Evidence of multiple anthelmintic resistance amongst dorper sheep with phenotypic markers against parasitic gastroenteritis in a selected farm in Perlis

Parasitic gastroenteritis is a notable disease that has major impacts on small ruminant production. The infection is managed primarily reliant on the use of chemical anthelmintics. Nevertheless, the effectiveness of this approach is limited by the emergence of anthelmintic resistance. Therefore, it is imperative to reduce reliance on anthelmintics. The objective of this study was to assess the anthelmintic resistance status of a Dorper sheep farm under a semi-intensive system. Besides, this study also aimed to identify the phenotypic markers of resistance to parasite infection. Eighty sheep were screened for the criteria of Faecal Egg Count Reduction Test (FECRT) by using Modified McMaster method. Fifty-eight out of 80 sheep were identified as having faecal egg counts (FEC) exceeding 150 eggs per gram (epg). These sheep were segregated into five groups, comprising a control group and four anthelmintic treatment groups namely albendazole, fenbendazole, levamisole and ivermectin. Each group consisted of 11 to 13 animals with an average mean of FEC for each group were approximately similar ranging from 979 to 1295 epg. The dosages and modes of administration of the anthelmintics were administered in accordance with the guidelines provided by the manufacturer. The second faecal sample was taken after 14 days for post-treatment FEC. The faecal samples of pre- treatment and post-treatment were also analysed for infective stage larvae (L3) identification to genus level by faecal culture and species confirmation through polymerase chain reaction (PCR). Moreover, blood samples were also collected before and after treatment for packed cell volume (PCV) and peripheral eosinophil counts (PEC). A Spearman rank correlation analysis was conducted to examine the associations between the means of FEC, PCV, and PEC for each group. Non-parametric statistical tests of Kruskal-Wallis and Wilcoxon rank sum were employed to analyse the significant differences of FEC and PEC in various groups. Parametric data of PCV was evaluated by a two-way ANOVA followed by a post-hoc test of Tukey Honest Significant Differences (HSD).. The FECRT results indicated severe to critical degree of resistance to albendazole (52%), levamisole (88%), fenbendazole (43%), and ivermectin (-45%) have been developed in this farm. Pre-treatment and post-treatment faecal culture revealed that the most prevalent genus of infective stage larvae (L3) infecting the sheep in the farm was Haemonchus contortus at 88% and 81% respectively. Findings from both pre-treatment and post-treatment showed significant negative correlations between FEC and PCV in the control, fenbendazole and ivermectin groups at r(103) = -.86, -.72, and -.78 (p=0.010) respectively for pre-treatment and r(103) = -.88, -.58, -.69 (p = 0.010) respectively for post-treatment. Additionally, significant positive correlations were observed between FEC and PEC during the pre-treatment of levamisole group at r(103) = .63 (p = 0.010) as well as during post-treatment of the control and levamisole group at r(103) = .95 (p= 0.010) and r(103) = .56 (p = 0.050), respectively. In conclusion, the present study reveals the existence of multiple anthelmintic resistance in the farm with potential existence of resistant traits of Dorper sheep against gastrointestinal parasite infections.