So, hi, everyone. Today I'm gonna talk to you about antimicrobial resistance on farms, and what we know about it so far, and what the evidence base behind it is. So just gonna, give you an idea of what I'll be covering today, and that includes why are we interested in the drivers of antimicrobial resistance on Farms.

What do we know about the dissemination of antimicrobial resistance from livestock and farms to humans? How might antimicrobial resistance develop on farms, and what is the evidence available about risk factors for antimicrobial resistance on farms? So just a quick introduction to myself.

My name's Andrea. I work as a first opinion practise vet for Langford Vets, which is associated with the University of Bristol. I did a residency here from 2014 to 2018, studying towards European College diploma in bovine Health Management.

And in doing that, I gained an awareness of evidence-based medicine and did a research project looking at the reduction of high priority, critically important antimicrobials on dairy farms. And that was the start really of my interest in antibiotic resistance, on farms and antibiotic use on farms. Now, this, slide of smiley, happy people is, just to, show you that I really am, supported by a big team of, of people here at the University of Bristol.

And they, are really the people who have shown me and taught me what I know, really. So, they are, really researchers at the forefront of the of research and antibiotic resistance on farms and in livestock systems. And a lot of what I know is from just being fortunate enough to be in the room with them, and in meetings with them, and in conversations with them.

So, hopefully, what I'll manage to do today is distil some of the information that I have gained from them, and, you know, make it interesting and relevant to you guys and me, out on farms. So Why have I decided to do a presentation about antibiotic resistance on farms? Well, I've been asking myself that a couple of times I was putting together this, .

Webinar, but ultimately, it's because I like to know the evidence behind the medicine that I practise on farms and the advice that I give to farmers. And increasingly, we have guidelines and targets associated with the use of antimicrobials on farms, or that are associated with reducing antibiotic resistance. On farms.

So, we've been asked to reduce the, use of high priority, critically important antibiotics on farms. We've been asked to advise against waste milk feeding to calves. Maybe it's just because I'm sad, but I like to know the evidence behind these guidelines.

And I think increasingly, farmers want to know about the evidence, too. And one thing that we have learned this this year is that, unfortunately, for the politicians, policymakers, and scientists alike, the science isn't always black and white. And the body of evidence changes over time and is never really complete.

And that's definitely true of antibiotic resistance. And I realised that before I got involved with the research here at Bristol University, I wasn't really aware of what research is being done into antibiotic resistance on farms. And, in fact, you know, I sort of knew it was there and knew it was on the farm, but I didn't really have any concept of how it might get there, how it might change, what kind of factors might influence that.

So my aim today is to give you a pretty brief guided tour through just really a handful of papers in the area looking at antibiotic risk, sorry, risk of antibiotic resistance on farms. I'm gonna focus mostly on dairy farms. And hope that at the end of the webinar, you'll feel you've got a bit more of an understanding of what types of antibiotic resistance are being researched, what the evidence is for, risk factors for antibiotic resistance on farms.

And then hopefully, you can have some better understanding and to be able to just have these conversations with a bit more confidence when you're out and about with your clients. I'm afraid if you're hoping to come away from this with a definitive answer of what will reduce antibiotic resistance on farms or in livestock, it's not really that simple. And, I'm afraid I probably won't be able to give you the answer today.

But I don't think that's the only reason we're interested in this. I, and I hope that, you'll gain some knowledge to be able to just understand more about what we do know, and maybe more pertinently the uncertainties that exist around this kind of area of research. So, firstly, on to, oops.

Moving on. Firstly, the importance of antimicrobial resistance. So, this, is an image from the O'Neill report published in 2016.

And although the report doesn't mention or include the threat of coronavirus in its stats, it's clear that the predicted risk of antimicrobial resistance to human health by 2050 will be the biggest cause of human deaths by that point in time, surpassing even cancer. So antibiotic risk is going to be a huge challenge facing human medicine going forwards, but what does, antibiotic risk distance in livestock and on farms have to do with the challenge in humans? Well, of course, there's an obvious link between the use of antibiotics in humans and antibiotic resist, resistance development.

But there's also much wider, reaching and complicating interactions that could affect antibiotic resistance in humans. So, for example, the use of antibiotics in, in, companion animals and in livestock. Most, one method of transmission there is, obviously, through meat and milk and food products, but also, a big possibility is the transmission through the environment as well.

And I think that, is likely to play its part in something that we As vets should also be aware of. So, the question is, if we know that resistant bacteria are in the livestock populations, how likely is it to transmit to human populations? So this graphic comes from some work in the Netherlands, looking at the transmission of different strains of E.

Coli from livestock to humans. And as you can see, there are different strains of E. Coli depicted by different colours on the graphic.

