Anthelmintic Resistance of Gastrointestinal Strongyles Infecting Sheep in Nziih, West Cameroon

Aims: This study aimed to investigate the levels of efficacy of anthelmintics that were most commonly used in sheep farms in Nziih locality.

Study Design: Longitudinal prospective study.

Place and Duration of Study: The study was carried out in Nziih locality in August 2019 and September 2020.

Methodology: Resistance against Albendazole (12.5 mg/kg) and Ivermectin (0.2 mg/kg) was evaluated using faecal egg count reduction test in naturally occurring gastrointestinal strongyles of sheep in Nziih. A total of 300 young animals were randomly selected from 5 farms in 2019 and in 2020. Faecal samples were collected from each animal on the first day of treatment (D0) and collected again 14 days later (D14). Faecal Egg Counts were performed using the Willis and Mac Master techniques and resistance was declared when faecal egg count reduction (FECR) was less than 95 % and the lower limit of confidence interval (LCI) less than 90%. Pooled faecal samples for each treatment group were set for D0 and D14 to identify resistant strongyles genera by calculating persistent larval rate (PLR).

Results: Resistance against Ivermectin was detected while there was none against Albendazole. Moreover, it was declared only in 2 farms out of the 5 selected. From 2019 to 2020, the status of resistance has shifted from suspicion to resistance for ivermectin and from absence of resistance to suspicion to Albendazole. Resistance was recorded in 2 sites: Pastorale1 (FECR= 85 %, LCI= 42.61 %) and Pastorale 3 (FECR=90.5 %, LCI= 72.26 %) in large flock herds and in farms where sheep were dewormed at least 4 times per year. Trichostrongylus were more persistent than Haemonchus and Oesophagostomum/Chabertia with PLR of 21.22 %, 13.71 %, and 7.40 % respectively.

Conclusion: Anthelmintics must be used correctly in conjunction with farmer education in Nziih.