Association Between Serological Responses to Two Zoonotic Ruminant Pathogens and Esophageal Squamous Cell Carcinoma

Questionnaire data have linked contact with ruminants to the risk of esophageal squamous cell carcinoma (ESCC) in high-risk Asian populations. To better understand this observed association, we investigated exposure to two major zoonotic ruminant pathogens relative to ESCC risk. Using enzyme-linked immunosorbent assay, immunofluorescence assay, and Brucella microagglutination test assays, we measured immunoglobulin G anti-Coxiella burnetii and anti-Brucella spp. antibodies in patients with ESCC (n = 177) and population-based controls (n = 177) matched by age, gender, and residence area from the Golestan case-control study in Iran. We found a similarly high seroprevalence of C. burnetii in ESCC cases and controls (75% and 80%, respectively), and a similarly low seroprevalence of Brucella spp. (0% and 0.6%, respectively). While documenting a high exposure to one of two zoonotic ruminant infections, this exposure failed to explain the observed association of ruminant contact and ESCC risk in this high-risk population.