School of Occupational and Public Health, Ryerson University, 350 Victoria Street, Toronto, Ontario, M5B 2K3, Canada.
National Microbiology Laboratory, Public Health Agency of Canada, Guelph, Ontario, N1G 5B2, Canada.
Ticks Tick Borne Dis. 2021 May;12(3):101674. doi: 10.1016/j.ttbdis.2021.101674. Epub 2021 Jan 27.
Alpha-gal syndrome (AGS) refers to a delayed allergic reaction to galactose-α-1,3-galactose (α-Gal) that occurs following the consumption of mammalian meat or exposure to other animal-based foods and products. Increasing evidence suggests that bites from certain tick species can lead to AGS through sensitization of a person's α-Gal specific IgE levels. This systematic review aimed to summarize the published evidence on this topic to understand post-tick exposure AGS epidemiology and health outcomes. A structured search for literature in eight bibliographic databases was conducted in January, 2020. Grey literature and verification searches were also performed. The exposure of interest was tick bites, and the outcome of interest was AGS. All primary research study designs were eligible for inclusion. References were screened for relevance, and data extraction and risk-of-bias assessment were conducted on relevant studies by two independent reviewers. Data were descriptively and narratively summarized. Of 1390 references screened, 102 relevant articles (103 unique studies) were identified (published from 2009 to 2020). Most studies (76.7 %) were case report or series. These 79 studies reported on 236 post-tick exposure AGS cases from 20 different countries, mostly the United States (33.5 %), Spain (19.5 %), Sweden (18.6 %), and France (12.7 %). The mean case age was 51.3 (SD = 16.7, range 5-85, n = 229), while 68.1 % were male (n = 226). The most commonly reported symptom was urticaria (71.2 %); 51.7 % of cases reported anaphylaxis. Twenty-one observational studies were reported, mostly (95.2 %) among clinical allergy patients. The proportion of AGS cases that recalled tick bites was highly variable across these studies. Three challenge studies evaluating tick exposures and α-Gal levels in α-Gal deficient mice were identified. The existing evidence suggests tick bites lead to α-Gal-specific IgE sensitization, which can cause AGS, but further research is needed to clarify if AGS is only attributable to certain tick species and whether other vectors may trigger AGS. Additional research is needed on risk factors for AGS development, evaluation of diagnostic immunoassays, and the epidemiology and distribution of AGS in different populations. Climate change will likely lead to future cases of AGS in new regions worldwide due to the predicted alteration of suitable tick habitats.
α-半乳糖综合征（AGS）是指在食用哺乳动物肉类或接触其他动物源性食品和产品后，机体对半乳糖-α-1,3-半乳糖（α-Gal）产生的延迟过敏反应。越来越多的证据表明，某些特定种类的蜱叮咬可导致 AGS，这是由于个体的 α-Gal 特异性 IgE 水平致敏所致。本系统评价旨在总结该主题的已发表证据，以了解蜱叮咬后 AGS 的流行病学和健康结局。我们于 2020 年 1 月在八个文献数据库中进行了文献的结构化搜索。还进行了灰色文献和验证搜索。感兴趣的暴露是蜱叮咬，感兴趣的结局是 AGS。所有的原始研究设计都符合纳入标准。两名独立评审员对相关研究进行了文献筛选、数据提取和偏倚风险评估。对数据进行了描述性和叙述性总结。在筛选的 1390 篇参考文献中，确定了 102 篇相关文章（103 项研究）（发表于 2009 年至 2020 年）。大多数研究（76.7%）为病例报告或病例系列研究。这 79 项研究报告了来自 20 个不同国家的 236 例蜱叮咬后 AGS 病例，主要来自美国（33.5%）、西班牙（19.5%）、瑞典（18.6%）和法国（12.7%）。平均病例年龄为 51.3（标准差=16.7，范围 5-85，n=229），68.1%为男性（n=226）。最常报告的症状是荨麻疹（71.2%）；51.7%的病例报告有过敏反应。报道了 21 项观察性研究，主要在临床过敏患者中进行（95.2%）。这些研究中，报告蜱叮咬的 AGS 病例比例差异很大。鉴定了三项评估 α-Gal 缺陷小鼠中蜱暴露和 α-Gal 水平的挑战研究。现有证据表明，蜱叮咬可导致 α-Gal 特异性 IgE 致敏，从而引发 AGS，但仍需要进一步研究来明确 AGS 是否仅归因于某些特定种类的蜱，以及其他媒介是否可能引发 AGS。还需要进一步研究 AGS 发展的危险因素、诊断免疫测定的评估，以及不同人群中 AGS 的流行病学和分布。由于预测的合适蜱栖息地的改变，气候变化可能会导致未来世界各地新地区出现 AGS。
