OAHN Small Ruminant Network Project: Investigation of mucosal immunity to gastrointestinal nematodes in Ontario goats

Project Lead: Dr. Emma Borkowski

Collaborators: Caitlin Evered (DVSc student), Robert Foster, Andrew Peregrine, Cathy Bauman

Executive Summary

Gastrointestinal nematodes (GINs) are a persistent constraint on small ruminant health and productivity in Ontario. Conventional control of GINs relies on repeated anthelmintic use; however, escalating anthelmintic resistance necessitates investigation of potential immunologic control. This project examined mucosal responses of Ontario goats to GIN parasitism by characterizing salivary antibody responses to carbohydrate larval antigen (CarLA) and associations with age, GIN species, and farm management practices. End-of-season salivary anti-CarLA IgA and IgG were quantified in two grazing seasons (2023–2024) in female kids (<1 year), yearlings (1–2 years), and adults (>2 years), and tested in models of GIN FECs collected four times from June to October each year. Goats in all age groups developed detectable salivary antibodies. Adults exhibited the highest IgA and IgG titres and negative associations between FECs and salivary antibodies in mid-summer (IgG, 2024 p < 0.1) and early fall (IgA, 2023 p < 0.1; IgG, 2024 p < 0.05). Significant (p < 0.05) negative relationships between IgA and FEC were present in fall 2023 and spring 2024 in kids and spring 2024 in yearlings. At the herd level, ITS-2 rDNA nemabiome metabarcoding identified Haemonchus contortus and Trichostrongylus colubriformis as the predominant species across all farms. In 2024 only, farms with higher H. contortus proportions exhibited a negative relationship between anti-CarLA IgA and FEC at FECs < 1009 epg, with IgG trending similarly. Goats on farms using FAMACHA scoring (OR = 0.37, CI 0.16–0.85) or co-pastured with pigs/poultry (OR = 0.07, CI 0.01–0.60) had reduced odds of IgA ≥ 0.501 U/mL. Collectively, these findings demonstrate that Ontario goats develop measurable salivary anti-CarLA antibodies that increase with age. Although negative antibody–FEC associations were identified, relationships varied with isotype, age group, and sampling time point. Future prospective studies are needed to refine optimal timing for anti-CarLA testing in Ontario goats.