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EP 29: Prof Brendan Wren – Why Campylobacter Never Went Away and The Amoeba Link
109 Plays1 month ago
Campylobacter on supermarket chicken may have slipped from the headlines since the Food Standards Agency (FSA) surveys of 2014–15, but it hasn’t gone away.
In this Poultry Network Podcast episode, hosts Tom Willings and Tom Woolman revisit one of the poultry sector’s biggest food‑safety challenges and ask why Campylobacter remains a leading cause of gastroenteritis — with an estimated ~500,000 cases a year in the UK and a cost to the economy of over £1 billion.
Joining them is Professor Brendan Wren (London School of Hygiene & Tropical Medicine), Co‑Director of the Vaccine Centre and Co‑Director of the GlycoCell Engineering Biology Mission Hub.
Brendan explains why Campylobacter is so well adapted to birds (optimum growth around 42°C), how tiny doses (around 100 cells) can cause severe illness in humans, and why the “Campylobacter conundrum” persists: the bacterium is oxygen‑sensitive and doesn’t generally spread person‑to‑person, yet seems ever‑present in the food chain.
The conversation explores a provocative “missing link” — free‑living amoebae. Brendan’s research suggests amoebae can act like a Trojan horse, sheltering Campylobacter inside durable cysts and potentially making it more invasive when it emerges. If that’s true, it could reshape on‑farm thinking about prevention, surveillance and water hygiene.
Key topics include:
• What changed after the FSA findings — boot barriers, thinning practices and supply‑chain controls
• Why Campylobacter peaks in summer (and why it’s not just barbecue season)
• PCR‑based detection of Campylobacter within amoebae, and what it means for understanding transmission
• Practical interventions: drinking‑water filtration, UV, improved hygiene and targeted anti‑amoebae approaches
• Next steps: systematic farm sampling (including free‑range) to test the hypothesis and refine control strategies
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Transcript
Intro
Introduction to Campylobacter Discussion
00:00:15
Tom Willings
And welcome to another edition of the Poultry Network podcast. My name is Tom Willings.
00:00:21
Tom Woolman
And I am Tom Woolman.
00:00:23
Tom Willings
Today's episode is focused all on the topic of campylobacter.
Campylobacter's Historical Context
00:00:27
Tom Willings
Now, you might not have heard of campylobacter a little while because 10 years or so ago, it was in the news, a regular feature on the back of an FSA study of 2014 and 15 that found a high level of prevalence in in chicken on supermarket shelves.
00:00:44
Tom Woolman
Yeah, there was ah there was a time really where it was ubiquitous, wasn't it?
00:00:45
Tom Willings
a
00:00:48
Tom Woolman
You couldn't get away from it at all the conferences. That's what that's what people were talking about. and And it was all certainly retailers were were really interested in in terms of how you were managing your camp pilot back to schools.
00:00:59
Tom Willings
And then the supply chain, I had a quick stint in retail around that that time and um yeah supply chains turned themselves inside out at farm level and in the process, in the call chain, particularly um in packaging to yeah um you know to make amends or or or to to to mitigate as as much as possible. But it remains a food safety
Expert Insights on Economic Impact
00:01:21
Tom Willings
issue. And and we're joined today by um a guest who knows an awful lot about the subject. So just allow me to introduce to you all and Professor Brendan Wren.
00:01:32
Tom Willings
Brendan's the co-director of the Vaccine Centre and co-director of the Glycocell Engineering Biology Mission Hub at London School of Hygiene and Tropical Medicine. Brendan, that's one enormous job title, but it speaks to the to to the um the power of your knowledge sir so welcome to the podcast and um yeah why why is campylobacter back to back in the news
00:01:57
Brendan
Good afternoon, Tom. ah Well, campylobacter never went away. It's a leading cause of gastroenteritis worldwide and leading cause of gastroenteritis in the UK.
00:02:08
Brendan
It's estimated that there are half a million cases in the UK alone at a cost of UK economy of over billion pounds. And that's the equivalent in the US, where it's about seven billion pounds, billion dollars a year, and the EU. So it's never gone away. It's still a really persistent problem worldwide.
00:02:27
Tom Woolman
That's an astounding number. So the Campylobacter could cost the UK a billion pounds a year in terms of...
00:02:35
Brendan
Indeed, yeah. And there have been many independent estimates that it is at least ah a billion pounds a year to the yeah UK economy. So that includes lost time at work and you know hospital costs and and everything else. So it's still a a major, major issue.
