detect disease?
And that's something that can differ between different types of infection. Because a lot of these parasites are inevitable, and hence infection does not always imply disease. So for some parasites, such as the gut worms, there will be a normal burden with, adult animals, and they'll have developed immunity.
And it's when this immunity wanes or hasn't developed that you end Up with a large parasite burden, and you might get disease. However, some animals may have a low parasite burden with disease because they have poor levels of immunity and genetic resistance. And this balance might tip depending on, how old the animal is, if they've developed an immune response, or whether they're actually genetically, Resistant or resilient to parasitic diseases, and that's, that's something that might vary between different parasites.
So it's worth bearing that in mind. For example, immunity to oscetaceous species orcupius species take 1 to 2 grazing seasons to develop, and you often only see disease in neonates because adults are immune. However, Parasites like cattle, lung worms, Isocorlis can take one grazing season to develop, and it needs re-stimulating each grading system or that immunity wanes.
So it's really important to bear that in mind when we're using our diagnostic tests. So, when you, when you've got a diagnostic test that you want to use, what are you trying to detect? Is it the parasite itself?
Is it within the host? Are you likely to detect it in the stage that it's in? Is it pre-patent?
Is it likely to be there? And if the parasite's there, does it always cause disease? There are also environmental stages that you may not be able to detect, so bear that in mind where the infection is coming from.
And actually sometimes we detect parasites within the environment as well as the host. Indirect, tests look at host immune responses. So what is the predominant immune response or biochemical response, such as, release of biochemistry or liver enzymes.
And these responses, may stay around and not, be present when there's disease there. So, thinking about what are these host immune responses detecting. This will then influence what sample you need to collect, so thinking about where that parasite is or the stages of the parasite you're trying to detect, and what laboratory tests you might need to use.
Ultimately, you need to know how well that test performs. So this is the horrible thing that people start panicking about, the statistics behind these tests. So, thinking about the sensitivity and specificity.
And these values, all they mean are, is that how like, you know, what, does this test correctly classify the animals. So, sensitivity is the ability of the test to correctly classify an animal as positive, and specificity is to correct the, is the test's ability to correctly. An animal as negative.
Now, it's difficult to sometimes get that in your head and think about it. So quite often I think about the flip side of sensitivity being, what is the ability of the test to generate a false positive. So if you've got a high sensitivity, you're unlikely to get false negatives.
With specificity, if you've got a high, specificity, you're unlikely to get false positives. And remember, these two, values are interrelated. So if a test there's a high specificity.
It may have a lower sensitivity. If you increase that sensitivity, then specificity may reduce. These are not things that you would be expected to calculate and just bearing in mind that these factors is important, and you can bring up the sensitivity and specificity that I'll discuss in this lecture, but also look in published literature or look in laboratory data.
Positive predicted values you'll come across in the literature, and I'm not gonna go into these, and people do wonder why we don't use these because they give a probability of an animal being infected. They are potentially useful because it says, right, this animal is potentially infected or not infected, or a group of animals. However, you need to know the prevalence of disease within that population to work these out.
And therefore, this varies on farm and quite often these parasites are infecting a lot of animals to 100%. So, really, can we calculate the probability, of an animal being infected on an individual farm? No, not really, because it varies so much.
So these are not useful. So this slide is probably my main one that I'm trying to use as a take-home message that a high specific test means that they're, they're useful to rule out a diagnosis diagnosis, because there's very few false positives. A high sensitivity is useful to confirm a diagnosis because there's very few false negatives.
And that's how I would take into account the sensitivity and specificity. If you've got a high expected prevalence of disease on farm, that will improve the sensitivity and specificity to a certain extent. But bear in mind if you've got a low prevalence of disease, you may get false positives with any tests.
So always question when you get a positive result if you suspect that disease is low on farm. Other factors to consider are, if you're using multiple tests to confirm a disease, are you, likely to get agreement between the tests? Because agreement can occur through chance, alone.
If you're comparing apples and oranges, and that's what I mean is, are you comparing a direct test, such as a faecal worm counts, to a, indirect test such as an immune response, to a parasite. There may be a, a lagging development, development of an immune response compared to when the parasite site starts, shedding eggs. So actually, are you really going to be able to confirm disease, at, at different stages of the life cycle using different tests?
Pooled samples, is something else that, you need to consider when you're considering diagnostic test performance. They're convenient and cheap because you can collect a load of samples and think about, diagnose, disease or infection within a group of animals. But bear in mind that, it's a crude technique for detecting disease.
And it may dilute, the infection that you're trying to pick up. So if one animal is shedding a lot of, parasites and they're in fact very healthy, and the other animals are, shedding low numbers of parasites, this will average it out and give you a low, faecal worm egg count, for example, and it, that may mean that there isn't a problem on the farm. However, if you mix animals that we've got Clinical disease, with non-clinical disease, or non-clinical infections, and you get a kind of normal, faecal worm egg count, that's going to skew and give you a false negative results because you are, you're diluting, the eggs in the faeces.
