It may be new to you, but the Lone Star tick (Amblyomma americanum) was actually the first North American tick species to be formally described, with reports dating back to the late 1700s. The Southeastern, South-central, and mid-Atlantic states are ground zero for this tick, but a 2014 study revealed that Lone Star ticks can now be found as far west as Colorado and Wyoming and as far north as Maine.
Range expansion of the Lone Star tick
While its range is expanding, establishment of Lone Star ticks in new areas is heavily dependent on the correct habitat for host-seeking and development, as well as the availability of preferred hosts. Lone Star ticks require forests with dense undergrowth, and these are environments where their most important host, white-tailed deer, also reside. Researchers suggest that as deer population numbers continue to increase and they expand into suburban and even peri-urban spaces, the Lone Star tick will not be far behind.
Have you seen it?
Adult female Lone Star ticks, the species’ namesake, display a bright yellowish-white dot at the tip of their scutum highlighted on a light brown body. Males (shown here) are also light brown, but their scutums are sometimes mottled with black and a few white streaks along their festoons. Both nymphs and six-legged larvae are brown and round; nymphs have long, straight mouth-parts, while larvae have shorter mouthparts. Be aware that all stages change in appearance and size as they feed.
Adults emerge in the early spring and remain active throughout the summer.
Engorged female Lone Star tick (top and bottom) shown here.
In May they are joined by nymphs (shown here), and in July by tiny larvae. Deer are the first choice for all stages, but they’ll also swarm the legs of humans and pets if given the chance. It is crucial to recognize Lone Stars because they are aggressive biters of humans and domestic animals and carriers of many germs including several types of Ehrlichia, tularemia, an unknown agent that causes southern tick-associated rash illness (STARI), which can mimic Lyme disease, and rarely Heartland virus. Lone Stars do NOT transmit Lyme disease.
Lone Star ticks and red meat allergy (“Alpha-gal”)
A bite from a Lone Star tick can occasionally cause sensitivity to a carbohydrate found on mammalian muscle and tissue cells, commonly called alpha-gal (galactose-alpha-1,3-galactose). The first U.S. reports of this rare phenomenon were made in 1991, when descriptions of delayed reactions to mammalian meat consumption following Lone Star tick bites in the southeastern states were presented to the Centers for Disease Control (CDC) and the Georgia Allergy Society. Since then, cases of a heightened sensitization to red meat as a result of tick bites have also been reported in Australia and Europe.
It is not known whether components of the tick’s saliva or remnants of alpha-gal from previous blood meals are what triggers the allergy. Humans and other primates are the only mammals who do not have this carbohydrate on our muscle cells, so our immune systems can sometimes see it as foreign and mount an overblown response to it with an antibody called IgE. It can sometimes take between 1-3 months after the tick bite before the allergy appears. Once the allergy has developed, a delayed reaction occurs generally 2-6 hours after ingestion of mammalian meat (e.g. pork, beef, lamb – not poultry or fish).
Early symptoms can include gastrointestinal upset (nausea, diarrhea, indigestion) but a reaction is most commonly preceded by itchiness. Mild incidents can include hives and rashes, but more severe reactions can involve anaphylaxis. It is thought that people with blood types B or AB are less likely to develop this severe allergy because they naturally have fewer antibodies to alpha-gal. Conversely, people who experience very itchy, localized reactions to Lone Star bites are more likely to go on to develop the condition. New research suggests, however, that not everyone who has a reaction to red meat acquired it from a tick bite. In a study that included 70 participants who had histories of unexplained and frequent anaphylaxis, only 6 of them tested positive for the IgE antibody, the hallmark of the the tick-induced alpha-gal allergy. While you can be tested for the alpha-gal allergy if you’ve already been bitten by a Lone Star tick, prevention of tick bites is the most important way to avoid this condition all together. Limited evidence has shown that, over time, the allergy can become less severe if a person avoids additional tick bites.
Article written by Heather Kopsco, PhD student, Plant Sciences and Entomology Dept. at URI
Photography: brian mullen
References
1. Springer YP, Eisen L, Beati L, James AM, Eisen RJ. 2014. Spatial Distribution of Counties in the Continental Unitied States with Records of Occurrence of Amblyomma americanum (Ixodida: Ixodidae). J. Med. Entomol. 51(2): 342-351.
2. Steinke J, Platts-Mills T, Commins, S. 2015. The alpha-gal story: lessons learned from connecting the dots. J Allergy Clin Immunol. 135(3): 589-96.
3. van Nunan, S. 2014. Galactose-alpha-1,3-galactose, Mammalian and Anaphylaxis: A Worldwide Phenomenon? Current Treatment Options in Allergy. 1:262–277.
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