There is a food allergy, known as alpha-gal syndromewhich can develop after a tick bite Lone star (Amblyomma americanum): “injects” a sugar called sugar into our body galactose-α-1,3-galactosewhich our immune system does not recognize and attacks as a real one allergentriggering an allergic reaction, even quite severe, in case of red meat intake such as that of pork, beef or lamb, and, in some cases, milk or its derivatives, while fish and poultry they can be eaten, forcing the unfortunate ones to have an (almost) vegetarian diet. The tick most frequently associated with the phenomenon is widespread in the United Stateswhere more than 110,000 suspected cases were identified between 2010 and 2022, but cases are often underreported. Fans of the Florentine steak will immediately be alarmed, but can be partly reassured by the fact that the syndrome is, to this day, still quite rare. The first case was reported in the United States in 2007, but it was very difficult to trace the causes understand the cause-effect relationship between tick bite and allergy to red meat given that the symptoms appear in a delayed form, even 6-8 hours after ingestion of food and not at the time of the puncture. Even today this allergic form is not easily recognized and its incidence in the population is still underestimated: sometimes patients are mistakenly diagnosed with urticaria.
What is the syndrome Alpha-gal caused by the tick bite and where it is widespread
The cells of mammals, with the exception of primates and therefore humans, contain a sugar called galactose-alpha-1,3-galactosea disaccharide known as alpha-gal. If a Lone star tick bites, for example, a dog, a cattle or a sheep for its blood meal, it also takes in the alpha-gal sugar and, if the next victim is a man, it also transfers the disaccharide together with the saliva of the mint which, moreover, contains alpha-gal itself.
Considering that it is absent in us humans, when it enters our blood, our immune system immediately identifies the molecule as foreign and triggers an immune response with the production of specific antibodies, the immunoglobulin E (IgE). From that moment, the person becomes allergic to alpha-gal sugar and the disease remains latent until what is ingested red meatmilk or its derivatives containing alpha-gal.
Those affected can no longer eat red meat or its derivatives; beef, pork, lamb, rabbit, horse, goat and sheep, as well as their entrails, cause allergies following the tick bite and the production of IgE immunoglobulins. Other foods at risk are bouillon cubes, ready-made sauces, condiments and meat extractsbut also milk, dairy products, butter and yogurt. Even the edible jellies or those used to coat some drugs, if produced from animal collagen, can cause problems. AND Poultry and fish can be eaten since this disaccharide is not present in birds and fish products.
What is Amblyomma americanum, the lone star tick
As already mentioned, several species in the world are carriers of alpha-gal in salivary secretions, but the best known is the Lone star (Amblyomma americanum) also because it was the first to be identified as a cause of food allergy. They are often found in woodlands as parasites of coyotes, deer and cattle. Adults are active from April to the end of August. The female is distinguished by the presence of a white spot in the center of the brownish-brown bodyhence the nickname Lone star i.e lonely star. Each female is capable of laying 2,500-3,000 eggs.
In the United States, the syndrome is most prevalent in south-east and along the Atlantic coastwhere the Lone star tick is most common. More than 110,000 suspected cases have been identified in the period between 2010 and 2022, but cases are often underreported.
In Australia, the allergy is concentrated along the east coast where ticks are present Ixodes holocycluscarriers of alpha-gal. In Europethe allergy is widespread where the Ixodes ricinus, the common woodland tick. To date, the greatest incidence is reported in Sweden and in Germanybut reports range from Portugal to Poland and Turkey. Cases also occur in Japan and South Korea and South Africa. Few cases have been disclosed in Central and South America, but there have been reports in Panama, Brazil and French Guiana.
How to recognize the bite and what to do against the allergy
Patients accuse urticariaskin rashes, and gastrointestinal symptoms, such as nausea, vomit and diarrhea, which typically occur 6 -8 hours after significant exposure, but can also occur respiratory difficultiesdizziness and feeling of fainting. In areas where certain tick species are endemic this syndrome should be taken into account when recurrent cases of urticaria occur.
Among the main precautions reported by allergy societies, given that there is currently no vaccine, it is recommended to avoid consumption of red meat which is already effective in 80% of cases, check the labels of packaged foods to make sure there are no meat-based ingredients. Use caution when eating in restaurants.
To avoid the root problem, it is best to avoid being bitten by ticks by taking appropriate precautions when outdoors, wearing long trousers and socks, boots that cover the ankles; avoid walking in tall grass and carefully check your clothing once you return home.