So bear that in mind, when you're using these, full sample tests. The pool sample will also be affected by, sorry about that, be affected by the number of samples that you take. And it's worth bearing in mind that different tests, can detect disease within, different sample sizes.
So, for example, bulk milkylizers can often only detect, Disease in, a group of animals that are less than 300 animals, and they require around about 10 animals to be infected and releasing antibodies into the milk, for the cattle lung wormlizer, for it able to be detected. Other tests may detect fewer animals, and it's worth, estimating the performance of these tests, as you may get false negatives in these populations if only a few animals are infected. So thinking about these, routes of trying to select a diagnostic tests are important.
So, what are you trying to detect? What sample do you need to find the thing that you're trying to detect? What's laboratory method are you going to use?
What's the reliability of the test, as we've just been talking about? And then there's the practical aspects. How are you going to get these samples?
What's the cost of the test and the availability of the testing in your area? So, the next bit that I'm gonna talk about is the performance of the individual, rein diagnostic tests. And these are the specific tests that are available in most, UK, farm animal practise practises, whether that's in the practise itself, or you can send them off to, a laboratory, across the country.
What is available for nematodes, firstly, after you've taken a farm history, looks at the environment and the host population, the majority of these tests are available for both sheep and cattle populations, and there are direct tests and the indirect tests. The only one that we don't really have available for, sheep populations are immune responses, and that's something that we use in cattle herds quite frequently. I'm going to take into account these tests one by one and talk about the pros and cons of these tests in different circumstances.
But I'm gonna just remind you to take into account what is the reliability of these tests. There is no perfect test, no test is 100% specific and sensitive. But some of them are more specific and sensitive than others.
And it may vary depending on the stage of the parasite's infection, but also, the, the burden of the infection within the host. So it's worth bearing that in mind when you're, trying to, interpret test results. And then there's the practical aspects that we've already talked about.
So firstly, a kind of more direct test, I guess, is looking at clinical signs. So diagnosing using your clinical skills is equally a diagnostic test, as any of the laboratory tests. It's specific for individual diseases, which I won't go through, as you'll all be well versed on these different infections.
And often this is the first thing that the farmer detects on farm, in an outbreak situation where parasite control, is not very good. So it's worth trying to quantify this on farm, if this is the only data that you've got in an initial problem. On an individual level, you need to think about are the differential diagnoses as you might generate false positives, for such things as diarrhoea or weight loss.
You might also get false negative results. So just because you're not seeing outbreaks of disease, and what is the level of subclinical disease on the farm. And there are other ways of trying to detect subclinical disease, and that's why, where you might use, diagnostics to try and quantify the impact on these animals, such as weighing animals and estimating, daily live weight gain, etc.
From a population level, it's often used to identify animals to treat, which I'll come up, with later on. It quite, can quite often be reactive because this is the first presentation that farmers will see, and it can also be used to target the treat animals. And as I say, quantifying impact is really important with this.
So, you can look at, things like body condition scoring, which can be used to try and estimate the impact of parasites on farm, thinking about what stage you would expect, animals to have certain body condition scores in their production cycle. But you have to bear in mind that there has to be adequate nutrition to take these into account in an absence of other diseases, as this might generate false negative or false positive results. Another test that's based on clinical signs is the Formatia assay, which is basically a bit like, one of those score charts for how you like your tea, cups of tea made.
And it's, it's a colour guide looking at the level of anaemia and trying to quantify the impacts of anaemia within, sheep in particular or goats. You compare the, colour chart to the mucous membrane of the eye, in the sheep or the goats, because that's the most sensitive and specific area. And it's useful to identify primarily he monosis.
So if you've had an outbreak of hemonosis or you suspect it's present on farm, particularly in warmer southern areas of the UK, you can use it to try and quantify the number of animals clinically affected. There has to be absence of other disease such as fasciosis as this can generate false positive results. And it can be used in control programmes to target leastelect treatments.
But you have to have absence of other diseases, to try and, identify animals to treat. Moving on, other kind of, direct tests, look at the clinical pathology, and these are things that we don't really tend to recommend using, because they don't perform very well in populations of animals, albeit bar a few of them. We can use PCV to quantify anaemia as any kind of helminth burden will generate anaemia.
And if you notice a lot of animals in the abattoir that look anaemic, or you have animals on a clinical exam that look anaemic, then this might indicate that there's a high level of paracetemia, compared with other kinds of, clinical exams and how the animal, looks when you, have them for weighing. Eosinophils, some people will use it to identify or try and rule in parasitic disease in ruminants. However, it's not very common in the blood.
It's more localised when you diagnose eosinophil, so I wouldn't tend to use that, at all. Biochemistry, when we're looking at that, we can use total protein, urea to identify protein loss. And this can be useful actually in populations of animals, When we have, an outbreak of, anaemia due to fasciosis, for example, and we can identify that there may be a problem going on when we're conducting metabolic profiles with chronic fasciosis, in the winter months.
So it can be useful and it can be a cheap test to conduct if you're doing other kinds of metabolic testing. With most of those, you need to think about differential diagnosis for false false positives and whether subclinical disease will actually cause these problems to occur. The only one that we kind of use on a kind of population level in cattle is testing for Pepsinogen.
