GenBank-derived global inventory of benzimidazole resistance markers in the Haemonchus contortus β-tubulin 1 gene.

Haemonchus contortus is a highly pathogenic gastrointestinal nematode of ruminants and a major cause of production losses in small livestock systems. Its rapid life cycle and blood-feeding habit make it one of the most damaging helminths affecting sheep and goats worldwide. Control relies mainly on anthelmintics, particularly benzimidazoles, macrocyclic lactones, and levamisole; however, resistance to these drug classes has become widespread. Benzimidazole resistance in H. contortus is strongly associated with mutations in the β-tubulin 1 gene, particularly at codons 167, 198, and 200. In this study, all publicly available H. contortus β-tubulin 1 sequences deposited in GenBank (n = 439) were compiled and screened for resistance-associated variants. Records were retrieved programmatically using Biopython and organized within a structured SQL/MariaDB database for downstream analysis. Multiple sequence alignment was performed using ClustalX and verified in BioEdit. After excluding sequences lacking complete coverage of the three target codons, 270 sequences were retained for analysis. Within this GenBank-derived dataset, 38.9% of analyzed sequences contained at least one resistance-associated substitution, reflecting the composition of available database records rather than true field prevalence. Double mutations were rare and no triple mutations were detected. Patterns observed within the available GenBank dataset showed variation across recorded collection years, countries, and host species. Among sequences with geographic metadata, resistant alleles were most frequently observed in records from Brazil and the United States, while many sequences lacked location or host information. Within the available GenBank dataset, host-associated summaries indicated higher proportions of resistance markers among sequences derived from goats and sheep compared with cattle and buffalo. These results provide a systematic overview of benzimidazole resistance markers present in publicly available H. contortus β-tubulin 1 sequences. Because GenBank submissions are not based on systematic field sampling, the observed patterns should be interpreted as database-derived summaries rather than estimates of true global prevalence.