One tick red meat can do with­out

Is there a tick/bandi­coot con­nec­tion to a clus­ter of Syd­ney peo­ple with a se­ri­ous al­lergy to red meat? Bianca No­grady re­ports

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THEY were just or­di­nary pork spare ribs, prop­erly cooked and harm­less. But they were enough to land Peter Moore in hospi­tal with a se­vere al­ler­gic re­ac­tion. ‘‘ It wasn’t in­stan­ta­neous,’’ says Moore, 32. ‘‘ Maybe a cou­ple of hours later I went to bed and woke up with hives, re­ally big welts cov­er­ing my body.’’

When he be­gan hav­ing dif­fi­culty breath­ing, his wife rushed him to hospi­tal.

Sev­eral months later it hap­pened again, this time af­ter a meal of meat­balls, and then again a few months later af­ter beef na­chos. Moore had no known al­ler­gies and was in per­fect health, which left him and doc­tors puz­zled as to the cause. ‘‘ At the time, I wasn’t eat­ing beef or pork at home so we stitched it to­gether that it must be some­thing in the meat, like a preser­va­tive or some­thing,’’ says Moore.

But it wasn’t any flavour­ing or preser­va­tive — it was the meat it­self.

Moore had de­vel­oped a very rare al­lergy that when­ever he eats red meat causes full­blown ana­phy­laxis, an ex­treme im­mune sys­tem re­sponse that can cause breath­ing dif­fi­cul­ties, sud­den drop in blood pres­sure, un­con­scious­ness heart fail­ure and even death.

And he’s not the only one. Nearly 50 adults liv­ing in one small cor­ner of Syd­ney have be­come al­ler­gic to red meat, most of them in the past five years.

Sh­eryl van Nunen, head of the al­lergy de­part­ment at Syd­ney’s Royal North Shore Hospi­tal, first be­gan notic­ing this strange al­lergy clus­ter around five years ago. The first pa­tient with red meat al­lergy had ac­tu­ally ap­peared in her clinic nearly 20 years ago, but given the con­di­tion’s rar­ity, van Nunen as­sumed it was a once-in-a-life­time case. She couldn’t have been more wrong.

‘‘ Then there’s a gap of some years, and then in the last five years there has been a del­uge,’’ van Nunen says. Forty-nine adults have since come to her at­ten­tion, all with se­vere al­lergy to red meat and al­most all past or present res­i­dents of Syd­ney’s north­ern beaches, a dis­trict known as ‘‘ the penin­sula’.

All th­ese peo­ple re­act to beef, lamb, goat, and es­pe­cially to veni­son, buf­falo and kan­ga­roo. The rarer the meat, the stronger the re­ac­tion. While some get a milder re­ac­tion caus­ing vom­it­ing and di­ar­rhoea, most ex­pe­ri­ence ana­phy­laxis. They range in age from 21-63 years old. There are slightly more women than men. Most pa­tients are un­re­lated, al­though there are a hand­ful of fam­i­lies where sev­eral mem­bers — not nec­es­sar­ily blood rel­a­tives — have the baf­fling con­di­tion.

Yet there are no ob­vi­ous clues as to why such a large group of peo­ple from such a small area should de­velop such a rare al­lergy. ‘‘ They’re all sizes and shapes,’’ van Nunen says. ‘‘ The com­mon thing is the ge­o­graphic lo­ca­tion.’’

But af­ter the first few pa­tients a pat­tern started to emerge. ‘‘ Af­ter you’ve seen a cou­ple of peo­ple and the story’s the same, I like to my first ques­tion of you will be ‘ what hap­pens a cause of tick-re­lated al­lergy, a not un­com­know what’s hap­pen­ing to them so I al­ways when you’re bit­ten by a tick?’,’’ she says. mon con­di­tion, par­tic­u­larly in tick-in­fested take a fam­ily his­tory of al­lergy,’’. In one case, van Nunen saw a pa­tient from ar­eas. Per­haps there was cross-re­ac­tiv­ity be-

This process turned up an­other im­por­tant in­ner Syd­ney who was veg­e­tar­ian but had tried tween the tick al­ler­gen and some­thing in red com­mon­al­ity. Ev­ery sin­gle pa­tient, bar one, red meat — with ana­phy­lac­tic con­se­quences. meat? had ex­pe­ri­enced a larger than nor­mal re­ac­tion ‘‘ I said, ‘ you’ll think this is a very strange The pos­si­bil­ity gave van Nunen an­other to tick bite. That is, they’d de­vel­oped a 5-10 ques­tion, but have you ever had a large lo­cal thought: is there a con­nec­tion be­tween ticks cen­time­tre-sized welt at the bite site. re­ac­tion or any re­ac­tion to a tick?’,’’ van and bandi­coots? Bandi­coots are om­niv­o­rous

Ticks are a par­tic­u­lar prob­lem along Sy­dNunen re­calls. It turned out the pa­tient had mar­su­pi­als, which hap­pily eat meat, so it may ney’s north­ern beaches, es­pe­cially the par­a­ly­moved away from the north­ern beaches be that when the tick bites the bandi­coot, it sis tick so dreaded by pet own­ers. Ix­odes pre­cisely be­cause of a prob­lem with ticks. some­how ac­quires a meat-like al­ler­gen from holo­cy­clus thrives in the moist gul­lies and Sur­pris­ingly, an al­lergy to two things at once the bandi­coot. When that same tick then bites na­tive bush of the Penin­sula. Its num­bers are — so-called ‘‘ cross-re­ac­tiv­ity’’ — is fairly a hu­man, that al­ler­gen could pass to the new boosted fur­ther by large pop­u­la­tions of com­mon. Pa­tients al­ler­gic to, say, birch pollen host and sen­si­tise them to red meat. res­i­dent bandi­coots, which serve as un­will­ing may also re­act to ap­ples, stone fruit and The an­swer could come from the United hosts for the tick. legumes. That’s so be­cause there are sim­i­lar­iS­tates. Ray Mullins, an al­lergy spe­cial­ist in