Pepydoin is something that is, elevated with, osteotagiosis, and it's because, of the L3 stages affecting the parietal glands in the Abemazin. And basically, this is just because the, L3 develops to the L5 and damages, these, parietal cells, releasing, Pepsinogen into the blood, which can be detected and quantified. So the animal has to have this stage and reactive parietal glands to be able to detect the parasite in this waste.
So if you have an animal that is latently infected, you're not going to get Pepsin Pepsinogen released into the blood, for example, in the winter months. However, if these L3, L5, sorry, burst out of these parietal cells, when we get into the spring months, or in the summer months during grazing, when the animal is initially being exposed, you may be able to detect disease if you're detecting these parasites bursting out. So you need to think about what time of year you might be using this test.
So, it can be quantitative, and the more, parasites that are bursting out, the parietal cells will give you a higher response. So it gives you a likelihood of detecting disease. So it's very accurate in both individual animals and populations of animals when you're using blood sampling techniques.
It helps identify animals with clinical disease really and sub subclinical disease, and depending on when you take the blood sample. It can be useful for targeted selective treatments, so identifying which animals do you need to treat, and this is potentially identified when you're sampling animals, and when you're weighing them. And you can pull blood samples, for monitoring purposes at certain times of the year, such as the summer months.
As remember, in older animals, Pepsinogens will be raised in these animals because, they will be getting infected, but they'll have developed immunity. So, it's always worth bearing in mind the parasite biology when using, the Pepsinogen test. Serology, I'll just briefly touch upon.
It's not usually used in individual animals, and it's only useful with certain parasites such as Austratasia, fasciolipatica, Neospora, and Dixiacoruss, the lung worm. Individual animals, it's often not useful, because a lot of animals are already exposed to these parasites, but it might be useful in an outbreak, if, if a parasite hasn't been detected on the farm before, such as osteola or Neaspora or Diyallis. You can monitor the effects on production, particularly with the ostratasia, Eliza, which can be used on bulk milk samples, and it's estimated, the level of, positivity on the Eliza might impact the levels of production.
And this, reference here does discuss how you can use the levels to, estimate the impact on young stock in particular that, that are contributing to the bulk milk tank. This might help you target treatments at certain times of year, and it might also be able to estimate treatment efficacy. However, you need to bear in mind that some of the cons of this are that how long are these antibodies hanging around for when parasites have been exposed, animals have been exposed to these parasites.
For example, if an animal's been exposed, to fatile hepatica, the antibodies tend to persist around for the lifetime of that animal. Whereas with dittycolis, they last around 4 to 7 months. So it can be useful for estimating, dittycorlis in different grazing seasons, but fasciola is probably unlikely if the parasite is endemic on farm.
For faecal worm, egg counts, is our next kind of, direct test that we can look at. And they're the most commonly used diagnostics in ruminants, looking at primarily the gastrointestinal nematodes, and it's basically where we detect these eggs that look very similar from various different trichlo tri trichostrola species, in the faeces of ruminants. It only detects, the presence of eggs.
It does not necessarily quantify the burden, of that infection. And that's basically because, the variability, of the different parasite species that are infecting, these animals might release different numbers of eggs. Also, different animals have different levels of burden, and that's something that Just talk about, in a moment.
So it's really worth bearing in mind, you need to bear, bear in mind that an animal shedding nematode eggs is not necessarily, being suffer, is suffering disease because it may have, developed immunity to these parasites. So we use, these tests to sample sample individual animals and populations of animals, to detect clinical disease. We also, tend to use it to check efficacy of implemented treatments, and select, animals that are resilient to nematodes and breeding those that are, resilient to nematodes.
So when we're sampling these individual animals, we need to bear in mind is this animal likely to develop immunity to these parasites and in fact shedding different numbers of parasites in their faeces because they're immune and that's normal for them. There's a variability in faecal output, particularly in diff in, cattle species where the faeces are, dilute. So bear that in mind when you're taking these samples, that you may in fact get a low, results, if you've got dilute diarrheic faeces or in stages where the parasite, the animal hasn't developed adult stages yet.
There's also worth bearing in mind that different parasites, in the GI tract shed different numbers of eggs, so that they have different fecundity, basically. So homonchous species, a single, homoncu adult will shed, hundreds of thousands of eggs per day, whereas tricus strongile species will only shed a few hundreds to a few 1000. So, we cannot necessarily rely on the numbers of eggs in every animal to identify that it's been clinically affected and you need to com combine this with clinical science.
We're often trying to use this to estimate disease in a population of animals to see if it's affecting the animals as a group. And we often recommend pooling, samples from 10 individual animals, and wrapping those samples up, as individuals and pooling it. It's an average from that group, so bear in mind some animals will shed lots of, lots of parasite eggs than others, and there is a need for a repeat testing as parasite populations are in flux throughout the season.
The principle, I think most of you will be aware of, you're collecting the samples and basically trying to get, trying to, consolidate the eggs into an area that you can detect them. And because these eggs are small, they will float in salt solution. The results can be quantitative or qualitative, so that means we can count the numbers of eggs to determine whether it's having a clinical effect, or if we identify certain eggs, we can say that's definitely causing disease.
