Objectives
Anthelmintic resistance (AR) in gastrointestinal nematode (GIN) parasites of ruminant livestock has been widely reported in Africa but analysis of variation between regions and over time is lacking. The objective of this paper was to collate data on AR and, through meta-analyses, identify patterns in its occurrence in order to guide future research, practice and policy.
Research design and methods
A systematic literature review following PRISMA guidelines retrieved publications on AR, from which comparable data on treatment effectiveness using the faecal egg count reduction (FECR) test were extracted for meta-analysis using logistic and linear regression.
Results
Data were skewed towards East Africa and small ruminants and spanned 1995-2025. Of 646 articles identified, 60 were retained for analysis. There was evidence of failure across all drug groups: percent FECR (FECR%) was below 95% in sheep and goats in 48% of tests using benzimidazoles (BZ), and 57% for imidazothiazoles (IMTZ) and macrocyclic lactones (ML); in cattle, similar levels of treatment failure were reported but sample size was very low. FECR<95% was more commonly reported in sheep in southern and North Africa than in other regions, and in goats failure rates were higher for BZ and IMTZ than other drug groups and increased over time. FECR% declined in small ruminants over the reporting period for all drug groups and frequently involved survival of Haemonchus after treatment.
Conclusions
Treatment failure due to AR appears to be widespread in ruminant livestock in Africa. This first meta-analysis shows increasing levels of AR over time for the three major anthelmintic drug groups in small ruminants, and similar levels of AR in GIN in cattle. These findings reinforce the need to adapt parasite control strategies to preserve anthelmintic efficacy. They also provide a baseline for future studies, which would benefit from clear and comparable methods for measuring AR and new in vitro technologies.
