Screening household members of acute brucellosis cases in endemic areas and risk factors for brucellosis

Abstract

Early diagnosis and treatment of acute brucellosis cases were targeted by screening the household members of the index cases. We also aimed to describe the causal relations of brucellosis in an endemic region. A cross-sectional study was performed among household members (29 index cases, 113 household members). Brucellosis was diagnosed on the basis of clinical findings, serum agglutinin titer of >= 1/160 in standard tube agglutination test (STA), or a positive blood culture. Index cases were defined as patients who had been admitted to the clinic on suspicion of brucellosis and then confirmed as brucellosis cases. The people who lived in the same house as the index cases were defined as household members. The risk factors for seropositivity were studied by multivariate analysis. Independent variables of gender, consuming fresh cheese, blood groups, dealing with husbandry, and contact with the placenta of infected animals were included to the model. Backward and forward selections were performed. Nineteen out of 113 (17%) screened individuals had agglutination titers >= 1/160. The mean ages of index cases and household members were 43 years (standard deviation [SD] 18) and 29 years (SD 19), respectively. In multivariate analysis, consuming fresh cheese (odds ratio [OR]=3.1, confidence interval [CI] 1.07-9.68, p=0.049), blood group A (OR=2.6, CI 1.18-5.96, p=0.018), contact with the placenta of the infected animals (OR=3.7, CI 1.42-9.68, p=0.007), and age >30 years (OR=2.8, CI 1.25-6.51, p=0.13) were found to be associated with brucellosis. In univariate analysis, the individuals with blood group B were protected from brucella infection (p=0.013). In conclusion, screening of the people in brucellosis-endemic areas should be considered for early diagnosis and treatment. To our knowledge, blood groups were studied for the first time by this study. Higher prevalence of brucellosis among the individuals with blood group A and less prevalence among the individuals with blood group B should be considered for further studies on pathogenesis.