And when you are doing pooled samples, make sure you proportionally mix these samples. So I mentioned here that you're taking 2 grammes of faeces of, to, using this kind of flotation method. Here, you can, you can see a McMaster method being used.
And when you're doing these pooled samples, make sure you add the same proportion, from each animal into the pooled sample to then then put into your McMaster slide. Each egg, that you detect, in your McMaster, is 50 eggs per gramme, and there are other methods that you can use such as the cuvet method, but they're all very similar when you use them. This is very cheap and easy to conduct in practise, and there are other field methods that you can use, that I've described here.
And if you're interested in them, I've highlighted them in the notes section. And they basically just speed up the process, such as the float tech method, you don't need lots, lots of different pieces of equipment. You can just match the pieces in this device that can be seen on the left there.
There are also portable bits of equipment that you can use on farm, which might engage farmers because you can show them the parasite, down the microscope and get them, used to doing this themselves if it does save them money. But there does need to be a veterinary intervention to discuss what these results mean because just detection of these, eggs does not mean that these animals need treating or that they're in fact affecting them. And other tests are available and you can send these samples to the laboratory if it's something that you maybe don't want to conduct in your practise.
When we get these results, we can use quantitative results, to identify the different eggs. It's worth bearing in mind they all look very similar, so we can't identify specific infections such as hemonous through this method, but we can identify a kind of general gastrointestinal nematode burden. Which we can kind of, compare to whether the animal's clinically affected or not.
In some instances, instances, it's qualitative, so, eggs are there that definitely cause disease. So if you're detecting pneumattoyrus batters in a young animal with diarrhoea, it is very likely to be causing disease. So seeing any of these eggs at all will imply that you need to, treat the animals.
So that's worth bearing in mind too. Talking about the quantitative interpretation that I've briefly touched upon, the degree of infestation, . Cannot be estimated, through, these faecal worm counts, it's only can be suggestive of that.
So, you must interpret with farm history, the species present, so you might identify fine through postmortems or larval counts. And if you don't do that, that's fine, but just bear in mind that you can't ultimately say that you've got, you know, 100, a few 100 eggs per gramme that these animals are definitely causing. These animals definitely have clinical disease.
And mixed infections, you can use these as a kind of guide, these, rages of eggs per gramme in these animals. Just to kind of highlight this, if you have a high faecal worm egg count in certain populations, such as, hill populations of sheep, you can have faecal worm egg counts that are thousands of eggs per gramme, and this might indicate heavy infections if you just take the numbers that are displayed here. But if you think about it, when you've got, hill sheep, you have a, you have a low stocking density.
So therefore, parasite infections like to dilute, and therefore, there isn't a high infection pressure on pasture. So even though animals are shedding lots of eggs into, into the, environment that might be picked up from lambs, they're unlikely to encounter them because the, it's diluted on the vast pasture that you've got. It may be that you've got no adverse signs of clinical disease.
So these animals might be resistant and resilient to this disease by, being exposed to small infection doses. So, just because there's a few 1000 parasites there, look at the animals, see if they're actually clinically affected, and get your hands on their body condition score. And this will influence your antthalmitic practises.
So, if an, if an owner is using a lot of antalmitic on the farm because of these high faecal w head counts, is that actually needed? And it might be suitable to look at, if this, Block has got ampletic resistance in it. You can use these faecal worm gg counts in healthy adult animals to try and select for animals that are, resilient, to, parasitic infections.
But just bear in mind about the other reasons for selecting these animals. Are they infected with other diseases? Have they got good confirmation, etc.
But, you know, using these faecal worm counts can be useful for selection of animals. And just bear in mind that the context of the samples, so if you're using these faecal worm counts in older animals, they're less likely to demonstrate whether the animal's got clinical disease or not, because often older animals are immune to these parasites. So this is what we've mainly talked about, the kind of pros and cons of these tests, why we get false positives and false negatives.
The sensitivity of these tests, tend to be, around about 50 eggs per gramme. So you cannot say any samples are negative if you don't detect any, eggs at all. It's worth bearing in mind that if you keep the faeces, even in a fringe for more than 4 days, the eggs might hatch and you'll get false negatives.
And again, mentioning, thinking about the stage of parasite presence, the species of parasites that may be present if you're unsure, and if, the faeces are dilute or watery. Another method that's not commonly used is detecting larval stages, from hatching the eggs to determine what species are there. And this can be important if we're looking into resistance run from insects on the farm.
Often it's used, as a primary diagnostic method for cattle lung worm, but otherwise it tends to be an academic exercise. But in the future, we might be able to molecular speciate these, larvae that are hatched out in the faeces, to determine, the levels of amphlegmytic resistance in these, nematode populations. So for the lung worm parasites, you can use the bamin assay to diagnose, sensitivity, sorry, to diagnose, the presence of cattle lung worm in the faeces.
But just bear in mind that, this test can have a lot of false negative results. So very few false positives because the larvae look. There isn't any other larvae that look like, this parasites, but you might end up with pre-patent stages which haven't got larvae in the faeces, despite clinical coughing.