Adaptation of Campylobacter in Birds
00:02:52
Tom Willings
did ah Did I read in in sort of research for today's episode that sell something like 70% of gastroenteritis or cases associated with food poisoning relate back to chicken and compilobacter?
00:02:52
Tom Woolman
So...
00:03:06
Brendan
ah They relate back to compiler bacteria. It's not always poultry that is the problem for cappo compiler bacteria. It can enter the food chain via other routes, but certainly we know that ah that that's the main route ah and the consumption and handling of poultry is a big issue.
00:03:26
Tom Woolman
what's What's so special about poultry? Because because I was reading that Camp Ilobacter is present in all sorts of um guts of all sorts of animals.
00:03:33
Brendan
Yeah. It is present in many different animals, but it's elegantly adapted to the crop of avians, so not just poultry, other birds.
00:03:44
Brendan
And part of clue is the optimum growth temperature of Compilobacter is 42 degrees, which is the body temperature of birds. Obviously, humans is 37 degrees.
00:03:56
Brendan
So it's clear that once a few cells of Compilobacter get into birds, we know it multiplies really rapidly and there can be trillions of different compiler bacteria present within a crop of a bird so it really expands massively and yet you know just 100 cells causes severe bloody diarrhea in humans and potentially other complications.
Farm Management Practices Against Campylobacter
00:04:23
Tom Woolman
So going back to the introduction when we were talking about when the industry was focusing quite heavily on Campylobacter in the past, and there were a number of measures which were brought in to contain the spread of Campylobacter, some of which Tom has referenced. And I remember some of the specific measures that came in on farm. There were things like ah boot barriers. That's really when boot barriers became mandatory.
00:04:49
Tom Woolman
single boot barriers we now seem to have double boot barriers in a lot lot of places as well and also at that stage the industry was mostly doing two thins in a broiler crop and um after a thin you you do get a spike in terms of campylobacter and so certainly in retail the the industry has moved to a one thin program um where where birds are only gone in for to take some out at one point in the in the course of the crop. So and I think probably up until this point, a lot of these measures have reduced the levels from from where they were and the situation is is managed and it is monitored, even though it isn't in the news.
00:05:30
Tom Woolman
It still is monitored by buy all these businesses and and by retail. ah But the reason we wanted to talk to you, Brendan, is that you've been doing some research which is helping to us to understand even more about how Campylobacter lives and how it spreads and and and and might offer some clues in terms of how we might be able to deal with it more effectively in the future.
Paradox of Campylobacter's Spread
00:05:54
Brendan
Yes, compile it back to the problem of poultry houses and farms, you know and statistics show that. um I've been studying it for 30 years, mainly you know how and why it causes such acute disease.
00:06:09
Brendan
And it really is an enigmatic pathogen with many peculiarities. um One of the main peculiarities is it's It's the leading cause of gastrointestinal disease in the world.
00:06:24
Brendan
It seems to be omnipresent, but it's actually oxygen sensitive, so it doesn't grow in the atmosphere. So we call this the compile about the conundrum or paradox. you know How can it be seem to be present everywhere but it doesn't grow in the air we need special conditions to actually persuade it to grow um and it doesn't generally spread from person to person so uh so there's this real paradox as to you know how compiler bacteria is such a leading cause of disease still and yet it ah apparently doesn't like surviving in the environment or atmosphere
00:07:01
Tom Woolman
Because you're right, because if I think about, if I was going to talk to people about gastroenteritis and that sort of thing, people start talking about norovirus and, you know, ah certain viral things.
00:07:11
Tom Woolman
But these are things that spread from person to person. so so if So if one person's got it and everyone else is acutely aware that they might get it as well, whereas with campylobacter, it's, yeah, it's's it's not like that, even though actually the the level of prevalence is probably much higher.
00:07:13
Brendan
Yeah. Indeed.
00:07:25
Tom Woolman
Hmm.
Role of Amoebae in Campylobacter Invasiveness
00:07:26
Brendan
date
00:07:27
Tom Willings
And your research, Brendan, points to the humble amoeba. Is that right?
00:07:31
Brendan
It does. So ah the humble amoeba is, so I guess, about 20 times the size of Compilobacter. Amoebae are everywhere. They're omnipresent in water environments and soil environments.
00:07:44
Brendan
And, you know, the the ancient, simple unicellular organism. And basically their diet is to eat bacteria. So they they have pseudopods that encapture bacteria, eat them.
00:07:59
Brendan
And of course, bacteria aren't happy with this. So they will, over long evolutionary period of time, try to counteract this. uh and our studies uh have shown that compiler bacta has a very intimate relationship with meb it counteracts all the all the toxic threats that maybe have in kind of an evolutionary arms race and it's we you know, under the microscope of looking at amoebae and stained compiler bacteria, we can see the compiler bacteria fighting back. So this is a long evolutionary process that these these two organisms have had.
