Gastrointestinal trichostrongylosis can predispose ewes to clinical mastitis after experimental mammary infection

•Sheep: role of gastrointestinal nematode infection in predisposing to mastitis was studied.•Gastrointestinal trichostrongylosis might lead to clinical mastitis.•Effect of Teledorsagia helminths was more significant.•Various pathogenetic pathways can be involved. Objective was to study, in an experimental model, the possible role of gastrointestinal nematode infection in predisposing ewes to mastitis during the lactation period. Twenty-four ewes (A or B [n=12]), free from nematode and trematode helminths, were used. Group A animals received 5000 third-stage larvae of a trichostrongylid helminth cocktail and group B ewes were unparasitised controls. Animals in group A developed gastrointestinal trichostrongylosis confirmed by >500epg in faecal samples; mean epg of group B ewes were