You can have reinfection syndrome where you get a negative because the animal, has got, damage to the lung tissue and the eggs are not being released. And also, you might detect low parasite numbers when you've got mild disease. However, this might be not something that you'd want to treat, because the animal will be developing immunity, to this problem.
So you use this testing combinations of clinical signs to really confirm diagnosis rather than just using it as a surveillance tool. Copperculture, as I've mentioned, can be used to diagnose a specific nematode species, in the guts of, Both, cattle and sheep. It's often used if we're looking for resistant nematodes and trying to decide what species are present.
The technique briefly is by, you basically put the faeces in a kind of greenhouse, for two weeks to get the eggs to hatch, and you then can identify the larvae under a microscope, using this method that's described in, the reference that I've displayed here. It is time consuming because it does take up to 2 weeks for the parasites to hatch and develop. And it does take a lot of skill, to kind of look at these parasites.
So, although this is, can be used in trying to detect something into resistance by isolating parasites to, assess their genetics through, Larval stages, it isn't really used in practise, but it might be something that is used in future to investigate resistant profiles in gastrointestinal nematodes. Postmortem, they are useful for detecting disease, but you just need to bear in mind, is this animal that's died or that you've killed is representative of what's going on on the farm. If it's a particularly sickly animal, is it likely to give you an impression of what's going on on farm?
And so think about why you're using this test. Is it to confirm disease or is it to, try and estimate what's going on in the whole population? Think about where the parasites are, where you're going to look for them, and specific parasites in different locations.
And this is particularly important with gut worms. Gut worms, you can also count and give a score, for the number of worms, and this is where you directly estimate burden, and it can give you a relative idea of the impacts on this individual animal and might be able help you to estimate the ongoing losses in these animals. So it's worthwhile knowing, about the different stages of the parasite and when you're going to see these different stages of disease.
So these are a few examples with the guts, nematode in sheep, for example, with, T circumcincta, because it's in the Amazon, that's where you look for it, essentially. And you might see swirling movements within the digester, when there's lots of parasites. Although you might not see many if there isn't a large burden, but that's what we're really interested if there is a large burden.
Hemonus and tortoise, we can see that because it looks like a barber's pill worm like you can see on the side of the alma here. And other parasites in the small intestines such as mbattis look like cotton wool. And so you can see these things on gross PM and I think this is something that is underused in practise to identify parasitic disease.
And you can do these, worm counts yourself, by kind of just sieving through that digestive material and using a bit of dilute eye. In a kind of white tray to try and count the, parasites. Although this is probably quite time consuming in practise, if you send an animal for postmortem quite often, a lot of the laboratories in the UK will do this for you, and it can be useful to understand, what's been going on in that individual animal.
So moving on to the fluke tests, we have a variety of tests and it's really worth bearing in mind the stage of infection that you're trying to detect these responses. And this diagram displays here that you're trying to have a look at where the juvenile or the adult species are in the life cycle, so it's worth bearing that in mind. Again, we can use haematology and biochemistry to look at these tests, however, they're often only used in individual animals, and there are a lot of false, kind of positive results because they're, you have to consider different stages of infection.
In individual animals, we might use, the liver enzymes, however, they are relatively short-lived. For example, GGT, which can, be detected in, adults, adult infections, in chronic infections, is only released when there's presence of adults. And GLDH, doesn't last very long.
It's, it's around about, 14 hours in cattle, so in, in bile duct migrations, so it's worth bearing that in mind. If you've got chronic disease, you're not going to detect that. Again, albumin can be used, and protein levels like I've talked about in metabolic profiling to try and estimate if flu, chronic flu contaminant in fact in flux.
And remember, exposure with serologies is not necessarily imply active infections, so it's only really useful if you are trying to investigate a primary outbreak. Flute sedimentation, is one that's primarily used in practise, and we're looking for eggs in the faeces, and adult fossil shed lots of eggs. We need to use a sedimentation technique because the eggs are big and they look very different compared with nematode parasites.
We rarely get false positives, other than if we've got rumen fluke present, which of which doesn't often cause disease unless it's in large numbers in young animals. So, the difference between them is worth bearing in mind where foci the eggs are yellow and, rumen flute species are clear. False negatives can can occur in acute vasculosis where you've only got acute disease in juveniles present.
Chronic fasciosis where the bile ducts are calcified and you've got very few adults present. So you've got clinical disease because the liver's damaged, but very few adults present. And fluctuation in egg numbers is important to bear in mind.
The bile duct sheds them intermittently and cattle, which have diarrhoea can dilute the faeces. The copper antigen, I say, is a is a limited use currently, but it's very useful to diagnose infection as it's basically detecting the antigen in the faeces of animals. It's excreted into the faeces from parasites that are present in active infections.
And it's useful to detect late-stage juveniles and adults. It's detected by LISA, so there are very few false negatives, only in very low levels of disease, but they can fluctuate from day to day. So it's sometimes worth, repeating if you think you want to confirm disease.