And, and you can also see that similar strains of E. Coli are found being carried by farmers that work with certain populations of, farm species. And actually, the general population have E.

Coli strains that are similar to other human populations, and those that are found in sewage and waste water. So, it suggests that if you work closely And, and live closely with livestock species. You will share that bacteria and will, likely share that resistant bacteria as well.

And, of course, all of us that work in agriculture also live in general population, are gonna end up in the hospitals, gonna end up in, schools, and etc. Etc. So we will be sharing those resistant bacteria as well.

So this is a quote from a systematic review which asks, do human extraintestinal E. Coli infections resistant to expanded spectrum cephalosporins originate from food producing animals? And the review found that there is evidence that proportion of human extraintestinal E.

Coli infections originate from food producing animals. So, there is evidence of transmission of resistance from livestock to humans, and these infections going on to cause disease. So, obviously, we have a role, as vets, to be acting to reduce the use of, antimicrobials and on the back.

Of these various, studies, we've been asked to reduce the use of antimicrobials, particularly the high priority, critically important antimicrobials. These targets are laid out in the most recent UK UK 5-year, action plan, which includes a target to reduce the use of antibiotic use in the treatment of food producing animals by 25%. And I'm sure most, if not all of you are aware of the industry initiatives set out.

In 2018, which, really aimed to almost eliminate the use of the high priority critically important antimicrobials on dairy farms. And as a profession, we've really made great inroads into reducing the use of antimicrobials in livestock species, both total and the high priority critically important. As you can see from these figures from the 2019 VARS report.

So, that is the veterinary antimicrobial resistance and cell surveillance report from 2019. And, and you can see here, overall, you've got reduction in total sales of antimicrobials, Alone and in Ms per kg and also reduction in the sale of high priority critically important antimicrobials. So The question then, really, is, if we're reducing the antimicrobial use on our, on our livestock farms, does it actually affect resistance?

So, this, is, a, a figure taken from, another systematic review that was funded by the World Health organisation. It's published in The Lancet Plant Health, which is an open access journal. And it looked at interventions, intervention studies, both in human and animal populations.

So, 82, studies describing resistance outcomes in animals, and 13 describing antibiotic resistance outcomes in humans. And it looked at the associated antibiotic resistance in those populations. So, these are forest, plots that you can see here.

Both of these panels depict resistance in animal populations. The top panel panel A, was faecal samples, and the bottom panel B was meat samples. And this, zero line would be the initial level of antimicrobial resistance in that population, and the plots, and show the risk difference after the intervention with the 95% confidence intervals being these whiskers.

And down here, you can see the overall result. So, overall, after an intervention of some variety with regards to antimicrobial use, the antimicrobial resistance risk is decreased and seen true down here. So, it suggests we can't pull any, real, knowledge from this with regards to Individual farms or farming systems, because there were so many different types of study in this systematic review, some on individual farms and some across, whole countries even.

But the general trend is you make a change, towards more responsible or reduced antibiotic use, and you'll see reduced resistance. So, oops, sorry. So, this is another study, this is a, nationwide level study, by Callans at A.

And this one looks at, Belgian livestock species. So, you can see that, the blocks, show. Antibiotic use, and the lines show antibiotic resistance.

And over the course of 2011 to 2015, and there's reduction in the use of penicillins, trimethoprine, fluoroquinlines, and the total use of antimicrobials, with associated reductions in resistance. But for the florenacor group, interestingly, the antibiotic use actually increased alongside a decreasing trend of resistance. This does suggest that maybe for different groups of antibiotics, maybe, antibiotic use influences antibiotic resistance differently, or that there are potentially other factors involved here.

So, this is all good on, a national level, and we know that in the UK we are reducing our total antimicrobial use, as we saw from the VARs report statistics. But the question really is, on individual farms, what can we do? So, for example, is there any points for a farmer to struggle away with selective dry cow therapy if actually feeding waste milk to his calves?

Is going to make the biggest difference antimicrobial resistance relatively on that farm. And that's a question that needs, and to be looked into a lot more going forward. But here at the University of Bristol, some of the researchers have done a study on dairy farms in the UK looking at these questions.

And the OSA, study is what it's called, and that stands for one health selection and transmission of antimicrobial resistance. And I will return to that, study and the findings of that study towards the end of this presentation. But first, I just want to make sure that we're all on the same page with understanding what types of resistance, is generally being investigated in these research papers.

I, just want to cover what ESPL means, and make sure you know the different types of resistance that are in the studies that I'm gonna be sharing with you. So, ESPL stands for extended Spectrum beta lactammase. And there are various bacteria that can produce ESPLs, not just E.

