Molecular Characterization, SNP-Based Strain Profiling, and Seroprevalence of Bacillus anthracis in Ruminants in...

Anthrax is an endemic and undercharacterized zoonotic disease in the Middle East, including Jordan. Between 2018 and 2020, we conducted a comprehensive investigation of 13 confirmed anthrax outbreaks in Jordan, analyzing 822 samples from animal farm environments, including carcasses, asymptomatic livestock, and abiotic environmental surfaces. All samples were tested by qPCR targeting the chromosomal marker (ba177) and the plasmid marker pXO1 (pag). Among carcass samples, 75/195 (38.5%) were ba177-positive, of which 81% harbored the pXO1. Of specimens from live-animals and from environmental surfaces, 218/627 (35%) were positive by qPCR, likely reflecting environmental contamination during active outbreak periods. Serological analysis using anti-protective antigen (PA) ELISA revealed a high seroprevalence of 53% (75/141) among asymptomatic animals, indicating widespread sub-clinical exposure to B. anthracis antigens and previously undocumented endemicity. An integrated approach combining qPCR with ELISA demonstrated that 11% of seropositive animals with paired swab testing also yielded swab samples that were positive by qPCR, suggesting environment-to-host transition. Molecular strain typing using canonical SNP (canSNP) analysis identified the rare sublineage C.USA.A1055 within lineage C.Br.A1005 across two distinct outbreaks, suggesting the environmental persistence of this endemic lineage. Overall, our findings provide the first systematic molecular and serological surveillance baseline data for Jordan, demonstrating a complex genomic persistence and subclinical exposure landscape. This study suggests the need for enhanced surveillance strategies under the One Health framework to mitigate the risk of anthrax endemicity.