And false positives, if you've already treated, for the parasites within 7 days post infection. I've mentioned postmortem previously, it's useful in outbreaks or sudden disease or real thrift, and it's also useful to quantify, slaughterhouse status to identify impacts of disease. And it can be useful to try and investigate and get the farmer to try and look into some clinical losses.
This study here, kind of just demonstrates the performance of the different tests, within, cattle, at a slaughterhouse. Around about 650 cattle were slaughtered in this study, and we were comparing the different types of, diagnostic tests here, such as necroscopy, meat inspection, the copper antigenalizer, and faecal worm egg counts and serology at different stages of infection. The main take home messages here are, if you are using postmortem, to try and diagnose disease, if it's just quickly looking in the bile ducts, the test doesn't perform as well, and you may get false negatives in low burdens.
So if you do detailed necroscopy, where you're looking at every centimetre of the liver, you get, a high, specificity, so fewer false positives. Or false negatives. The blue here is looking at, the faecal, worm and count sedimentation tests, and it's worth bearing in mind that this varies throughout the year.
So if you've got adult parasites present, you will have a higher sensitivity and fewer false negatives. If it's in, in acute stages of disease or when animals have got low levels of infection, you are gonna get, you are more likely to get false negatives as it can be seen here. It's also worth bearing in mind that actually, the copper antigenolyzer performed very well in this study, and it was relatively consistent.
So it's maybe something that is an underutilised test in cattle populations, because there are very few false positives, and also, the false negative result is, relatively consistent. So finally, I'm briefly gonna talk about, trying to assess the different priorities, when you're considering whether to control disease on farm. Apologies, I'm going a little bit over time here, so I'll just try and quickly go through these.
So considering why we're using a diagnostic, it might be depending on the clinical priority, production, economic priority, or the preventative priority. And this will influence when you're trying to select different diagnostic tests on the farm. This table just looks at, for different stages of cattle diseases, that are of major importance when you might use different tests.
So think about what stage of infection have you got, what, stage of the parasite you're trying to detect, and what is the, the impact that you're trying to detect in these animals, and that will help you, to you to select the different diagnostic tests and when they might be appropriate for use. So specifically looking at clinical threshold, so you've got clinical disease in this farm, and it's often the first thing that the farmers attacks. So thinking about when these clinical signs occur at different times of the year, the stage of the life cycle, the time of year, and environmental factors will affect that.
And there are sources of information that we can use to try and get an idea of when these diseases are likely, such as from, our basic knowledge of these diseases is just, is shown in this plot here, that certain parasites are more prevalent at certain times of the year than others. We also get trends of data to monitoring, through, the SAC, and, the APHA and NARDIS use these, this data to be produced from clinical outbreaks throughout the previous years. So we can look at this data and see that PG, for example, is very predictable throughout the, Each year the, the risk of disease is very, there's very little variation.
Whereas with, lung worm or husk in cattle, we have an increase in the past few years of husk. So this may be something that we need to look out more for. And the same with fascilosis that we are having an increase across, parasite populations.
So it's worth bearing in mind that we need to look for these diseases more frequently. There are more specific ways of forecasting for these diseases, and with increasing, technology availability than we can predict when these, parasites are occurring in the in the areas that we, conduct our practise. So there are general press warnings in the vet record, Farmers Weekly, and that might be through people reporting disease, or the time of year that we expect disease to occur.
So these things might alert farmers to when there might be diseases occurring. But there's also more specific risk forecasting where, mathematical models are used to predict disease through submission of clinical samples, to, to aid statistical models to predict disease. And these are available for liver fluke across both cattle and sheep.
And we have specific parasites that are predicted through this in sheep and cattle. And if, if you take Nematodiris as an example, through the SOPs website and the APHA website, we've got this kind of risk map. So you can look up on the, website to see that, that there is more disease in your area and warn farmers, that there may be disease present.
Nardis have also produced a similar kind of risk map that you can look at specific areas to detect disease. So, we can also, think about our parasite biology, how often we're likely to get disease. So if we take a lowlands sheep flock and we're looking for specific disease, we know that, the perippos shouldn't rise, it occurs at, between the kind of spring months, before lambing occurs.
Lambing starts and uses with chins and triplets could be dosed at turnout. We then get the lambs starting to graze and we get an increase in parasites being multiplied in these populations. So should we be expecting disease at this time of year because the parasites are increasing on pasture?
So should we really be sampling these animals throughout these three week life cycles that we've got displayed here? Well, this is dependent on the parasite biology, and the farming system that we're, in. So what are the grazing practises, what are the stocking densities?
What are the groups at risk? Is it lambs, that are particularly at risk in certain groups? What are the previous control and and minted practises on farm?
And when can we actually sample? So, when are the, when is the farmer actually, collecting animals on farm? So using the example, that is, that I've currently encountered in practise, we have a lowland flock here that's that, use a lambing on permanent pasture.
And we've got a, we've got 5 different groups that are lambing, and we've got a kind of relatively high stocking density here with a high lambing percentage. Rotational grazing is used, but the pasture is poached, so there is a lot of kind of stocking density here and exposure to parasites. Ad hoc treatments are used by this farmer, with the benzo midazole given in May and various unplemented treatments given throughout the year depending on faecal where counts, and only lambs are weighed at finishing.