The ap­par­ent link be­tween a strong re­ac­tion ties be­tween the re­ac­tion-pro­vok­ing sub­Can­berra, re­cently at­tended an al­lergy con­ferto a tick bite and red meat al­lergy seemed stances, or al­ler­gens, they con­tain. There are ence in Philadel­phia where two pre­sen­ta­tions strange. But the more pa­tients van Nunen saw, even doc­u­mented cases of cross-re­ac­tiv­ity were made that added more pieces to the the more she be­came con­vinced the con­nec­be­tween cow’s milk and beef al­ler­gies in puzzle. tion was real. chil­dren. Re­searchers in­ves­ti­gat­ing peo­ple with red

‘‘ It’s come to the stage now that if you come This raised the ques­tion in van Nunen’s meat al­lergy had dis­cov­ered a new anti­gen — from (the north­ern beaches), par­tic­u­larly the mind as to whether there might be crossa sub­stance that pro­vokes an im­mune re­sponse penin­sula, and you have an ana­phy­laxis and re­ac­tiv­ity be­tween ticks and red meat. Tick — in mam­malian pro­teins. They called the you don’t un­der­stand why that oc­curred, then sali­vary al­ler­gen had al­ready been iden­ti­fied as anti­gen al­pha-Gal. Mean­while, an­other team of re­searchers re­ported that they’d dis­cov­ered an un­usu­ally high rate of al­ler­gic re­ac­tions to a par­tic­u­lar can­cer drug in cer­tain parts of the coun­try. This can­cer drug also hap­pened to con­tain al­pha-Gal.

‘‘ There was a 10-fold higher chance that if you were be­ing treated in th­ese Amer­i­can states, you’d have an al­ler­gic re­ac­tion,’’ Mullins says. He sus­pects an en­vi­ron­men­tal trig­ger in those states is sen­si­tis­ing peo­ple to al­pha-Gal. Tan­ta­lis­ingly, ticks are en­demic in those re­gions.

‘‘ It may be that there’s al­pha-Gal in the tick and peo­ple get a tick bite and, for what­ever rea­son, the per­son de­vel­ops an al­ler­gic re­ac­tion to al­pha-Gal in tick saliva,’’ Mullins sug­gests. ‘‘ Then the same sub­stance present in some­thing else they con­sume sud­denly trig­gers a re­ac­tion.’’

Mullins says there was dis­cus­sion at the con­fer­ence about anec­do­tal ev­i­dence of a clus­ter of peo­ple who had de­vel­oped red meat al­lergy af­ter tick bite. How­ever he has some reser­va­tions about the tick the­ory: ‘‘ When a per­son eats 25kg a year of red meat or more, why should a bite from a tick make you al­ler­gic to red meat?’’.

To find out, Su­ran Fer­nando, a clin­i­cal im­mu­nol­o­gist at Royal North Shore Hospi­tal, is analysing blood from red meat al­ler­gic pa­tients to work out ex­actly what al­ler­gen trig­gers their al­lergy. ‘‘ The burn­ing ques­tion for me is, is this a true cross-re­ac­tiv­ity,’’ says Fer­nando.

The only way to an­swer this ques­tion is to do lab­o­ra­tory stud­ies to see if there is a com­mon pro­tein that peo­ple are re­act­ing to, and be­cause peo­ple re­act to more than one type of red meat, is this pro­tein com­mon to a variety of red meats, he says.

Some work has al­ready been done over­seas to tease out the al­ler­gen in red meat. ‘‘ Pre­vi­ous re­search (iden­ti­fied) some­thing called bovine serum al­ler­gen,’’ Fer­nando says. ‘‘ The ques­tion is whether there is a pro­tein in tick saliva that might be sim­i­lar in struc­ture to bovine serum al­ler­gen.’’ If so, this would sug­gest the tick saliva is in­deed the cul­prit, and is sen­si­tis­ing peo­ple to re­act to the bovine serum al­ler­gen in the red meat.

Mean­while, the Aus­tralian ‘‘ tick team’’ is keen to find more peo­ple such as Peter Moore, and mon­i­tor them to see if they de­velop red meat al­lergy. As well, van Nunen says she has a ‘‘ con­tract out on the bandi­coot’’ to get some sam­ples from a dead bandi­coot and see if a com­mon al­ler­genic fac­tor emerges

While many ques­tions about the nuts-and­bolts of red meat al­lergy re­main unan­swered, Peter Moore, for one, is re­lieved to have a di­ag­no­sis. ‘‘ For the pre­vi­ous five years I was just think­ing it was a preser­va­tive, that I would never re­ally know what the prob­lem was,’’ says Moore. ‘‘ Now I know ab­so­lutely what it is, I’m much more care­ful.’’

Pic­ture; bob Fin­layson

Re­ac­tion: Peter Moore re­calls a se­vere al­lergy to a tick bite not long be­fore a meat meal brought him out in welts

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