New Insights on Tick Bites: The Threat of "Meat Allergy" Beyond Just Infections

Table of Contents

1. Introduction: Understanding the Dual Threat Correctly

2. Tick Ecology and Distribution Expansion: Boosted by Warming

3. Tick-Borne Infectious Diseases: SFTS, Japanese Spotted Fever, Lyme Disease

4. What is α-Gal Syndrome (Meat Allergy)?

5. Mechanism of Onset: α-Gal Glycan, IgE, and Delayed Food Allergy

6. Global and Japanese Epidemic Situation: The Misunderstanding of "Only Japan?"

7. Symptoms, Diagnosis, Treatment, and Remission

8. Impact on Lifestyle: Effects on Eating Habits, Medicines, and Daily Goods

9. Risk Factors and Preventive Measures: "Don't Get It, Don't Bring It, Remove It Quickly"

10. Research Frontline: Vaccine Development and Glycan-Modified Foods

11. Frequently Asked Questions (FAQ)

12. Conclusion
    
    

1. Introduction: Understanding the Dual Threat Correctly

Since 2013, the cumulative number of domestic SFTS patients reached 1,071 by the end of April 2025, with a fatality rate fluctuating around 10-30% id-info.jihs.go.jp. Meanwhile, the delayed food allergy triggered by tick bites, known as α-Gal Syndrome (AGS), is increasing globally, imposing lifestyle constraints entirely different from infectious diseases. It is necessary to address both infectious disease and allergy countermeasures in tandem.

2. Tick Ecology and Distribution Expansion: Boosted by Warming

2-1 What are Ticks?

Belonging to the order Acarina of the class Arachnida, ticks feed on the blood of vertebrates at all stages: larvae, nymphs, and adults. In Japan, more than 40 species, including Haemaphysalis longicornis and Ixodes persulcatus, have been identified, with several species involved in the transmission of pathogens to humans. They ambush at the tips of trees and undergrowth, attaching to mammals and humans to start feeding.

2-2 Northward Distribution

According to the Ministry of the Environment's climate change impact assessment, a 3 °C increase in average temperature could expand the habitat of arthropods northward and to higher altitudes, and tick distribution is no exception env.go.jp. There are also survey reports of increased tick captures in the 1,500 m elevation zone of central Honshu and southern Tohoku.

2-3 Risk in Urban Suburbs

Deer and wild boars are more likely to appear in urban areas, bringing ticks as "companions." Opportunities for human bites are increasing with pet walks and gardening activities.

3. Tick-Borne Infectious Diseases: SFTS, Japanese Spotted Fever, Lyme Disease

• SFTS: Transmitted by ticks (mainly Ixodes persulcatus) carrying the SFTS virus. There have been 117 domestic deaths (as of April 2025) id-info.jihs.go.jp.

• Japanese Spotted Fever: A rickettsial infection. 200-300 cases reported annually.

• Lyme Disease: Sporadic in Hokkaido, Nagano, Yamagata, etc. Although fewer reports than in Europe and the US, an increase is expected with warming.
  
  
  
  

4. What is α-Gal Syndrome (Meat Allergy)?

AGS is characterized by the production of IgE antibodies against the tick saliva-derived glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal), causing urticaria, abdominal pain, diarrhea, and respiratory distress 3-6 hours after consuming mammalian meat. First reported by Professor Platts-Mills and colleagues at the University of Virginia in 2009, it has been confirmed in over 17 countries pmc.ncbi.nlm.nih.gov.

5. Mechanism of Onset: α-Gal Glycan, IgE, and Delayed Food Allergy

1. Bite: Ticks inject α-Gal along with saliva.

2. Sensitization: Skin immunity becomes Th2 dominant, producing IgE.

3. Ingestion: Consumption of α-Gal containing foods such as meat, gelatin, and dairy products.

4. Delayed Reaction: Systemic allergy 3-6 hours after eating. The slow circulation of chylomicrons, involved in lipid transport in muscle tissue, is considered the key to the "delayed" reaction sciencedirect.com.
   
   
   
   

6. Global and Japanese Epidemic Situation: The Misunderstanding of "Only Japan?"

• United States: From 2010 to 2022, there were 110,229 suspected cases, with an estimated maximum of 450,000 potential patients cdc.gov. A June 2025 report warned of the expansion of the Lone Star tick to the northeast due to the climate crisis, putting "millions at risk" theguardian.com.
  
  

• Australia: Reported cases of AGS in children from ticks on Kangaroo Island.
  
  

• Europe: Increasing cases in Germany, Spain, Sweden, etc. A 2024 review estimated "thousands to tens of thousands of cases" across Europe.
  
  

• Japan: Case reports are limited to about 10, but the lack of insurance-covered test items makes statistics difficult to capture. A remission case was reported by Kochi University School of Medicine in 2024, suggesting the usefulness of accurate avoidance guidance.
  
  
  

Key Point: The epidemic is common worldwide. The low reporting in Japan is more likely due to "not being visible" rather than "being few."

7. Symptoms, Diagnosis, Treatment, and Remission

7-1 Main Symptoms

Urticaria, angioedema, abdominal pain, diarrhea, vomiting, wheezing, hypotension. Fever is rare.

7-2 Diagnosis

• Interview: History of tick bites + delayed symptoms after consuming red meat.

• Testing: Serum α-Gal specific IgE (>0.35 kUA/L), skin tests often yield false negatives.

• Challenge Test: Gradual intake under hospitalization.

7-3 Treatment

• Acute Phase: Self-injection of epinephrine, H1/H2 blockers.

• Chronic Phase: Elimination of α-Gal containing foods, tick avoidance.

7-4 Remission

Reports exist of meat reintroduction being possible 3-5 years later due to decreased IgE from tick avoidance wwwnc.cdc.gov.

8. Impact on Lifestyle: Effects on Eating Habits, Medicines, and Daily Goods

Not only red meat but also gelatin-containing jelly candies, marshmallows, vaccine adjuvants, animal-derived heparin, and some toothpastes require attention. Efforts to maintain nutritional balance through vegetarianism or a diet centered on chicken and fish are needed.

9. Risk Factors and Preventive Measures: "Don't Get It, Don't Bring It, Remove It Quickly"