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Tick allergy

Mammalian meat allergy is on the rise in Australia and the surprising cause - a tick bite. Dr Jonica Newby meets Dr Sheryl van Nunen, the clinician who discovered the link. She found that if the tick had fed off another mammal first, the tick's blood was infected with a sugar called alpha gal. Once bitten by the infected tick some of our immune systems react to alpha gal causing an allergic reaction. This story is a must see if you want the latest tips on how best to remove a tick.

Duration: 15min 6sec

Broadcast:
Tue 17 Feb 2015, 1:00am

Published:
Tue 17 Feb 2015, 1:00am

Transcript

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UPDATE: When killing a tick, Dr Andy Ratchford now recommends you apply up to five squirts of the freezing agent to make sure the tick is killed.

NARRATION

A coastal getaway, a BBQ, it's the Australian ideal. But imagine if one day you reached for a steak and ended up in emergency...

Joy Cowdery

My blood pressure had dropped, my tongue was swollen.

NARRATION

..with life-threatening anaphylaxis.

Joy Cowdery

You must be joking. I mean, who's allergic to red meat?

Dr Jonica Newby

It's called mammalian meat allergy, or MMA. Unheard of until a few years ago, it's on the rise up and down the eastern seaboard, with two cases now being diagnosed a week just in this area. But what's more astonishing is what causes it. We've now discovered it's triggered months, even years, earlier by a seemingly unrelated event - a bite from a tick.

NARRATION

It's an incredible story of scientific detective work with implications for anyone who visits the coast...

Assoc Professor Sheryl van Nunen

We have the highest prevalence in the world.

NARRATION

..or ever has to remove a tick.

Dr Andrew Ratchford

They are surprised when we tell them that probably the reason is because they've been removing the ticks incorrectly.

Dr Jonica Newby

The truth is, if you've ever been bitten by a tick you may already have a mild version of MMA and not even realise it.

NARRATION

When Joy and her husband Nick Cowdery bought this idyllic getaway 25 years ago, meat was just part of living the good life...

Joy Cowdery

Veal marsala, osso buco...

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..as were ticks.

Nicholas Cowdery

There are a lot of ticks here.

Joy Cowdery

I would've been bitten every time we came here.

NARRATION

In hindsight, there were early signs of mammalian meat allergy, but they were the kind of thing any of us would probably just ignore.

Joy Cowdery

When I looked back, I found that I'd had a number of gastro-intestinal problems but I'd never, ever put it down to something like meat.

NARRATION

Then one day Joy was making a beef casserole for a friend.

Joy Cowdery

So I tasted it to see whether the meat was cooked. After just over an hour, I said to Nick, 'I really don't feel well.' And with that, I started to itch all over. Bright red. My tongue was swollen.

Nicholas Cowdery

Very scary and, obviously, it was something that required immediate medical attention.

NARRATION

A week after her brush with death, she was referred to a specialist to undergo an allergen test and went home to her husband with the shock diagnosis.

Joy Cowdery

'Guess what? I'm allergic to red meat.' And he said, 'You can't be!' And I said, 'Well, that's what the blood test showed.'

Nicholas Cowdery

I needed to be convinced finally.

Joy Cowdery

So we had an experiment. OK, let's try roast lamb tonight.

Nicholas Cowdery

It wasn't the best decision.

Joy Cowdery

At about one o'clock in the morning I woke up and I was itchy all over. And I just very slowly started to go red.

Nicholas Cowdery

No more tests after that.

NARRATION

It's not surprising people have trouble believing in Joy's tick-induced meat allergy because its discovery is so recent many doctors still haven't even heard of it. And the person who made this astonishing link works here. She's immunologist, cum allergy super sleuth, Professor Sheryl van Nunen.

Assoc Professor Sheryl van Nunen

Hi. How are you?

NARRATION

Sheryl was working on Sydney's North Shore when she started to notice an unusual cluster of cases, of which Joy's was case number 23.

Assoc Professor Sheryl van Nunen

I started seeing people who had a more unusual form of anaphylaxis, in that they'd wake up in the middle of the night. Normally with anaphylaxis you have the allergen - be that peanut, prawn or penicillin - and then within half an hour you're usually having quite a serious reaction. And so it's quite easy to go back to the probable provoking factor.

