There’s a new tick spread disease that’s been making the news for a couple of years:
Based on the Wiki article, it isn’t a new pathogen like a virus or bacteria that is being spread to humans, rather its a carbohydrate that is picked up by the tick and then injected into the human.
I would think this mechanism of transfer has been going on for thousands of years, and therefore the allergy has also been going on for thousands of years, undiagnosed or studies. Is that a true liklihood? So instead of a new disease all of the sudden, we’ve always been getting it, but its been relatively rare and not recognized.
You’re probably right. It’s not a pathogen like MRSA that has recently evolved. It’s a benign carbohydrate, common in food meats, that’s triggering a dysfunctional immune response.
However, the immune system is subtle, so it’s hard to know for sure. I can describe some conjectured scenarios in which it might be a recent phenomenon.
The adaptive immune system learns all “self” antigens (molecules that our body makes that it should not respond to) early in development. It then detects any other antigen as “foreign”, but will only usually respond if additional criteria are met. Foreign antigens are expected in the digestive tract, so they will not trigger a response unless the immune system already “knows” them as pathogenic markers.
In many cases, the presence of the carbohydrate under the skin from tick bites seems to trigger alpha-gal sensitivity. But the immune system is sophisticated - just injecting something under the skin isn’t usually sufficient. What might be happening is that the tick bites also contain some pathogen that triggers a valid immune response; but the immune system also learns to respond to the harmless alpha-gal that’s injected by the tick in conjuction with the pathogen, assuming that it’s part of the pathogen. Subsequently, large quantities of alpha-gal in the digestive tract from meat trigger a dysfunctional response.
So, a lot of things might have changed in the tick population recently. Most plausibly, perhaps, some non-fatal pathogen that has recently swept through and infected most of the tick population, and is now getting injected in bites along with the alpha-gal that has always been there, now tricking the immune system into thinking that alpha-gal is part of a pathogen.
It’s also possible that some other totally unrelated manufactured substance that humans have been exposed to only recently has an epitope that coincidentally resembles alpha-gal, and that this is increasing sensitivity. I don’t know how plausible that is for a carbohydrate.
Thanks, that make much sense, and I think is part of what I originally heard a couple of years ago for a possible mechanism. So its possible that just ingesting and then injecting Alpha-gal has been going on forever and hasn’t produced a response, but coupled with a new infectious agent does
It may also be the case that the immune systems of modern humans living in generally more hygienic conditions are more likely to ‘overreact’ to such an exposure - see the Hygiene Hypothesis.
So, historically, given widespread chronic exposure to intestinal worms, more varied skin and gut flora, etc. etc., perhaps an exposure to alpha-gal and whatever the adjuvant factor in tick saliva is would not have resulted in alpha-gal allergy. Just like kids who grow up eating dirt out in the barnyard don’t tend to get peanut allergies.