Coli, for example, Klebsciella can also produce it. ESBL bacteria produce an enzyme which can hydrolyze penicillin and cephalosporins, which means they're resistant to these antibiotics. And this form of resistance is encoded by mobile genes called plasmids, and these can be transferred between bacteria, both of the same type and different types.

The ESPL bacteria are classified according to the type of the. The enzyme they produce. So, the E.

Coli that produce extended spectrum betylactammasecetax cefotaximase are classified as CTXN. The CTX standing for cefotaximase. And these bacteria are resistant to most 3rd and 4th generation cephalosporins, which, as you know, are important in human medicine.

So, the CTX, the M bit is, due to the fact that, the bacteria is simultaneously discovered in Munich and in France. And Munich was given the M. And, in France, it was named after the researcher who discovered it and was given the name M1.

So, when they found that these two strains were identified, identical, sorry, it was given the name, CTXM1. It's, been found to cause, Identified cause infections in humans in the early 1990s. Again, plasmid-mediated transferable resistance.

It's become the most common form of SBL, in humans and in animals globally. And it was first reported in the UK on a dairy herd, in 2004, and that was then reported, by TaletL in 2005. And as you can see from the graphic, there are 5 different groups of genotypes, And different strains are more prominent in different parts of the world.

So, AMC and beta lactamases are, enzymes produced, by, bacteria that work in a similar way to CTXM, ESPLs but are rarer. It's also plasma-mediated form of resistance, but you can get chromosomal an expression, which means it can be passed between bacteria of the same type or different types. CMY2 is the, betylactommase of widest global distribution.

And And a C betylactommase is preferentially hydrolyzed, narrow, broad and expanded spectrum cephalosporins, and therefore resist inhibition by clavulanate. But they don't convey resistance to fourth generation cephalosporins. Again, they, they can be detected not only in E.

Coli, but also in clepsella and in salmonella. So Here we are thinking about what are the risk factors for antimicrobial resistance on individual farms. And, of course, one of the obvious, most obvious answers is to think about antimicrobial use on the farms.

And certainly, that has been demonstrated by a number of studies that we'll look at in the this presentation. And antimicrobial, use in a population does influence the presence and the prevalence of antimicrobial resistance in that population, but that's not the only influencing factor. And there are lots more besides.

So I'm just gonna put up here some that are kind of postulated or some that have been, investigated, as well as antibiotic use, as, in total. So that would include different antibiotic classes. Using antibiotics prophylactically or metaphylactically, using topical versus parental treatments and how that might influence antibiotic resistance on the farms.

Farm husbandry, how that might influence resistance, calf rearing practises, dry cow management and hygiene, both in particular areas of a farm and, in general. So other factors that have been investigated are things that are coming in from the farm, so buying in animals and quarantine protocols, the sharing of farm staff and farm equipment, the management of slurry on a farm. And then other, researchers have looked at, aspects beyond the farm gate, as it were.

So things like wildlife coming in and out of the farm, and how that might, convey resistance onto and off of a farm. Waterways coming through between farms, and similarly footpaths even with people coming, between, different farms. So, the first paper I just want to share with you is this one by Trangressor at our, published 2006.

This looked at a number of farms, 18 farms in Ohio, and, as you can see, 1,266 dairy farms sampled individually, and the faeces, tested against 16 antimicrobials. They were testing for this AM CB tylactamase gene. They found, that reduced susceptibility E.

Coli was more likely to be isolated from herds in which cefti fuel was being used. 25 times more likely, in fact. At the individual cow level, though, there wasn't any association between recent cety fuel use and isolation of reduced susceptibility E.

Coli. And there was no relationship between the percentage of cows on a farm, which had reduced susceptibility to E. Coli, and the percentage of cows being treated with ceftiure in that herd.

So, the conclusions of this study being that there wasn't a correlation, within individual cows, between treatment and resistance status. It suggested that there was, is rapid transmission of antibiotic resistance between animals within the environment. And that if we're gonna make interventions, they really should be done at a herd level because that seems to be the level at which these kind of antibiotic risk factors are working.

So, another study here, looking at plasmids carrying betylactam A CTXM1. This is a comparison study of two dairy farms in the Czech Republic. So farm A was what we'd call a conventional dairy farm.

It had high parental and intra-mammary antibiotic use. It was regularly using 4th generation cephalosporin treatments for dry cow therapy and parental treatments in cows. And then we're comparing here with Farm B, which is an organic, slightly smaller organic herd with no cephalosporin use, doesn't use 3rd or 4th generation cephalosporins, and generally low and biotic use.

