Morphometric diversity of Fasciola gigantica in northern Cameroon and in vitro fasciolicidal activity of Combretum nigricans extracts.

Fasciolosis is a neglected parasitic disease that affects cattle productivity in Northern Cameroon; yet the morphology of local flukes and the fasciolicidal potential of indigenous medicinal plants remain poorly documented. This study examined the morphometry of Fasciola spp. in three Cameroonian regions and the fasciolicidal activity of aqueous extracts of Combretum nigricans, a hepatoprotective plant. From May to August 2024, 4910 flukes were collected from 301 slaughtered cattle across Ngaoundere 2, Garoua Balmari, and Kousseri. Morphometric traits were analyzed according to sampling region, host sex, breed, age, and infestation level. Aqueous leaf, root, and stem bark extracts of C. nigricans were tested ex vivo and compared with Nitroxynil, while biochemical and histological analyses evaluated digestive enzyme integrity, oxidative stress markers, energy stores, and tegument integrity. Fasciola gigantica was the dominant species. Fluke size varied significantly (p < 0.001) with host and geographic factors. Males harbored longer and wider flukes; Bokolo and M'Bororo breeds showed distinct profiles; and heavily infested cattle carried larger flukes (p < 0.001). Flukes from Garoua and Kousseri were generally longer, while those from Ngaoundere were shorter but wider (p < 0.001). Leaf (IC50 = 472 ± 29 μg/mL) and root extracts (IC50 = 656 ± 68 μg/mL) displayed stronger and faster activity than the stem bark extract, but were less potent than Nitroxynil. Both extracts caused tegumental erosion, reduced trypsin activity, depleted triglyceride stores, promoted glycogen accumulation, and enhanced antioxidant responses. With F. gigantica dominating in Cameroon's Northern regions, the flukicidal activity of C. nigricans provides a promising and suitable option for sustainable fasciolosis control.