Abilene Reporter-News July 30, 2013
By Drs. David Niesel and Norbert Herzog
Medical Discovery News
Using bug spray is more important than ever – especially for those who particularly enjoy eating hamburgers. It might sound like those two things aren’t related, but a person bitten by a certain tick can develop a severe allergy to meat.
This type of food allergy only develops in people who have been bitten by the Lone Star Tick, which has previously been linked to a condition known as Southern Tick Associated Rash Illness. The tick bite that causes this illness results in a rash, fatigue, headache, fever and muscle pains. It is often confused with Lyme disease, which is also spread by ticks.
After being bitten by the Lone Star Tick, a person develops antibodies — molecules of the immune system that normally target and destroy invaders like viruses and bacteria — against a complex sugar called galactose-alpha-1,3-galactose (alpha-gal). This sugar exists in all mammals except primates, including cows, pigs and sheep. This specific allergy has a delayed response, so a person would experience symptoms like hives four to six hours after eating a meat such as bacon. Some people even suffer life-threatening anaphylactic shock.
It is unclear what in tick saliva triggers alpha-gal antibody production. When ticks latch on to people with their mouthparts they can remain attached for several days and introduce saliva into the skin at the bite site. Tick saliva contains molecules that keep the tick firmly attached to its host. It also keeps the blood at the site from clotting, so the tick can continue its meal and can influence the immune response and angiogenesis, the development of new blood vessels. In addition, ticks can transmit a variety of viruses and bacteria through their saliva.
This allergy first came to light because some cancer patients were unusually sensitive to the cancer drug cetuximab, which includes the alpha-gal molecule. Only patients from the southeastern and eastern United States, where the Lone Star Tick lives, experienced this, and they all had high levels of alpha-gal antibodies. Currently, more than 80 percent of the people with this meat allergy had tick bites before exhibiting symptoms.
But now that cases of this meat allergy have been reported outside the Lone Star Tick’s habitat, such as Hawaii, researchers are wondering whether this tick has spread further than they thought, or if other tick species can cause a similar reaction. The Lone Star Tick is very aggressive when it comes to biting people and animals, so to prevent tick bites use a bug spray with permethrin, avoid wooded areas and frequently check for ticks when outside. Otherwise, you may find yourself watching everyone else eat during a summer barbecue!
Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com.