Vet Watch Update: New tick species implicated in alpha-gal syndrome

Is the lone star tick the only vector for alpha-gal syndrome? New evidence says no, expanding the geographic risk for this serious meat allergy across the United States.

Transcript

Christopher Lee, DVM, MPH, DACVPM: This is a Vet Watch Update at dvm360. I’m Christopher Lee.

Alpha-gal syndrome—new studies have shown that this potentially deadly disease may be transmitted by more than one tick species.

To review, alpha-gal syndrome, or AGS, is a serious meat allergy in people against galactose-alpha-1,3-galactose, a large sugar molecule found in the tissues of nonprimate mammals. People with AGS can no longer eat most mammalian tissue—including beef, pork, lamb, and even rabbit—but they can still eat poultry, seafood, and less common protein sources such as alligator or escargot.

What is unusual about AGS is that it is transmitted through the bite of a tick, namely, Amblyomma americanum, the lone star tick. This tick has an enzyme in its salivary glands, alpha-D-galactosidase, that cleaves alpha-gal from mammalian tissue. How alpha-gal then ends up in the tick’s saliva when biting a person is not fully understood, but we do know that partially fed ticks carry high levels of alpha-gal in their saliva.

Consider this scenario: an A. americanum tick feeds on a dog, mouse, or deer, and its meal is interrupted—perhaps it gets brushed off. Now it’s searching for a new host. It finds a human, climbs up, and begins to bite. With high levels of alpha-gal in its saliva, that molecule gets injected subcutaneously into the person, triggering a strong immune response and an IgE-mediated reaction. If sensitization occurs, that individual will have AGS for life. Within hours of eating pork or beef, they can experience facial swelling, hives, or even life-threatening anaphylaxis.

New reports now show that Ixodes scapularis and Ixodes pacificus, ticks famous for transmitting Lyme disease, may also trigger AGS. This finding expands the geographic risk. Ixodes scapularis is found throughout the eastern half of the United States. The lone star tick’s range overlaps much of this area but does not extend as far north. Ixodes pacificus inhabits the Pacific coast (California, Oregon, and Washington).

So, what do we do with this information? We keep prescribing year-round tick prevention to all of our patients.

Thank you for watching Vet Watch here at dvm360, where what you know today protects everybody tomorrow.