And the finding of this study was that there was a higher prevalence of CTXM1 producing E. Coli, on farm A, compared to farm B, and you can see the numbers here. So the conclusions here.

Being that, again, using 3rd and 4th generation cephalosporins was increasing the likelihood of ESBL E. Coli being present on a farm, and that there was herd-wide trends relating to the use of the cephalosporins or not using these antimicrobials at all. So, another study that I want to share with you is this one.

And two studies that we've looked at so far, specifically investigated the association between the use of 3rd and 4th generation cephalosporins on farms and the presence or absence of certain types of resistance, namely, ESPL resistance. But this, study was performed in the UK and was really the first study to try and investigate other factors which might be contributing to the presence of ESPL, E. Coli, on farms.

This study was set up because the first case of CTXM E. Coli was on a dairy farm in the UK and reported by Thiella Owl, in that paper in 2005, as I've already mentioned. And as you can see here, Teal was one of the, researchers on this paper.

And this paper is written by a group of staff and researchers all working at the Veterinary Laboratories Agency, as it was known at the time, which is a network of disease surveillance centres across the UK. And since the discovery of CTX MESBL E. Coli, at that time was classified as a new and emerging disease, it really wasn't known how widespread the bacteria were on farms in the UK or how they could be spread between animals on farms.

And it was assumed that similar to other And diseases we have like TB and BVD, that animal movements might play a significant role in the spread of that kind of resistance. And so they set up this study to look at the risk of CTXM E. Coli on farms that had a link with this original case farm through animal movements.

And then they also had a control group, as you can see here, in a similar geographic area to the farms that had movement, animal movement links to the, original farm. So, the results of that, study, is that there was no significant linkage, of detection of CTXM from the original study farm. So the movements between the original study farm and others seemed to not be significant.

In the risk for ESBL E. Coli on these farms. But what were risks were, open herd policy, having open herd policy and no quarantine of animals as they come onto the farm.

The storage of slurry in a pit, the storage of slurry in a lagoon also had a higher risk, but wasn't significant. The farms that had used 3rd or 4th generation cephalosporins in the previous 12 months or 4 times more likely to have ESPL E. Coli present.

And, the infrequent, so less than monthly, cleaning of calf feeding equipment resulted in an increased likelihood of having ESPL, E. Coli present, present on a farm. So we're starting to be able to potentially draw some general conclusions about these things from these studies, one being that high priority, critically important antimicrobial use, seems to repeatedly be coming out as a risk factor for ESBL E.

Coli on dairy farms. Similarly, biosecurity, particularly having open herd policies without any quarantine. And in this case, cleanliness specifically of calf feeding equipment seemed to be a risk factor for ESPL, E.

Coli and the farms. So, other work, in this area had found that, the prevalence of CTX and E. Coli was particularly high, in calves, in calf areas on the farms.

And in this study, which I'll only touch on briefly, this study was done on a different CTX known case farm, which used 3rd and 4th generation cephalosporins for a number of purposes, including dry cow therapy and, treating infections parentally in cows. So the results of this study was that 95.6% of sample calves on this farm was testing positive for CTXM E.

Coli at two days of age. . So also, cows and heifers were approximately 8 times more likely to test positive in the 10 days after calving than the 9 days before.

Different areas on the farm, had different prevalence of the ESBL E. Colis. Calves and calving areas tended to be higher in the antimicrobial resistance prevalence.

And interestingly, the prevalence in calves was decreasing from 90% at 53 days to only 10% at 117 days. And the researchers said that this correlates with the time at weaning, when most calves stop receiving waste milk feeds. So this was, increasing the, consideration that maybe waste milk was contributing to the fact that young stock were kicking out so much antimicrobial resistance on farms.

So some of the, that same research group went on to continue work in this area, and this is another UK study again on that original CTXM positive farm. This, study was set up to look at, where ESPL could be found, on a dairy farm, and how, those bacteria persisted in those niches on the farm. The farm investigated was known to use 4th generation cephalosporins in dry cow therapy and feed waste milk to calves.

As you can see, it's a commercial dairy unit, and the 250 cows on it. And the results they found was that the majority of the calves examined were shedding CTXM producing E. Coli in the faeces at high or very high levels.

None of them were shedding at low levels. The duration of shedding, ranged from 14 to 64 days, so a reasonable range there. And again, increased then, interestingly, that the cessation of shedding of CTXME cola was consistent with the time of weaning.

So the conclusions that they drew from this particular study was that calves, again, were contributing to the presence of CTXM ecoland dairy farms. That reduced shedding may coincide with weaning, interestingly. And that then was raising, increasing the suspicion of the fact that waste milk feeding was driving this ESPL prevalence and presence in calves on farms.

