Tick-Borne Illness Triggers Red Meat Allergy in Two Women, CDC Reports
Two women developed a rare tick-borne illness causing severe reactions including vomiting, diarrhea, breathing difficulties, and life-threatening allergic responses, according to a new report.
The women, hailing from Maine and Washington state, had no prior history of food allergies. However, they began experiencing allergic reactions after consuming red meat.
Alpha-Gal Syndrome Diagnosis Following Tick Bites
Medical history revealed that both women had been bitten by ticks in the preceding month. Blood tests subsequently confirmed they had developed alpha-gal syndrome (AGS).
AGS is initiated when a person is bitten by a tick carrying the alpha-gal sugar, most commonly the lone star tick. During a bite, the tick injects this sugar, prompting the human immune system to produce antibodies that target alpha-gal.
Alpha-gal molecules are present in the meat of most mammals, such as beef, pork, venison, and other red meats, as well as in animal products like milk and gelatin.
Upon consuming these foods, the body identifies the alpha-gal and triggers an immune response. This reaction can manifest as a severe, potentially life-threatening allergy.
Rising Concerns Over Alpha-Gal Syndrome Prevalence
Health authorities report no confirmed fatalities from AGS, but express increasing alarm regarding the condition’s expanding reach.
The Centers for Disease Control and Prevention (CDC) documented approximately 90,000 suspected AGS cases between 2017 and 2022. New suspected cases are increasing by around 15,000 annually. Estimates suggest as many as half a million Americans may be affected by AGS.
Alpha-gal syndrome (AGS) is triggered by a tick bite, often from the lone star tick (pictured), which carries the alpha-gal sugar.
Geographic Expansion of Tick-Borne Allergy
While cases were initially concentrated in the southern, midwestern, and mid-Atlantic regions of the US, recent analyses of human and tick samples indicate a broader risk. The tick species responsible for AGS is spreading into new geographical areas, potentially exposing millions more individuals.
Furthermore, research indicates that new tick species are increasingly transmitting the condition to humans.
Case Studies Detail Allergic Reactions
A recent CDC case study described a 61-year-old woman from Washington state who experienced two allergic episodes – one requiring hospitalization – after a bite from an unidentified tick one to two months prior.
Her initial reaction, occurring 29 days post-bite, involved hives and lip swelling.
Symptoms initially subsided with allergy medication. However, a month later, she developed groin itching and back hives.
Her tongue subsequently swelled, and she experienced speech difficulties, prompting a 911 call and急诊 transport to the hospital.
En route, her condition worsened with breathing complications, spreading hives, and increased tongue swelling. A dangerous drop in blood pressure and rapid heart rate ensued.
Epinephrine, standard treatment for allergic reactions, was administered but proved ineffective as her symptoms intensified, and her throat began to close.
Steroids were then administered, and her condition started to improve upon hospital arrival.
Initially, she reported no significant preceding events for either reaction. Later, she recalled a tick bite about a month before the first episode, for which she received antibiotic treatment.
Reported cases of alpha-gal syndrome in the US between 2017 and 2022 are shown in the map above.
Further investigation revealed she had consumed six beef tacos before the first episode and a pork sausage and ham sandwich before the second.
Alpha-gal blood levels, measured in kilounits per liter (kU/L), are used to diagnose AGS. The woman’s levels were 27.4 kU/L. Experts consider any result above 0.1 kU/L as positive for AGS.
She was advised to eliminate red meat and avoid milk and gelatin. Following this dietary change, she experienced no further allergic reactions, and her alpha-gal levels decreased to approximately 7 kU/L.
Approximately three years later, in April 2020, she sustained another bite from a western black-legged tick. Three days after, her alpha-gal levels were 0.72 kU/L, rising to 20 kU/L a month later.
Two years following, another western black-legged tick bite occurred. Shortly after discovery, levels were 0.89 kU/L, increasing to 18.8 kU/L after four weeks.
Case report authors suggested her vegetarian diet protected her from severe allergic reactions despite elevated alpha-gal levels.
Second Case Study: Maine Woman Develops Severe AGS
The second CDC case study detailed a 45-year-old Maine woman who found a deer tick on her arm in May 2022.
Following tick removal, she experienced minor swelling and redness but no immediate adverse effects.
Around ten days later, after consuming roasted rabbit, she developed abdominal pain and fatigue lasting three hours.
Recurrent similar symptoms occurred over the next two weeks every time she ingested red meat.
About three weeks post-bite, a ‘severe’ episode of diarrhea and vomiting after beef consumption prompted a doctor’s visit.
Blood tests revealed alpha-gal levels exceeding 100 kU/L – surpassing the maximum detection limit.
Physicians recommended avoiding pork, beef, and lamb. Dairy was partially tolerated, but foods like ice cream induced nausea and cramps.
Symptoms resolved with the recommended diet. However, she discovered two additional ticks within two months of the initial incident.
Three months later, bacon consumption triggered heartburn, as did steak seven months later.
However, ten months after the initial tick bite, she could consume steak and roast beef without symptoms and resumed eating red meat.
Approximately one year after initial testing, alpha-gal levels decreased to 16 kU/L, and further reduced to 4.6 kU/L at two years.
Importance of AGS Surveillance
Both case report authors emphasized the necessity for heightened surveillance of AGS and the tick species responsible. Ticks and geographic areas not historically associated with AGS are increasingly identified as sources of the condition.