00:08:35
Brendan
And we think that this could be the missing link in terms of understanding why compiler bacteria so prevalent.
00:08:41
Tom Willings
I may have misunderstood the the brief, of course, but um did I understand correctly that the compiler bacteria is actually living inside the amoeba?
00:08:52
Brendan
It does, and it's quite happy to be there. And then when the amoebae forms cysts, which are these very durable cells, almost like spores, compiler bacteria is still in there.
00:09:05
Brendan
And what I asked, lab studies have shown that when compiler bacteria comes out the other side, it's actually more invasive, it's more aggressive. So ah living within the amoebae makes compiler bacteria that's more aggressive. so once it reaches the ah poultry population, chickens, it can really take off.
00:09:26
Tom Willings
so So it's like a Trojan horse. The amoeba is the Trojan horse for the Compilobacter. It's living in ah in a protected environment, ah improving its sort of durability, and then out it pops with, you know, but how many multiple times more pathogenetic, ah genetic is it?
00:09:44
Brendan
Yeah.
00:09:44
Tom Willings
can't even say the word, but invasive. um
00:09:47
Tom Woolman
theres there's ah There's a few tongue twisters in this podcast, aren't there, Tom?
00:09:49
Tom Willings
you got Aren't there just, yeah, for a humble egg guy, yeah.
00:09:53
Brendan
You've got it exactly right. So acts like a Trojan horse, the amoebae, carries the compiler back to in. Amoebae seem to be everywhere as well. And once compiler back to comes out the other side, you know we're shown in a lab, it's that much more invasive, aggressive, and and that's where we believe the the problems lie.
00:10:15
Tom Willings
So how how do we better then detect it for one and get a true read on how much is there and then combat it?
00:10:24
Brendan
so people suggested amoeba in the past it's a potential way uh of that you know can be in poultry houses um but in the past people try to culture compiler factor from amoeba and as i mentioned compiler back is difficult to grow and and they failed by that but we use a more pcr sensitive approach and we can detect a compiler factor within about 30 percent of wild amoeba these aren't even ones associated with farms so we think that this has been missed we have a more sensitive way of actually detecting the compiler better in amoeba and then the percentage numbers were a lot higher than we expected so i guess we're proposing as a fairly simple solution would be to ah obviously remove amoeba from
00:11:15
Brendan
and the opportunity within a poultry house.
Strategies to Control Amoebae in Poultry Houses
00:11:19
Brendan
So this could be through drinking water because they may be quite happy living in drinking water, you know, better filtration, UV, it's simple and done ah simple hygiene measures would help not just to reduce compilobacter, but if what we're saying is true, then actually we should be looking at removing amoebae and that would remove the compilobacter.
00:11:43
Tom Woolman
Does this also somehow help to add to our understanding of why we see a ah peak in summer months in particular for the Campylobacter?
00:11:54
Brendan
Yes, that's one of the other mysteries about Kompilobacter. The incidence in the summer months goes up tenfold. You can almost...
00:12:01
Tom Woolman
just I thought it was barbecue season that was the that was the problem initially, but the the the problem is there is more Campylobacter around as well, isn't it?
00:12:10
Brendan
Yeah, there's just such a huge number and you could almost set your watch by it, but it's not barbecues because in wet summers when there's been no barbecues, you still get the increase. So for what you know I used to think is barbecues was the explanation, but clearly we think there's something else.
00:12:29
Brendan
And I guess what's key about Amoebae is that they bloom in the summer months, that their numbers naturally go up. So that could be partial explanation for why compile it back to its high in the summer months.
00:12:43
Brendan
But that's circumstantial evidence. you know We're looking forward to try and really prove all of this.
00:12:49
Tom Woolman
yeah
00:12:49
Tom Willings
I want to just leap back to the um the more sensitive detection that you just mentioned there. And there's a little alarm bell ringing in my mind to think that you know there will be um yeah farm assurance protocols in place at the minute and then the same in factories and and and testing of finished product as well, all using assurance.
00:13:09
Tom Willings
certain sets of technology but are you pointing to a future where perhaps we need to um you know ah acknowledge the type of testing that's being conducted because they're going to give very very different results and with more sensitive testing you know what what do you think the um the practical measures not just on farm but right the way through the chain ought to be to um to to deal with higher rates of um detection
00:13:34
Brendan
I think I may have misled you there. I think these methods of detecting comp compiler back to within the food chain and and from farms that it's pretty good. ah i was referring to detecting compiler back to within a maybe. So in the past, people tried to culture it and generally failed.
