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MAMMALIAN MEAT ALLERGY AND TICKS


You can develop a mammalian meat allergy (MMA) after a tick bite. This type of tick-induced allergy is becoming increasingly prevalent, particularly on Australia’s eastern seaboard.


Tick bites can cause a MMA, specifically an allergy to the carbohydrate alpha-gal found in mammalian meat. Common mammalian meats include: beef, lamb, goat, pork, kangaroo and rabbit. People with MMA can also react to mammal products, including their milks and gelatine.


MMA was first described in 2007 and has since been reported in 18 different countries worldwide. Depending on the country, different ticks species are involved in MMA. Within Australia, 95% of tick bites are caused by the Australian paralysis tick (I. holocyclus). The paralysis tick is found along most of the eastern seaboard of Australia and just a single bite from a nymph stage (immature) or adult can trigger MMA.


Australia has the highest prevalence of MMA, occurring at 113 per 100,000 population. Of significance, up to 60% of Australians live in regions where the I. holocyclus paralysis tick is endemic.


If a paralysis tick bites you, and/or if it is then squeezed/compressed, it can transmit its saliva that contains multiple salivary protein allergens as well as alpha-gal. Alpha-gal is a carbohydrate formed from the combination of two galactose molecules by the enzyme alpha-galactosyltransferase. Alpha-gal is a constituent of the connective tissues of many mammals, but is not found in the tissues of humans. As mentioned, it is known to be present in tick saliva. As alpha-gal is foreign to the human immune system, it can stimulate an immune reaction that later produces a mild to severe allergic reactions to red meats, such as beef, pork and lamb (plus other mammal products).


Signs and symptoms of a MMA reaction are often delayed and typically occur around 3-6 hours (up to 2-10hours) after eating mammalian meat or related products; for example, you eat a steak for dinner, then a reaction occurs in the middle of the night. Signs and symptoms can include:

  • Hives, itching or itchy skin

  • Swelling of the lips, face, tongue and throat (or other body parts)

  • Wheezing or shortness of breath

  • A runny nose

  • Abdominal pain, nausea, vomiting or diarrhoea

  • Sneezing

  • Headaches

  • Anaphylaxis


People with allergic reactions to mammalian meats are advised to avoid all mammalian meats (beef, lamb/mutton, pork, goat, horse, kangaroo, venison and other exotic mammals). Artificial blood (made from beef) and all forms of gelatin should also be avoided.


If you suspect MMA, see your GP or an Allergist as soon as possible.


References

Medicine Today | March 2021, Volume 22, number 3

https://allergyfacts.org.au/allergy-anaphylaxis/food-allergens/mammalian-meat-allergy

https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/tick-allergy

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