Molecular Epidemiology of Human Brucellosis

Abstract

Brucellosis in humans is one of the most important zoonotic diseases worldwide, causing serious public health and economic burdens. This study determined the prevalence of human brucellosis in different occupational groups in Erbil Governorate, Iraq, and evaluated serological, bacteriological, and molecular approaches for detecting Brucella spp. In total, 300 blood samples were collected from six occupational groups (herder families, farmer families, clinical patients, restaurant chefs and staff, butchers, and bakers) between April-November 2024. Samples were tested using Rose Bengal test (RBT), enzyme-linked immunosorbent assay (ELISA), blood culture, and polymerase chain reaction (PCR) targeting the bvrR and bvrS virulence genes. Data were analyzed using the Statistical Package for the Social Sciences, with p < 0.05 considered statistically significant. Overall positivity rates were highest for RBT (10.3%), followed by ELISA (7.0%), while blood culture and PCR each detected 16 positive cases (5.3%). Herder families showed the highest positivity rates; farmer families were positive only for RBT. ELISA positivity was significantly associated with occupation, while RBT and PCR showed borderline significance. RBT and ELISA positivity were significantly higher among rural than urban residents, with no significant association with age or gender. Phylogenetic analysis of bvrR and bvrS sequences showed close clustering with reference Brucella strains in GenBank, with sequence identities of 99.75–100% for bvrR and 99.05–100% for bvrS. Sequences were deposited in GenBank under accession numbers PZ165384 PZ165399 and PZ204958-PZ204973. Our findings highlight burden of brucellosis in animal-exposed populations and the utility of serology and molecular tools for disease surveillance and diagnosis.