NARRATION

But in these midnight cases, none of the usual suspects - like bedbugs - fit. So she decided to try looking at their last meals.

Assoc Professor Sheryl van Nunen

Joy, did you bring any ingredients of the food of that meal?

Joy Cowdery

Yes, I did.

Assoc Professor Sheryl van Nunen

Good.

NARRATION

Dr van Nunen is unusual in that she does live meal tests, instead of allergens from a bottle. Basically, she pricks the food and uses that for the skin test. They may be why red meat allergies in adults had never been picked up before. And to her amazement, her patients were allergic to pork, beef, lamb - even venison.

Assoc Professor Sheryl van Nunen

And kangaroo and buffalo and obviously we then realised that this was all mammalian meat.

NARRATION

But why? What would cause a person who loved meat suddenly to have such a violent reaction? And then she spotted it - all her patients had a history of tick bite. Could it be caused by ticks?

Assoc Professor Sheryl van Nunen

I literally wouldn't believe it myself, but every time there was a middle-of-the-night anaphylaxis it would turn out to be mammalian meat after tick bite. You add up to 20 people or so and you think, 'Good heavens, I've got to really do something about this. We've got to somehow bring this to the attention of my colleagues because the tick, when you look at the distribution, is all down the east coast of Australia and you could see the majority of our population is exposed by virtue of where they live or the way they choose to do their recreation or even work.

NARRATION

But how does a tick cause an allergy months later to a food like red meat? To find out, let's go catch some.

Dr Jonica Newby

What every tick hunter needs - some repellent and a state-of-the-art tick catcher.

No, in fact that's a great misconception, it's a real myth. Very rarely ticks climb more than about 60cm, because it just gets too dry for them. But once they're on you, they can actually walk over the body and they can spend two to three hours before they find a site to attach. It's a nice little park this. I think it's lovely.

NARRATION

And it looks like our tick trawling has delivered.

Stephen Doggett

So this is the adult stage of the paralysis tick, the one that's so problematic for our pets and the one that can actually lead to the mammalian meat allergy.

NARRATION

And here's how.

Dr Jonica Newby

Just look at these enormous mouth parts. Ticks feed on blood so when they attach they insert these under your skin and inject you with a local anaesthetic, which is why you don't feel it at first. The trouble is, at that point they're also injecting you with part of the blood of whatever animal they fed on before.

NARRATION

And that blood, if it came from any mammal other than humans, contains a small sugar called alpha-gal. Other mammals have it. We don't.

Assoc Professor Sheryl van Nunen

Alpha-gal is two galactose, or two sugar molecules, stuck together and it forms part of every mammal except humans, great apes and Old World monkeys.

NARRATION

What's extra strange about alpha-gal is that it's a carbohydrate. Normally things that cause serious allergies are all proteins. But being processed by the tick makes this harmless sugar seem like something else.

Assoc Professor Sheryl van Nunen

What I wondered was whether the tick bite could actually switch the human to being pro-allergy and that's what we think is probably happening.

Dr Jonica Newby

So the tick bites a mammal and picks up alpha-gal. Now, once inside the tick, the alpha-gal binds to a tick protein to form a complex. When the tick then bites me, it's this complex that's injected straight into my bloodstream. Now, normally my immune system would just ignore the alpha-gal and attack the tick protein, but this time they're coming in together and my immune system suddenly goes, 'Oh, that's tough, that alpha-gal, that's dangerous too.'

NARRATION

Our immune system has now been trained to react to alpha-gal and it's found in all red meats. An immune system attack on the wrong target is what we call an allergy. A massive attack that threatens our whole system, that's what we call anaphylaxis. So how common is it?

Assoc Professor Sheryl van Nunen

Oh, we have the highest prevalence in the world. Other places where they consider it to be quite prevalent are ten times less. And that probably is due to the fact that our tick is very efficient at promoting the problem.

NARRATION

A thousand cases of MMA have now been diagnosed up and down the east coast - basically, wherever ticks are common. Which means moist, coastal bush areas stretching up to 100km inland. Hotspots are around Sydney and also Noosa. But now doctors are becoming more aware of it we are starting to see cases in Victoria. More importantly, there are no doubt thousands of people with low-grade MMA who don't know it yet. That's because, as was Joy's case early on, it just manifests as occasional nausea or diarrhoea, easily mistaken for a gastro bug.

