Role of zinc oxide nanoparticles in the parasitism and abomasal pathophysiology of lambs artificially infected with Haemonchus contortus.

Haemonchus contortus is a major gastrointestinal nematode affecting sheep and causing substantial economic losses. Nutritional strategies like zinc supplementation may enhance host resilience and immune responses. This study evaluated the effects of zinc oxide microparticles (ZnO-MC) and nanoparticles (ZnO-NP) on parasitological, histopathological, and mucosal responses in infected lambs. Fifty-nine Santa Ines lambs were allocated into three groups: unsupplemented control, ZnO-MC, or ZnO-NP. Infected animals received 1200 H. contortus L3 weekly for 24 weeks. Parasitological parameters, weight gain, histopathology, mucosal thickness, PAS staining, and abomasal cell infiltration were evaluated. ZnO-NP showed the lowest numerical means for all parasite developmental stages and reduced the number of adult females (p = 0.0382), though total worm burden, worm length, and eggs per female did not change significantly. Infection was the main factor associated with histopathological changes, including inflammatory infiltration and increased mucosal thickness. Although ZnO supplementation did not significantly alter the cumulative histopathological score, supplemented lambs showed a lower frequency of severe lesions and less mucous cell atrophy. ZnO-MC showed increased PAS reactivity (p = 0.0346), whereas ZnO-NP showed the lowest PAS reactivity. Infection also increased eosinophil and globular leukocyte counts, with ZnO-MC associated with higher eosinophil counts (p = 0.0469) and ZnO-NP with higher globular leukocyte counts (p = 0.0263). Overall, ZnO supplementation, mainly ZnO-NP, may contribute to modulating the local immune response and partially preserving abomasal mucosa integrity during H. contortus infection in lambs, representing a useful supportive nutritional measure within integrated control programs for haemonchosis in sheep.