Alpha-gal Syndrome
The characteristics, symptoms, diagnosis and treatment of alpha-gal syndrome.
Background
Alpha-gal syndrome is a tick-associated disease which very rarely affects people following a tick bite. It is an allergic response, not an infection, and cannot be transmitted to other people.
Alpha-gal syndrome occurs when a person becomes sensitised to a sugar called galactose-alpha-1, 3-galactose (alpha-gal), a molecule present in the saliva of several species of ticks but absent in humans. Following a tick bite, some individuals produce IgE antibodies to the molecule, and these antibodies may also react with meat products including beef, lamb or pork. This causes an allergic response, which usually starts with gastrointestinal symptoms 2 to 8 hours after consuming the meat product. The allergic response may progress to shock, swelling and other symptoms of anaphylaxis, due to activation of IgE antibodies which trigger a reaction called Mast Cell Activation Syndrome (MCAS).
The majority of cases of alpha-gal syndrome are caused by the Lone Star tick, Amblyomma americanum, which is confined to North America. Ticks such as Ixodes ricinus – the sheep or deer tick in Europe – can also be associated with alpha-gal syndrome, but the frequency in which this happens is considerably less than for the Lone Star tick. Alpha-gal syndrome is exceptionally rare in the UK.
The syndrome appears to be linked to human genetic factors, but diet and alcohol consumption have also been implicated. Usually, only one type of red meat (beef, lamb or pork) is involved, varying by person.
Symptoms
Symptoms usually start 2 to 6 hours after consumption of red meat by an affected individual, although sometimes may start more rapidly.
Symptoms can include:
- a rash
- urticaria (widespread itching and rash)
- gastrointestinal symptoms including bloating and abdominal discomfort
- anaphylactic reaction (swelling, difficulty breathing, shock)
Testing
Alpha-gal syndrome is diagnosed by a blood testing looking for specific IgE production.
Patients with suspected alpha-gal syndrome should be referred to an allergy specialist to confirm alpha-gal syndrome and to test which meat and meat products the patient should avoid.
It is important to use an NHS accredited laboratory for testing (NHS immunology centres have access to this service). Skin testing is not appropriate and should not be used to diagnose this condition.
The following laboratories are some examples of those that offer testing for alpha-gal IgE:
Other major allergy units can also offer this service so patients should seek guidance from their local specialist unit.
Treatment
The mainstay of treatment is to avoid the specific meat that triggers the reaction. Many reactions resolve on their own, but for (the rare) severe cases treatment for anaphylaxis, including Epipens for adrenaline injection may be needed. Emergency department and first responders such as ambulance crew are trained to manage acute anaphylaxis.
Although the initial sensitisation to alpha-gal comes from the saliva of the tick bite, it is consumption of a red meat product that causes the illness in allergic individuals. Careful inspection of the labelling of processed meat products by affected individuals is important to make sure that the relevant type of meat is avoided.