And this just as an aside, there's another paper published in 2014, done in the UK that found that 21.4% of waste milk samples on UK farms contained amounts of cefquina in them. So, again, maybe not an unsurprising link then, to, calves kicking out those levels of E.

Coli resistant, resistant E. Coli. So, again, just coming back to the conclusions we can draw from these and other similar studies at the time.

Again, HPCIA uses a risk factor, biosecurity, cleanliness. But now, we're starting to think more about the fact that just rearing pre-weaned calves and any calf and calving areas on the farm are likely to be high, it's a prevalence of ESBL. E.

Coli on these dairy farms. So, at this point, both from those largely UK based studies I've just highlighted, and more besides, it's well recognised that CTXM ESBL, E. Coli are found quite commonly in the faeces of cattle on dairy farms.

And, as per the previous study, calves seem to excrete high numbers of ESPL, E. Coli, if it's present on a farm. And at this stage, it was assumed that the use of certain antibiotics, so certainly 3rd and 4th generation cephalosporins will be selecting for the presence of this form of ESPL resistance.

But it was recognised that other factors were probably influencing this too. And some recent stuff. Studies had suggested that, antimicrobial residues residues in waste milk could be selecting for the presence of resistance on farms, both from residues in the waste milk getting into the environment, and also via the calf intestine and being then passed through into the calf faeces.

So, people then set out to investigate the effects of feeding, feeding waste milk to calves with antibiotic residues in it, to see if this would have any significant effect on the likelihood of calves excreting bacteria of these specific forms of resistance. So, this is one study, which is a longitudinal study. It was looked at a UK dairy farm known to use cefquinone.

And the aim of which was to assess the impact of feeding waste milk containing antibiotic residues. So waste milk plus antibiotic residues on the prevalence of these bacteria in the faeces of cars. It should be said that the waste milk plus antibiotic residues is just, the researchers weren't adding any antibiotics to this, waste milk.

It was just as, it was coming out of the milk, milk out of the cows. It just, waste milk that wasn't contributing to the bottle tank at the time. So the results of this study was that cefcrium a 4th generation cephalosporin, was detected in 87% of the waste milk samples on this farm.

So, a huge majority of the waste milk being fed to calves was containing a 4th generation cephalosporin. All environmental and sampling locations had CTXME, E. Coli in them, so it spread all over the farm, not just in the calf areas.

Significantly more penfloor samples were positive in the treatment group. So there was a control group which was fed milk replacer, which had lower levels of CTXM positivity. And calves in the treatment group shed greater numbers of CTXM positive E.

Coli than calves in the control group throughout the study, and shedding decreased at a slow rate in the treatment group. So, again, definitely contributing to the theory that calves are kicking out a lot of, ESB and E. Coli into their environments.

And that study, as well as others listed here in this green box, all contributed and were reviewed in a comprehensive review published in 2016 by the European Food Safety Authority. And you can see that here. And all of these papers supported the theory that feeding waste milk to calves, which had antibiotic residues in it, was contributing to, calves shedding high levels of ESBL E.

Coli into their environments on a farm. And that was in turn contributing to the presence and prevalence of the SPL E. Coli on dairy farms.

And so, following this review, RUMA, which is the responsible, use of medicines in Agriculture Alliance, issued a new position on the feeding of waste milk. And that was that waste milk, excluding colostrum from cows under the statutory withdrawal period for antibiotics should not be fed to young stock. So that was kind of that line in the sand there on, on, on calf waste milk feeding really .

As we know it. So, this is another influential study looking at the role, of calves in the prevalence of antibiotic resistance on farms. This is by Pereira etal.

And unlike the previous study, it discussed, look, this particular study looks at, calfs specific treatments. So, as you can see, 473 calves on 8 farms in the US, . State of New York.

3 E. Coli isolets are sampled per calf, and these are tested then against 12 antimicrobials, each for susceptibility. And these researchers were looking specifically at calf and antimicrobial treatments and how that affected resistance in these isolates.

And the results show that only refloxacin was significantly associated with the reduced antimicrobial susceptibility of E. Coli isolates, and that the treatment with ceftiphir, which is Third generation cephalosporin was associated with reduced susceptibility to ceftriaxone. And interestingly, also, as the results of this study, were that the use of other antimicrobials of different classes did not have a significant effect on, the islets, susceptibility.

So, again, coming out of the HPCIAs are, having more effect on the susceptibility of, E. Coli in these calves. So, here we can add waste milk feeding to calves into our list of risk factors which have evidence, a body of evidence behind them as a risk factor for the SPL antibiotic resistance on farms.

