Predatory activity of Macrochelidae mites (Acari: Mesostigmata) against larvae of Haemonchus contortus (Strongylida: Trichostrongylidae) under field conditions

The gastrointestinal nematode Haemonchus contortus (Rudolphi, 1803) is the most prevalent endoparasite in sheep worldwide, causing serious economic losses due to resistance to commercial anthelmintics, which necessitates alternative and sustainable control strategies. Biological control using predatory mites, naturally present in the environment, emerges as a promising approach. This study evaluated the predatory activity of two mite species, Macrocheles merdarius (Berlese, 1889) and Holostaspella bifoliata (Trägårdh, 1952), on H. contortus larvae under simulated field conditions in Brachiaria sp. pastures. Two independent trials were conducted: in the first, M. merdarius was applied at different densities (12, 25, and 50 mites); in the second, both species were tested individually and in combination. The experimental plots were delimited in 50 cm² quadrants. Larval recovery data (e) were transformed by log₁₀(n + 1) for normalization and analysed using generalized linear models (PROC GLM, SAS), with t-tests for comparisons between treatments and controls (p < 0.05). In the first trial, M. merdarius significantly reduced larval recovery, reaching up to 84% effectiveness at the highest density. In the second trial, H. bifoliata showed the greatest reduction in infective larvae (87.7%), surpassing M. merdarius (56.5%) and the combined treatment (58.5%). It has been shown that both mite species can reduce the population of H. contortus in its free-living stage, and their use can enhance integrated pest management strategies and reduce reliance on chemical anthelmintics.