Evaluation of Strategies to Reduce Equine Strongyle Infective Larvae on Pasture and Study of Larval Migration and Overwintering in a Nordic Climate

Abstract

Horses, as grazing animals, are inadvertently exposed to intestinal parasites that, if not controlled, may cause disease. However, the indiscriminate use of anthelmintic drugs has led to drug resistance, highlighting the need for pasture-management practices to reduce the level of parasitic exposure and lessen reliance on drugs. The efficacy of such methods depends both on the epidemiology of the parasites and the prevailing weather conditions. The aim of the study was to investigate the effect of faecal removal and harrowing on reducing the number of parasite larvae in herbage. Moreover, the migratory and survival ability of strongyle larvae in a Nordic climate was studied. Faeces from horses naturally infected with strongyle nematodes were used to contaminate pastures and grass samples were collected to harvest larvae. Twice-weekly faecal removal significantly reduced larval yields, whereas harrowing on a single occasion under dry weather conditions in the summer did not. Strongyle larvae were able to migrate 150 cm from the faecal pats, but most larvae were found within 50 cm. Both Cyathostominae and S. vulgaris survived the winter months with larvae harvested up to 17–18 months after faecal placement. Resting of pastures for one year greatly reduced the parasite level, but two years of rest were required for parasite-free pasture.

Survey on sanitary practices and knowledge about infectious diseases among equine owners in the State of Rio Grande do Norte, Brazil

“…Although the use of anthelmintics has reduced the prevalence of the pathogenic parasite Strongylus vulgaris to low levels, it has also led to the development of anthelmintic resistance in Cyathostominae and Parascaris spp. This highlights the need for a shift towards more sustainable control approaches that limit or prevent the development of resistance ( Osterman-Lind et al, 2022 ).…”

“…To limit the use of anthelmintic drugs, alternatives, such as proper fecal and pasture management methods, should be employed to minimize horse exposure to intestinal parasites ( Osterman-Lind et al, 2022 ). The present study demonstrated that 89.53% of the owners discarded the feces removed from the stalls in the paddock or in the equine living environment, without any other management being carried out.…”

“…This can result in contamination of the pastures by nematodes and a vicious cycle of infection, which can culminate in the indiscriminate use of anthelmintics in parasitic resistance. In a recent study, Osterman-Lind et al (2022) demonstrated that by maintaining clean pastures by removing feces twice a week, a previously parasite-free pasture can remain almost completely free of infective larvae for a five-week grazing period or longer up to three months.…”