Molecular detection, seroprevalence, and phylogenetic analysis of Brucella suis in wild pigs (Sus scrofa) in Iraq: Implications for One Health surveillance.

BACKGROUND AND AIM: Brucellosis remains a globally significant zoonotic disease with significant public health and economic implications. While domestic pigs are absent in Iraq due to religious restrictions, wild pigs (Sus scrofa) represent a potential reservoir for zoonotic pathogens, including Brucella suis. Despite this, no prior investigations have assessed the prevalence of swine brucellosis in Iraq. This study aimed to (i) determine the seroprevalence of brucellosis in wild pigs using enzyme-linked immunosorbent assay (ELISA), (ii) evaluate associated risk factors such as age, sex, and region, and (iii) confirm infection and characterize isolates through molecular detection and phylogenetic analysis.

MATERIALS AND

METHODS

Between September 2022 and January 2024, venous blood samples (n = 42) from recently killed wild pigs in Wasit province were analyzed. Sera were screened using ELISA, while DNA was extracted and tested with conventional polymerase chain reaction (PCR) and quantitative real-time PCR (qPCR) targeting the 16S ribosomal RNA gene. Positive isolates were sequenced and compared to reference strains in GenBank using phylogenetic analysis. Statistical associations with risk factors were assessed using odds ratios and relative risk.

RESULTS

ELISA detected anti-Brucella antibodies in 54.76% of samples, with mild (39.13%), moderate (34.78%), and severe (26.09%) infections. Molecular assays revealed B. suis DNA in 33.33% of samples by PCR and 45.24% by qPCR. Seropositivity was significantly higher in pigs aged 2-4 years (73.33%) compared with <2 years (38.1%) and >4 years (66.67%) (p < 0.05). Female pigs exhibited a higher prevalence (57.58%) than males (44.44%), and animals from Al-Numaniyah showed the highest rates (73.68%). Phylogenetic analysis revealed 98.87%-99.76% similarity with Indian B. suis strains (MF173089.1), characterized by minor nucleotide variations.

CONCLUSION

This study provides the first molecular evidence of B. suis in wild pigs in Iraq, underscoring their role as potential reservoirs for zoonotic transmission. The findings highlight the importance of integrating molecular diagnostics with serology for accurate surveillance. Strengthening One Health strategies, including wildlife monitoring, biosecurity, and public health education, is critical to preventing spillover to domestic animals and humans. Further large-scale investigations are warranted to better characterize the epidemiology of swine brucellosis in the region.