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Thanakorn Rompo. Clinical assessment of anthelmintic drug efficacy and resistance in strongyle nematodes of dairy goats in Chiang Mai Province, Thailand. Master's Degree(Veterinary Science). Chiang Mai University. Library. : Chiang Mai University, 2025.
Clinical assessment of anthelmintic drug efficacy and resistance in strongyle nematodes of dairy goats in Chiang Mai Province, Thailand
Abstract:
Gastrointestinal nematodes, particularly strongyles, remain a major constraint to the health and productivity of goats, with increasing concerns over anthelmintic resistance (AR). In Thailand, despite the growing interest in goat production and goat milk products, information on AR is limited, especially in the northern region. On a dairy goat farm in Chiang Mai, a recent field test confirmed ivermectin-resistant strongyle infections following routine blanket treatments. This highlighted the urgent need for alternative treatment options and evidence-based deworming strategies. This study assessed the efficacy of eprinomectin (0.2 mg/kg and 0.4 mg/kg), albendazole (20 mg/kg), and their combination using fecal egg count reduction tests (FECRT), alongside species-specific treatment responses analyzed via nemabiome metabarcoding of the internal transcribed spacer 2 (ITS-2) region. Two sequential clinical field trials were conducted. Goats were randomly assigned to treatment groups or an untreated control. Individually copro-DNA was extracted and sequenced using the Illumina MiSeq platform to identify strongyle taxa and determine their relative abundance. FECRT results, following the interpretation criteria of WAAVP guideline (2023), indicated reduced efficacy and confirmed resistance in all treatment groups. Nemabiome analysis identified seven strongyle taxa, with Haemonchus contortus and Trichostrongylus colubriformis as the predominant species. Despite their increased relative abundance following treatment, species richness and Pielous evenness remained stable, indicating no major change in overall community structure. Species-specific egg count reduction (ECR) analysis revealed poor efficacy against H. contortus and T. colubriformis, whereas T. axei and Oesophagostomum columbianum showed complete or near-complete reduction in some treatment groups. These findings confirm multidrug resistance among strongyle nematodes on a Thai dairy goat farm. However, the continued susceptibility of certain species highlights the importance of species-specific evaluation. The integration of FECRT with nemabiome sequencing provided detailed insights into treatment efficacy, supporting more targeted deworming strategies and reinforcing the value of molecular diagnostics in guiding sustainable parasite control in small ruminant systems.