Ticks Continue Spread of AGS Meat Allergy

Widely distributed in the Northeast, South, and Midwest US, excepting the far north areas, the lone star tick (Amblyomma americanum) has been gaining notoriety with its ability to spread Alpha-gal syndrome (AGS), a delayed allergy to beef and pork, through its bite. While several tick species can spread the allergy, the lone star tick is the primary vector in the US.

AGS is named for the sugar molecule, Galctose-alpha-1,3-galactose (or Alpha-Gal for short) which all mammals, except primates (including humans), carry. It is passed to humans when a tick feeds on a mammal (e.g., a deer), ingests the Alpha-Gal, then bites a human, transmitting the molecule to the person. In some people, this causes the immune system to produce antibodies to fight the perceived threat posed by the  sugar which then triggers the release of histamines causing an allergic reaction to all mammalian meats and products. Although the most commonly reported symptom is hives, one study found that more than 50% of cases also reported anaphylaxis.

The allergy is difficult to diagnose because the reaction can be delayed up to 10 hours, with symptoms ranging from hives, sneezing, stomach pain/nausea, vomiting, diarrhea, and shortness of breath to life-threatening anaphylaxis. As with any food allergy, once a person is afflicted with AGS, they must be vigilant about their food choices, sometimes completely avoiding mammalian meats (i.e., (such as beef, pork, lamb, venison, goat, and bison) and their products (e.g., milk, cheese, gelatin, glycerin, etc.).

The first state in which a reportable condition was made was Arkansas in September 2023; since then, with lone star ticks most prevalent in the southern states, allergy rates have surged to 32% than elsewhere. However, even that is gradually changing, as the ticks continue to move north and west, as winters become less severe and air temperatures increasingly warm, enabling tick survival.

With climate change allowing for longer warm seasons and increasing habitats for ticks, as well as for host animals, such as deer, mice, and raccoons, we are likely to see a continuing increase in AGS cases in new regions both in the US and globally due to the expansions of suitable tick habitats.

For more information on Alpha-Gal Syndrome (AGS) and recommended protection against ticks, see TAG’s Tick-born Infectious Disease Fact Sheet from our Infectious Disease Fact Sheet Library.

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