But then the question is, what other factors and might also affect resistance on farms, and there's likely to be lots of other factors, . Including buying in animals and sharing equipment and hygiene, as I mentioned before. And quite of the few of the studies I've looked at so far have really been just focused on the husbandry and management of calves and calving areas, because that, at the time was known to be, you know, an interesting potential risk factor.

But there are lots of other studies, that look at the farm as a whole, and a huge number of possible risk factors for antimicrobial at a farm level. So, I'm just gonna take you through a couple of them now. So, this is, a study that was done, in the Netherlands on quite a number of farms.

So 100, dairy farms across the Netherlands. They selected one, slurry sample per herd. They asked the farmers to do a questionnaire about management practises, and they also collected some data about antibiotic purchases to that farm.

The analysis showed that, the ESBL or AMC producing E. Coli are isolated from 41% of the slurry samples, so quite a number. The total animal defined daily dose of antimicrobials, at a farm level was not significantly different between ESPL or AMC positive and negative herds.

So, total antibiotic use didn't seem to be affecting the resistance levels on the farm. But again, the use of 3rd and 4th generation cephalosporins was associated with ESBL or AMC status of the farms. Other management factors that fell out as being, risk factors on these farms was treatment of all cases of clinical mastitis with antimicrobials.

A higher proportion of calves treated with antimicrobials, not applying teat sealants in all cows that dry off, and the use of a floor scraper, which seems to be a bit of an anomaly in the results, but maybe, the, authors suggested it could be something to do with just being bigger herds. But the rest of them, as you can see, do have mastitis treatments and calve treatments and in also dry cow management there. So this is a very similar study by a similar group, and this study looked at, organic herds, again, in the Netherlands.

So, similar, protocols to the, to the study. So, single slurry samples collected from the farm, a questionnaire on management practise, and, antibiotic purchase records. So, interestingly, and these organic farms, only 13% of the slurry samples were AMC or ESPL positive, so much lower than the 41% that was found in the conventional Dutch dairy farms.

Again, no difference in the total antimicrobial use affecting ESBL or AMC positivity or negativity of the herds. But interestingly, and conversely, to the previous study, no association between antimicrobial resistance and the use of the 3rd and 4th generation cephalosporin. So this raises the question whether there are different, interactions here on these lower use or organic use farms with the use of 3rd and 4th generation cephalosporins.

And risk factors that came out in this analysis, for ESPL or AMC E. Coli pre presence, were, pig farms within a 2 kilometre radius. So, maybe that suggests that, antibiotic resistance could be spread in dust, which has been found to be feasible between farms.

Parental treatment for clinical mastitis. And, again, some, you know, mastitis treatments came up in the other, other study as well. And, conversely, to the vast body of evidence that we, I discussed before, that feeding milk replacer to half a cast after lustrum was a risk factor for the higher odds of ESPL or an E.

Coli. Again, is that something to do with a difference in, interaction there on organic and low using farms, or is it something to do with the milk fat, the milk replacer was being fed the heifer calves on larger farms. It's unknown.

But what interestingly was found was that ESPL and AMSI, was being found on farms with low antimicrobial use. And so, therefore, it's likely that other factors, are associated with ESPL and AMSI herd status. So, just a summary, again, of where we're at so far with this.

So, things that have a body of evidence behind them. So, HPCIA use, maybe with different, associations or on organic or low use farms, but generally, a strong body of evidence to show that at herd level, this is definitely gives is a risk factor for antibiotic resistance on a farm. Biosecurity, so buying in animals without quarantining them and sharing equipment between farms has come up a couple of times on different studies, and in one there that proximity to pig farms.

So that's a question to be asked is, you know, is this This be true of other agricultural premises in the vicinity of a farm. Cleanliness has come up a couple of times on in one paper with general farm hygiene and another with farm calf feeding equipment as being risk factors for antibiotic resistance on farms. And having calf area.

So having any pre-weaned calves on a farm, definitely those areas, the calves are kicking out, antimicrobial resistance at higher levels. And having group calving areas as well has been a risk factor in studies. And again, like with, like, I've said, a, increasing and a big body of evidence, to suggest that waste milk feeding to calves is a risk factor for antimicrobial resistance.

Mastitis treatment. So, in one study, using parental treatment only to treat mastitis, and also using antibiotics in all cases of mastitis, is, is a risk factor, are risk factors in different studies for antibiotic resistance, and not using sealants in all cows was found in another study. But these here, I'm hoping you can see I'm pulling out some sort of general themes, of risk factors that, have evidence behind them.

So, just to summarise in a different form, you can see here, so we have got evidence for different antibiotic classes being risk factors. If you think about waste milk feeding, with residues, and prophylactic or metaphylactic, treatment of those calves is contributing to a resistance on farms. Parenteral versus over topical treatment seems to cause, and be a risk factor for antibiotic resistance on farms.

