26 June 2012

Some tick bites can lead to red meat allergy

This unexpected and intuitively unexpected correlation has been reported in the May 2011 issue of J. Allerg. Clin. Immunol.  Here are some excerpts from the abstract:
In 2009, we reported a novel form of delayed anaphylaxis to red meat, which is related to serum IgE antibodies to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal). Most of these patients had tolerated meat for many years previously. The implication is that some exposure in adult life had stimulated the production of these IgE antibodies.... Prospective studies on IgE antibodies in three subjects following tick bites showed an increase in IgE to alpha-gal of twenty-fold or greater...

The results presented here provide evidence that tick bites are a cause, or possibly the only cause, of IgE specific for alpha-gal in this area of the United States. Both the number of subjects becoming sensitized and the titer of IgE antibodies to alpha-gal are striking. Here we report the first example of a response to an ectoparasite giving rise to an important form of food allergy. 
And from the discussion:
This evidence includes following the response prospectively in three cases, a strong correlation with histories of tick bites, epidemiological evidence that these antibodies are not found in regions where tick bites are rare, and the correlation with IgE antibodies...

Our original observation was that the distribution of anaphylactic reactions to cetuximab was similar to the maximum prevalence of Rocky Mountain spotted fever. The major vectors of RMSF in this region are the ticks D. variabilis and A. americanum, and the geographic range of A. americanum has been expanding over the last 30 years, probably in parallel with the massive increase in the deer population...

Although many different patterns of tick bites have been reported, three forms stand out:
1. A few bites from adult ticks that persist for weeks or months, remaining pruritic. The most severe case of this kind reported having two tick bites removed surgically 6 months after the original contact.

2. Repeated bites often around the ankles in subjects who work outside or hunt regularly. In a few cases, the local reactions to the ticks have been so severe as to preclude further work outside.

 3. Multiple bites from larval ticks, generally 10 or more, but often hundreds, which are again severely pruritic, but generally do not last more than a few weeks...
Fascinating.  I would never have expected this.  For those interested, here is the distribution map of documented cases:

Via the discussion thread at Reddit, where some readers report their personal experiences with meat anaphylaxis and discuss methods of tick removal.


  1. Interesting map. This obviously means that several (13?) US states are simply unaware of the problem because their disease reporting requirements are either highly questionable or non-existent. Strange, no

    1. This isn't necessarily true, on reflection, of the states to the west of the red "bone", and it isn't a good map to start with, because instead of showing red dots which indicate concentrations of recorded cases and instances of one or two isolated cases, it gives the impression that each red state has many such cases. But the actual number of cases is not listed here and in the reddit article, it is hard to find. However, on P5 of the NIH article, there is talk of 125 cases in central Virginia and greater than 300 overall. If I lived either side of the middle of the "bone", I'd be worried! Why aren't authorities detecting the cases that are sure to be there. Ticks don't understand borders.


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