So this year we had an outbreak of scouring these lambs, so suspecting that there was clinical disease on this farm. So differentials were thought about with pneumattodirus batters, PG and coccidiosis. So we did conduct, faecal worme counts on a group of lambs, considering the risk map here that it was likely in our area, that nematodiris was present.
So, What we, what we ended up with was a faecal worm count conducted it within the five groups because it's important that they're all managed differently. And what we actually ended up with was Nematodiris was present. So we've confirmed disease in these animals.
We've then got one group that has a relatively high, trich strongile count, so should we do something different in that group. So the plan was to use benzomidazoles in all animals because we identified this clinical disease. But it's worth checking, whether these, drenching treatments are working because, we do have a high triker strongile count here, so there might be evidence of resistance.
Discussing resampling and weighing in futures to try and estimate whether disease is having an impact across that farm. So moving on to pre-production economic thresholds, thinking about, fasciola in particular, we can assess the clinical losses, production losses and associated losses and trying to estimate whether there's a big enough impact to instigate, production and, economic losses on this farm and whether we should investigate it. But how do we estimate the cost of parasitic infections to try and convince the farmers to do something?
From industry or scientific literature on individual farms, for example. So, we've got, these production estimates that we can look at from Ebles, or, or, scientific literature here that can be used. And I've generated this table that you've got in your, notes here to try and give you estimates to kind of briefly quantify what's going on in animals and how parasites are in, causing an impact.
We can also do it for specific farms because certain parasites will have more of an impact on different farms. So, firstly, we can, tar, we can estimate the effects of implemented treatment just by estimating daily live weight gain quite simply by weighing these animals if it's possible. And you can benchmark this against the average, across the industry.
You can then record this throughout the years and estimate if your control practises are having an effect. And you can also use it to target the selected treat and not treat animals. There's also these online calculators that can be used to estimate the impacts on specific farms, and you plug in a few numbers that you can gather from the farm, such as, how much anthem is being used on farm, what the production impacts.
And these websites can generate a kind of estimate of the amount of money that's being lost with these parasites on the farm. And I'd recommend using these if you're, trying to convince a farmer to, apply, treatments or review their current control practises. So if we're thinking about it from a Liver fleet perspective, there are various methods of surveillance that we can use and certain ones of these are more important for certain disease presentations which we've already gone through.
So using an example that I've, recently encountered in practise, we had a beef suckler client that had, fastening bullocks at 16 to 18 months of age post-weaning, and there were abattoir reports of disease. Faecal worm egg counts we used, housing to look at PGE, and also, we treated, with targeted selected treatments to try and get rid of MPG lice and liver fluke. However, it's always really important to estimate is this treatment actually having an effect, because this recent study showed that just by blanket treating these animals with antthalmitic housing, doesn't necessarily mean you need to, because certain farms will have Require and treatments and others weren't.
So it's always useful to try and estimate daily live weight gain after you give these treatments and to those animals that you haven't given treatments, because then you can estimate whether actually using this treatment and it's having a production or economic impact on this farm system. And it can be useful for future targeted selective treatment if you are using weighing and daily life weight gain measurements. And finally, I'll briefly just work through in the next kind of 5, 10 minutes, so apologies I'm going over a little bit here.
But just looking at the preventative threshold. So using an example, we had a lowland flock here, that's, is fairly typical of the area that animals are on a permanent pasture, in a large co grazed area with deer. Lambing percentage was relatively high, so relatively high stocking density, and ad hoc ample minted treatments were used.
No faecal worm egg counts were performed, and it was unclear if the previous antheminted resistance on the farm. Lambs were weighed at finishing for 40 kg, but a proportion of lambs had low daily wild live weight gains and scour noted in these animals. So how do we approach this clinical problem to try and prevent this impact in future?
So how do we approach this problem of anthemytic resistance, which, is an inevitable gene selection towards onphlegmytic resistance when you're using, antalytics because you're trying to eliminate parasites, and you're left with the ones that are resistant. So it's dependent on the composition, size of refugia populations, stocking densities, and the frequency of analytic use. So again, reviewing, that history on farm is really important.
And development of antalytic resistance develops over time. So it's something we need to, estimate and review constantly throughout the year. And remember, antalytic resistance is inevitable over the years.
So the more you use antalytic treatments, the more, like, the more of a resistant population will be in refugia, and you will have a analytic resistance problem, even if it's not detected. So why do we need to diagnose? Maybe there's initial status on farm that we're not sure of, or to monitor if antilimited treatments are working, or to continuously monitor if they are, having an impact.
So if you detect a clinical a case of antalmitic resistance to antiment treatments are not working, the efficacy of the antalytic is less than 80%. Whereas if we're using diagnostics, we can detect it before it has a clinical impact, at less than 95% efficacy. And the way we do this is through faecal worm egg counts.
