Mammalian Meat Allergies – from East to West

Tick bites can cause mild to life-threatening allergic reactions, including anaphylaxis, to mammalian meats such as beef, pork, lamb, kangaroo, goat, and venison.

Symptoms may be mild to severe (and can also be life threatening), including angioedema (swelling), urticaria (hives) and anaphylaxis, and occurs a few hours after eating meat such a beef or pork which contains the oligosaccharide alpha-gal.

The reaction may not be instantaneous and there may be no symptoms of allergy for several months after the tick bite.

The allergen in the meat to which people react is called ‘alpha-gal’, a carbohydrate, and some people are so sensitive they react to mammalian products, particularly milk and gelatine although any product derived from mammals may cause allergic reactions, making avoidance very difficult as the allergen may be found in a wide range of agents used in medical treatments and supplements as well as in foods and even wine.

Although the mechanism is currently unknown, it has been suggested ticks that previously fed on other mammals may introduce alpha-gal to humans when people are bitten by a tick. As alpha-gal is not recognised, the human body mounts an immune response, which includes the production of human IgE antibody specific for alpha-gal.

The condition has so far been identified in Australia and in the United States, however, the numbers of those affected is substantial and appears to be increasing with additional cases identified in Spain and Sweden. 

In an article in the West Australian newspaper recently, it was reported a bushwalker developed the allergy.  There is nothing startling about this except that the man lives in Denmark, Western Australia, nearly 4,000 kilometres away from the NSW Northern Beaches.

The Northern Beaches in NSW have been known as a hotspot for MMA (mammalian meat allergy) for some time. The link between tick bites and MMA was first identified in 2007 by Prof Sheryl Van Nunen and her colleagues at the Royal North Shore Hospital in Sydney.  Prof Van Nunen diagnosed people with the complaint occasionally from the 1980’s, however, it has become increasingly prevalent since about 2003.  In her practice, she diagnosed over 500 patients (between 1985 and March 2014, with the great majority having presented from 2003 onwards) and diagnoses an average of two people per week with the complaint.

In Australia, the condition is thought to be caused by the Australian paralysis tick, Ixodes holocyclus, found in a narrow band along the east coast. Like its European and North American counterparts (I. ricinus, I. scapularis, I. pacificus) this tick has a host range that includes a variety of mammal species and, when the opportunity arises, people.

It was also reported recently that a six year old girl in Perth died from drinking milk. Emergency services were called to the girl’s home however paramedics were unable to save her.   Just two days later, another toddler was accidentally given milk at a childcare centre. This time, doctors were able to save the child after being given three shots of adrenaline before being rushed to emergency.

Without any clear research in Australia about the havoc ticks and vectors are causing to humans it cannot be discounted that MMA is not to blame for any number of allergic reactions.

Article by Anne Ryan.  Opinions in this article are mine and do not reflect the opinions of the LDAA.