Risk factors for α-Gal syndrome: A case-control study exploring the role of tick bites in French Guiana.
α-Gal Syndrome (AGS) is an IgE-mediated allergy to galactose-α-1,3-galactose (α-Gal), a carbohydrate found in non-primate mammalian tissues. AGS manifests as delayed anaphylactic reactions following the consumption of mammalian meat or exposure to products containing α-Gal. Recent studies confirm tick bites may be a key sensitizing factor. This study aimed to investigate tick bites and other potential risk factors for AGS in French Guiana. A retrospective case-control study was conducted at the Cayenne Hospital Center between January 2021 and October 2022. Cases were defined as adults with clinical symptoms of anaphylaxis after consumption of mammalian meat or α-Gal-containing products, and with detectable anti-α-Gal IgE (> 0.1 kUA/L). Controls were patients consulting for other IgE-mediated allergies, without any symptoms after mammalian meat consumption. Data were collected through a standardized questionnaire and specific IgE assays. Bivariate and multivariate analyses were performed to identify associated risk factors. Confounding biases were limited using a propensity score. A total of 54 patients (18 cases, 36 controls) were included. All AGS cases reported at least one tick bite in French Guiana, versus only 22% of controls (Adjusted OR = 170.250; 95% CI [5.981 - 3.528 × 10^6], p < 0.001). Blood group B or AB was less frequent in cases (0% vs 19%, AOR = 0.227; 95% CI [0 - 8.899], p = 0.488). Atopy was not associated with AGS. In this tropical setting, tick bites, especially from the more anthropophilic Amblyomma cajennense sensu stricto, appear to be a major risk factor for AGS, along with forest-related occupational exposure. These findings support the assumption that ticks are probably at least the main vector of symptomatic sensitization to α-Gal in French Guiana.