The way calves are reared, again, particularly with regards to waste milk feeding, Dry cow management, both with regards to the types of antibiotics that are being used in dry cow, therapies. So if they're HPCIAs or not, and the use of sealants can contribute to the risk factors. Buying in cattle without any, without any quarantine periods is a risk factor.

Sharing of farm farm equipment is a risk factor, and storing slurry in a pit or a lagoon even has also been found to be a risk factor. So we haven't covered these, sort of more external factors yet, and that's something I just want to show to you in the next couple of So, this is just one example of a study here that's been looked at, you know, other species that could be bringing resistance onto the farms and how, how that might affect the resistance that we're seeing on farms. And this, study was done on Ohio dairy farms and looking at European starling night roosts.

So they visited, 150 farms twice. And collected faecal pet samples from the farms. And they, most significant finding, finding of their study was that farms closer to starling night roosts were significantly more likely to have a high prevalence of E.

Coli, showing reduced susceptibility to cefotaxim and ciprofloxacin. So, again, We're not sure the, entire significance of this in the UK, for example, and, in species beyond starlings, but we know now that potentially, wildlife and vermin could be playing a role in transmitting antibiotic resistance between the farms that we're working on. So, there it is, the wildlife.

Also, there's evidence behind that being a transmission route for antimicrobial resistance. So I said I'd, get to it and share you, share with you the results of the OSA study from the group at the University of Bristol here. And, so that, study was done on 53 dairy farms in the UK.

Environmental samples from cows, young stock, and calf environments, as well as out in pasture land, were collected. These guys were doing monthly visits over basically a couple of years to these farms to collect these samples. And they were looking for Echili with betectomase genes, and they identified them by PCR.

And they analysed different risk factors, on the farm. So, they looked at farm management, they looked at antibiotic use of the farms. They looked at different sample characteristics, and they used some meteorological data, so, namely, the local temperatures at the time of, sampling.

And so the most significant findings from this, more recent study, is that 5.4% of the E. Coli were carrying the betylactammase CTXM.

And so reasonably small, numbers of individual samples being found there, but 79% of the farms are positive for betylactamma, CTX, and E. Coli. And it's thought that potentially, because in this Study, they were repeatedly sampling the same farms over a couple of years, every month, but comparatively to other studies that, for example, those studies in, on the Dutch dairy farms when they were just, sampling them once, and 11 sample, and maybe sort of, there's a cumulative effect, of finding resistance on these farms.

So, a high level of, on sort of farms across the study, as it were. And, interestingly enough, they, like I said, were collecting meteorological data, and they found that a low temperature resulted in low CTXM E. Coli positivity on the farms.

And that average monthly temperature had a significant effect on the betylact A CTXM E. Coli positivity. And that suggests that there's a temperature dependent fitness burden of resistance to these types of bacteria.

And it's just, again, for the academics among us, definitely need to potentially think about the fact that temperature and sort of ambient temperature when we are collecting, samples, definitely maybe needs to be, you know, being factored into studies going forwards. And, you know, for the rest of us thinking about when we're reading papers, thinking about where the paper. Was done, what type of time of year?

And could temperature be influencing the results and the kind of, detectability of resistance on farms. And again, for policymakers and, and that going forwards, maybe temperature needs to be, factored in as well. If, if going forwards, we might start to look for antimicrobial resistance levels on our farms.

So, the main, otherwise, the main findings of this study were that high levels of antibiotic resistance and beta lactam A, CTXM, E. Coli, was found in farm locations that were dominated by young animals. So again, adding to that body of evidence that suggests that young animals and calves have much higher levels of, ESBL E.

Colis that they're, shedding, and there was low levels of fat being found out on the pasture land. Again, contributing to the HPCIA risk factor. In this study, cefquinine, which is a 4th generation cephalosporin dry cow therapy, was most significantly associated with, the detection of CTXM E.

Coli in calf samples. So, dry cow therapy affecting this, shedding of ESBL E. Coli from calves.

And that, again, contributes to evidence that's, already in the body of evidence, and that I've already discussed. But a new finding that hasn't been reported in other studies that came out of the OStar project was that there's a clear positive association between the use of ramacetin as part of dry cow therapy combination and the odds of finding CTXM, E. Coli, and calf samples.

So, it's unknown why or how ramacetin might be affecting this. Maybe it's kind of a, Co-resistance, situation on a plasmid or something like that, and that needs some further work, but that was also found to be associated on these farms. So, a final summary page for you now, really.