00:13:54
Brendan
But, you know, we're saying with. PCR sensitive methods we can actually detect compiler back to an amoeba so I think you know at the moment through the food chain they really only look at the you know the poultry or after thinning for compiler back to but we're in earlier stage ah you know there's this missing part of the life cycle compiler back to if if you look for it there as sensitive methods, we believe you can find it. And that might be ah better improved intervention method.
00:14:28
Brendan
You know, whether you know we're we're starting to also think about screen, there are many different antimicrobial, anti-amoebae agents, such as chlorhexidine, quaternally ammonium compounds, and many others. so So I guess what we're proposing that, you know, simple measures measures early on that can eliminate as much remeviation as possible will also simultaneously remove compiler back to
00:14:54
Tom Woolman
Yeah, so it could well be that at the moment when people are doing water tests on farm, um i mean, fairly typically you might do one early on in in the crop when you're brooding and and the temperature in the house is warm and the water's warm as well and the flow rate is low and and you're testing it for the for the TVC, the total ah viable count, and um and also for stuff like Pseudomonas.
Enhancing Testing and Hygiene Practices
00:15:16
Tom Woolman
So it could be that actually we start looking for amoebae in that as well. I don't know how easy that is to do in in in the sort of labs that we've got at the moment or whether it might in might have to have a bit more imagination in terms of how we actually test for these things.
00:15:31
Brendan
Yeah, actually amoeba are quite difficult to culture as such. so ah But maybe we're also looking at PCR sensitive method to detect amoeba. That would be a lot simpler.
00:15:44
Brendan
But certainly i think the issue is trying to culture compiler back from amoeba is difficult. you You can culture Pseudomonas, E. coli, Salmonella. you know there These are bacteria that are naturally growing in atmosphere.
00:15:58
Brendan
Compile it back to dozens. So that's why it's a tough knot to crack.
00:16:03
Tom Willings
and So we've got we've got a takeaway message for farmers, which which is, well, everyone in the chain, all all all about hygiene and, um you know, that that this isn't as easy to eradicate as perhaps one's first thought. And we're going to dig a little deeper.
00:16:18
Tom Willings
um What about your research? what's the what's the What's the next step for your research? and And what's your sort of call to the industry?
00:16:27
Brendan
of Well, weve we've ah I'm a lab scientist basically, so i did visit a poultry farm recently, to Tom Warnham and his sister Caroline Scott, they very kindly showed us around and the sal tower so he did poultry houses, which was an eye opener for me and my colleagues. And they've allowed us to take samples, which we're investigating at the moment. So so what we plan to do is to do this on a systematic basis, a number of farms, particularly farms that have ah had a history Compilobacter and even free range farms as well.
00:17:05
Brendan
um And to really prove our theory and then to start to implement some measures that we could use, whether it's targeted anti-amoeba agents, disinfectants, or whether it's more simple hygiene measures that could be done.
00:17:23
Brendan
um you know, once we really... was just so impressed to see poultry has this sealed unit, and to me it's a problem of seeing what goes in and what comes out. and So we've obviously tried to detect it's at the litter, ventilation,
00:17:40
Brendan
the food, or the feed, and and but we we suspect that actually the drinking water may be of importance.
Conclusion and Call to Action
00:17:50
Tom Woolman
And that's interesting because there's been a huge amount of focus in the last 10 years on drinking water. If I think back to when I started in poultry, a lot of people weren't doing anything for hygiene with their drinking water. Some people were throwing a few chlorine tablets in and hoping for the best. Whereas most farms now would have a system where they are select dosing a chemical or different chemicals, chlorine dioxide or hydrogen peroxide ah set rates and people are testing more.
00:18:20
Tom Woolman
And so I think this could be quite an interesting evolution um along the um along the way for for water hygiene in poultry. Yeah.
00:18:30
Brendan
I agree, yeah.
00:18:31
Tom Woolman
Yeah, yeah, yeah. Brilliant.
00:18:34
Tom Willings
Well, that sounds like a good way to end the episode. So Professor Brendan Wren from the London School of Hygiene and Tropical Medicine, thank you so much indeed for imparting your knowledge, for joining us um today um to you. i hope you've enjoyed listening and and taken something away from today's interview. and A reminder that if you're not already subscribed, please do so and make sure that our podcasts podcast episodes drop into your your inbox every Friday. Until next time. Thank you.
00:19:03
Brendan
Thank you.