Assoc Professor Sheryl van Nunen

Well, if you do have intermittent gastroenteritis, you know, if you think you had a funny meal every so often, then it might be worth your while taking meat out of the diet and see if those symptoms disappear. Then you should put it back in and see if those symptoms reappear. And then do that a sufficient number of times until you're convinced that that was the cause.

NARRATION

But it's not just meat allergy you have to worry about. A growing number of people are becoming allergic to the tick bite itself. And it's so severe they end up here.

Dr Jonica Newby

Believe it or not, acute life-threatening anaphylaxis to a tick bite is now 25 times as common around here as a severe reaction to a bee sting and it's a medical emergency.

Dr Andrew Ratchford

So it can happen within seconds or minutes of a tick being removed.

Assoc Professor Sheryl van Nunen

75% of people with tick anaphylaxis have a grade 3 or grade 4 reaction. Grade 3 is, 'We can do great things for you with adrenaline and oxygen.' Grade 4 is, 'We hope your will's up to date and we'll have a crack at it.' So these are very serious anaphylaxis that are occurring.

NARRATION

Unlike meat allergy, where alpha-gal is involved, this tick allergy is a reaction to a protein from the tick saliva itself. Which is why it comes on so quickly and severely.

Dr Andrew Ratchford

Just pop your arm out for me.

NARRATION

And interestingly, the people who have the meat allergy are a different group to the tick-allergic.

Dr Andrew Ratchford

People have had bites for 20 years and then all of a sudden this year they'll come in with an anaphylactic reaction.

Dr Jonica Newby

Bit surprising to them, I imagine. Are people shocked when you explain what it is?

Dr Andrew Ratchford

They are and also shocked when we tell them that probably the reason is because they've been removing ticks incorrectly.

Dr Jonica Newby

So are you saying that tick anaphylaxis could be prevented altogether if we just remove ticks the right way?

Dr Andrew Ratchford

Yeah, if you squeeze the tick, that causes the allergen to enter the bloodstream, which causes the anaphylactic reaction. If you remove the tick correctly without squeezing it then you don't have those problems.

NARRATION

Unfortunately most of us instinctively do the wrong thing. So you have a tick. How should you remove it?

Dr Jonica Newby

Here's my tick. Now this is what most of us will do - we'll either scratch it off or reach for the household tweezers. Now this is precisely the worst thing you can do. As you remove the tick, you squeeze it and all its contents go straight into your bloodstream.

Assoc Professor Sheryl van Nunen

What they need to know is household tweezers are tick squeezers.

Dr Jonica Newby

So what should you do? Well, you should go to the chemist and buy a spray containing ether. So something like Wart Off, or Medi Freeze Skin Tag Remover. Place the nozzle conveniently over the tick and spray. Feels cold - freeze the tick, and wait about ten minutes for the tick to die. Once it's dead, you can just brush it off.

Assoc Professor Sheryl van Nunen

'Freeze it, don't squeeze it', would be our advice.

NARRATION

So that will kill the adults. But what about the tiny ticks? The little larvae or nymphs? Now these are my little larval ticks and for these I'm gonna use a cream containing permethrin. Now this is basically the same kind of cream as you get for scabies. Just rub that in. The ticks will all die and soon you'll be able to just rub them off.

Dr Andrew Ratchford

We dab them. Don't grab them.

NARRATION

Meanwhile, back at the lab...

Dr Jonica Newby

Bloody hell! I've got a tick! This is not deliberate and it's really itching. OK, let's get the Wart Off out, please. It's sizzling. I guess I wait for it to die now.

Dr Stephen Doggett

Solid frozen.

NARRATION

And to my surprise the itch went away completely in an hour. This new method really works. As for Joy, she's not taking any chances these days.

Joy Cowdery

This is my tick protection gear. Um, I spray my body with Rid to begin with, then I spray my clothes with Permoxin. And then I'm ready to garden.

NARRATION

And while Joy may no longer be able to eat red meat, she can at least still drink red wine.

Nicholas Cowdery

Not all is lost.

Dr Jonica Newby

No. So cheers to this beautiful place.

Nicholas Cowdery

Cheers. Thank you.

NARRATION

And for the latest advice on tick bite first aid, visit the Catalyst website.