So, just to show where the OSA study backs up, some of the evidence. So, again, HPCIA use being a risk factor, having pre-weaned calves, kicking out a lot of, antimicrobial resistance is gonna be, is a risk factor with more evidence behind it now. And again, dry cow management, certainly, the use of HPCIAs in dry cow management is, a risk factor for ESBL E.

Coli. On our farms. And this, OStar study just, adds the addition that, additional information that potentially temperature could affect how much, antimicrobial resistance is detected in certain studies, because it seems to affect the detectability, as it were, of some of the antimicrobial resistance we're looking for.

But this isn't the only study to, have shown this. And this just, is one final study to share with you. It was published in 2018, and investigated the role of climate and additional factors on the distribution of antibiotic resistance across the United States.

And the finding, this study was that an increase in temperature of 10 degrees across the region was associated with associated with an increase in antibiotic resistance of 4.2, 2.2, and 2.7.

7% for the common pathogens, E. Coli clepsella and Staphylococcus. So, again, there is evidence that, temperature can affect the levels of antibiotic resistance that we are seeing on, on farms and detecting, in samples.

So, like I said, something to consider if, antimicrobial resistance is something we're looking to monitor going forwards. So, like I said, the final, summary slide here for you. And as I've already said, this, you can see there aren't any kind of, strong rules about, what is gonna be the main difference in antimicrobial resistance on particular farms.

But hopefully, you can start to get a feel for the trends that we're seeing across a lot of different, evidence. And, as I've already said, all I've shown you today is really a handful of, different. Papers, but there, and they're a lot more besides, but again, they're adding to these themes.

So, high priority critically important antimicrobial use, you know what they are. These interventions to reduce the use of HPCIA seem to need to be done on a herd level. So you're either using them or you're not.

And if you're not, then you're reducing the risk of antimicrobial resistance on those farms. And like I said before, this might have a different, influence on organic and on low using in farms. Biosecurity, so buying in animals without a quarantine, sharing equipment and potentially proximity to pig or maybe other agricultural farms, agricultural industry could have an effect, cleanliness.

With respect to general farm hygiene and specifically calf feeding equipment, we know has evidence behind it, as a risk factor. Calf areas. So just having pre-weaned calves, in calf calf areas and particularly group calving areas as well, are all, contribute to the risk of antimicrobial resistance on farms.

And, and potentially, you know, when we're thinking about this, we know, if we know this information that the pre-weaned calves are gonna be kicking out a lot more, antimicrobial resistance. Maybe just some simple strategies of biosecurity to ring fence those areas of a farm, get farm and workers to be washing their hands more prudently after they've been in with the calves and that sort of thing, to try and break those, links, of the, those, you know, those antibiotic resistant bacteria, spreading throughout the farm. Calf feeding, like I've said, has a good strong body of evidence behind the fact that waste milk feeding of calves increases the risk of antibiotic resistance on a farm.

Various, aspects of mastitis treatment might affect resistance on a farm, but particularly in certain studies, using parental treatment to treat mastitis and giving antibiotics to all cases. So again, this as, farm vets might come up in, we might think about. When we're making protocols for farm to try and move away from using parental treatments where possible.

And is it possible even to treat more mild cases without antibiotics, at least to start to try and reduce the amount of, cases that we're, we're using antibiotics in? Dry cow management. Again, no hard and fast rule, but the strongest one seems to be the high priority, critically important antimicrobial use in dry cow therapy.

So, again, as vets, can we try and, start making protocols or, you know, encourage farmers to move away from the use of HPCIAs in dry. Cow therapy, knowing that that does, is has strong evidence that that affects antibiotic resistance back in calves and calf areas. And also, one study, not using sealants in all cows, was a risk factor as well.

So, trying to encourage farmers to do that on their farms at dry off. And like I said, we can't really have any control over the temperature on our farms, but just knowing. That that can affect, the, the papers that we read in the studies that we, we are looking at, when, when we're looking at this, data.

So, that's the end of this, presentation. I hope that, like I said, unfortunately, won't have been able to offer you the, golden bullet answer to how to reduce antimicrobial resistance on your farms. But hopefully, you can see looking down this list that A lot of these areas are things that we're working towards anyway, and hopefully, improving things like biosecurity, cleanliness on various, farms, with farmers that you're working with, is gonna have benefits beyond, the prevalence of antimicrobial resistance on the farm.

It's hopefully gonna have Disease and welfare implications as well. And so knowing that you can work around these areas and also have an effect on antimicrobial resistance on the farms we're working at in and on, hopefully gives you some, some confidence there, and gives you some more confidence to go and have those discussions with farmers. So, thank you for listening to my presentation, and please feel free to send in any questions that you have.