Molecular characterization of Echinococcus granulosus isolated from cattle using multilocus genetic markers in Al-Diwaniyah City, Iraq

Cystic echinococcosis is a major zoonotic parasitic disease that affects livestock and public health worldwide.

This study aimed to molecularly characterize Echinococcus granulosus from cattle using multilocus polymerase chain reaction (PCR) and deoxyribonucleic acid (DNA) sequencing from Al-Diwaniyah City, Iraq, to understand the unique local variants.

An examination of 150 slaughtered cattle was conducted in an abattoir in Al-Diwaniyah, Iraq, from January to June 2024. Thirty cattle had fertile hydatid cysts. One cyst was collected from each of the 30 cattle. The germinal layers were used to extract the processed DNA. TEN representatives were analyzed through multilocus PCR and sequenced for ACT-2, cytochrome c oxidase subunit 1 (COX1), cytochrome b (CYT), and NADH dehydrogenase subunit 1 (ND1). This was followed by BLAST and phylogenetic analysis.

Of the 150 inspected cattle, 30 (20.0%) weighed livestock had viable hydatid cysts, and one cyst was harvested per livestock. Multilocus PCR had a success rate of 100% (10/10) for four selected markers (ACT-2, COX1, CYT, and ND1) in the respective isolates. When sequenced, the isolates' nucleotides matched the global references for E. granulosus within the range of 94.96%-99.61%(mean = 96.95%) for ACT-2, 94.87%-98.72% (mean = 96.41%) for COX1, 99.54%-100% (mean = 99.73%) for CYT, and 96.58%-100% (mean = 98.93%) for ND1. Based on the individual marker sequences, phylogenetic construction of the Iraqi cattle isolates clustered them in the E. granulosus sensu stricto complex (G1-G3) with trace amounts of polymorphisms, evidencing a potential for regionally endemic low-diversity haplotypes.

This study shows that cattle in Al-Diwaniyah Province, Iraq, have E. granulosus sensu stricto genotypes (G1-G3) that suggest the presence of local variants despite having overall high sequence similarity and some divergence, particularly at the COX1 locus. The Iraqi cattle isolates being in the same cluster as the regional and global reference strains indicates that the isolates share transmission lineages and have not undergone divergent evolution. This study corroborates the epidemiological finding that cattle are intermediate hosts in dog-mediated transmission cycles and offers country-specific molecular evidence to support the One Health surveillance and control strategies in Iraq.