Toward controlling Anaplasma marginale in cattle: Molecular prevalence and risk factors across different climatic...

Bovine anaplasmosis, caused by Anaplasma marginale, poses a significant threat to cattle health and productivity in Iran. This study investigated the molecular prevalence and associated risk factors of A. marginale across four climatic zones in Iran. A cross-sectional design with multi-stage stratified sampling was utilized. Blood samples from 1952 clinically healthy cattle were analyzed using nested-PCR targeting the msp4 gene. The overall prevalence was 23.2 % (95 % CI: 21.3-25.0), with considerable regional variation; it was highest in the Persian Gulf zone at 44 % and lowest in the Caspian zone at 10.5 %. Sub-desert regions exhibited the highest infection rates (44.2 %), while mountainous and plain areas showed lower prevalence (26.1 % and 20.6 %, respectively). Phylogenetic analysis of 16S rRNA sequences revealed distinct clustering of Iranian isolates, suggesting potential genetic divergence from global strains. Key risk factors identified through multivariable logistic regression included grazing practices (OR = 2.02, P = 0.029), inadequate barn sanitation (OR = 2.35, P = 0.002), infrequent ectoparasiticide application (OR = 2.92, P < 0.001), proximity to other farms (OR = 3.12, P = 0.001), and co-rearing with other livestock species (OR = 2.73, P = 0.036). Seasonal variation was notable, with higher infection rates during warm, dry periods (OR = 2.86, P < 0.001). Spatial analysis using SaTScan, configured to identify non-overlapping clusters, revealed four statistically significant clusters, including high-risk clusters in central (Semnan Province, RR=3.88) and southwestern (Khuzestan Province, RR=2.26) Iran, and a low-risk cluster in the Caspian zone (P < 0.001). These findings provide critical evidence for designing targeted surveillance and control programs. The identified high-risk clusters and modifiable risk factors, such as tick control, barn sanitation, and injection practices, offer a clear framework for veterinarians and farmers to prioritize interventions. For policymakers, this study underscores the necessity of region-specific strategies and farmer education campaigns to mitigate the economic and health impacts of bovine anaplasmosis in Iran.