The infection cases of Haemonchus contortus are hindering the productivity of ruminant livestock in Indonesia. This issue is exacerbated by the high incidence of resistance due to the use of chemical drugs. This study aimed to evaluate the anthelmintic activity of aqueous extracts of seed [AES] of S. mahagoni seeds against Haemonchus contortus. Separate petri dishes (50 mm) were prepared with AES of S. mahagoni at concentrations of 0 (control negative), 5 and 10%, alongside albendazole (2 mg/ml) as the positive control. Twenty H. contortus worms were then placed in each dish and incubated at 37°C for 0.5, 1, 2, 3, 4, 5, 6, and 12 hours. Mortality of the worms was confirmed by pressing their bodies with tweezers and immersing them in lukewarm water for 5 minutes to ensure death. The time of mortality for each worm was recorded. Subsequently, scanning electron microscopy (SEM) was used to observe the parasites at an accelerating voltage of 15 Kv. Statistical analysis was conducted using SPSS 21.0 software, and descriptive analysis of the standard error of mean was performed. The qualitative analysis of the AES of S. mahagoni revealed the presence of active compounds such as tannin, flavonoid, alkaloid, saponin, and steroid, while quantitative analysis showed total phenol content of 11.7 mg GAE/g dw, flavonoid content of 5.3 mg RE/g dw, and total tannin content of 8.9%. The results indicated that the aqueous extract of Swietenia mahagoni seeds exhibited significant anthelmintic activity, achieving 100% mortality in the in vitro test against H. contortus after 6 hours, compared to the positive control which required (2 mg/ml) after 2 hours. SEM analysis revealed damage to the buccal area and cuticle structure of the worms treated with AES of S. mahagoni. The conclusion of this study is that the AES of S. mahagoni successfully kills H. contortus effectively and could serve as a solution to the prevalent issue of resistance.