So, a drench check, for example, is checking the efficacy after treatment. So simply doing a faecal worm egg count 7 to 14 days after treatment to check if there are no eggs present. Faecal worm egg count reduction tests can be used where we quantify, faecal egg count beforehand and then assessing it after treatment again at 7 to 14 days.
And this can estimate the, Quantity of unflammed resistance within our population and estimate if we need to hurry up and do something about it. Other diagnostics will be available in future, and these will be coming available in, future years. It's also worth bearing in mind the differentials from filming resistance.
Are we using the appropriate, products at certain times of year? Is the, product stored properly? Isn't it, is it working?
Is it left out in the sun, for example, or has it been used the previous year and it's gone out of date? Is a dose of antalmitic being used properly, so are we weighing these animals, are we checking dosing guns are working, etc. And are we having rapid reinfection in a high challenge setting?
And this is maybe where you are having high stocking densities and you're not getting control of the infection. So coming back to our flock, the way that we looked into this at the June dose and we got on farm and weighed the animals to estimate daily live weight gain to see if it actually had a clinical impact. We estimated if we needed to use as much anthem in it because some animals may or may not need treating because their daily live weight gains are normal.
And we collected samples for a faecal leg count reduction test at this point. And then we gave, the farmer options about what to do next, because remember, this is in partnership with the farmer about how we control treatments. And being on farm and engaging through these diagnostics is really useful.
And using these cheat tests is really helpful to get you on farm. So we gave options of using faecal w egg counts, for targeted treatment at certain times of year, as a group treatment or a targeted selected treatment approach, if we could use scales on individual animals through, electronic ID tagging. And with collaboration with the farmer, we could, we could design a health plan.
So you might not be able to instigate the, frequent, frequent counts in the first year that you're trying to control disease, but you can try and quantify disease. So, you know, setting the bar low initially and then building up, as you go along to try and control onhement, anthemments, use on farm. So, in summary, there is no one size fits all approach, as I've kind of talked about and rapidly gone through, that you need to estimate why you're doing these di using these diagnostics on farm and why you're approaching the clinical problem.
And that will help you determine how you, use the tests and how you might instigate control practises. Choosing a diagnostic relative to the sample size that you need and the performance of the diagnostic tests, and you can use this to formulate a holistic health plan on the farm, with the farmer. And using these resources, here, are very useful to kind of review how these parasites, are kind of transmitted on farm, and also, possibilities for control practises on farm.
So thank you very much for listening to my lecture, and bearing with me, and if you've got any questions, I'm more than happy to answer them both after this, seminar or, through the email that I've got on here. Thank you very much. Fantastic, thank you very much for that, Rob, and I er I get the impression that you could have easily done a hour's presentation on just one of those elements, of mind trying to fit in a number of them, no mean feat is it at all?
No, not at all, so apologies that I rapidly went through that, but . Yeah, it's, it's something that is quite complicated, but, if you use the notes that it's the main points are covered there as well. So, and I'm more than happy to discuss any queries that people might have.
Fantastic, thank you very much. So, please do, we do have a little bit of time for some questions, so please do. Put any questions down and I'll, put them to Rob.
It's always a great sign of a good presentation when we have, the participants continuing through to the end and we don't have any drop offs. So, obviously they were enraptured by you, Rob, and, please, so we'll just see if any questions come in shortly. Just a bit of housekeeping, obviously after this webinar, a, Little survey monkey will, feedback form will pop up in your browser.
Please do take your time just to complete that. It's only a couple of questions, but it is really useful one for ourselves, but also I know our speakers also like to receive the feedback as well. So please do take some time to complete that.
So just seeing if we have any questions. It looks like, to be honest, Rob, that you're being let off scot-free today. So what, what I will say obviously is this webinar has been recorded.
It will be up on our website within the next 48 hours. So you will be able to obviously refer back to this webinar at any point just by logging in and accessing it through the webinar vets website. Rob has kindly put his details there, so if you do have any questions, obviously you can contact Rob directly, and I'm sure that he will be, as he's already said, he'll be happy to, respond to any individual queries you may have.
Oh, just before I was about to wrap up and someone's pop on in. So let's see what John has to say. Super useful presentation as we're in the midst of our hemoncus, is it?
Yes, well done. Yeah, thank you. Peak season in New Jersey, especially the way to conduct with farmers is a great way to spend our Independence Day here watching it.
Thank you, John. So, yes, happy Independence Day, John. Absolutely, absolutely.
It's the thing I did there cross my mind because I've got an American friend myself, so I have wished them happy, Independence Day today. So a great feedback. Thank you very much for that and .
It's interesting obviously that there's transferable aspects from the UK over to er America. Absolutely, yeah, absolutely, and. Yeah, and I think that's, that's the importance of these parasites across the globe, really.
So, yeah, anyone that has any questions later on, just, ping me an email. I'm more than happily answer, if I can. Fantastic.
So, thank you very much for that, John. And you can go and complete your celebrations now. So if there's no more questions, all that, leaves me to do is to thank Dawn, who has been online as well this evening, assisting with any queries.
And also of course thank you to Rob for the fantastic webinar this evening. And I look forward to welcoming you all to our webinar very soon. So enjoy the rest of the evening.
Good night.