High levels of third-stage larvae (L3) overwinter survival for multiple cattle gastrointestinal nematode species on west
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Parasites & Vectors Open Access
RESEARCH
High levels of third‑stage larvae (L3) overwinter survival for multiple cattle gastrointestinal nematode species on western Canadian pastures as revealed by ITS2 rDNA metabarcoding Tong Wang1,2*, Russell W. Avramenko1, Elizabeth M. Redman1, Janneke Wit1, John S. Gilleard1* and Douglas D. Colwell2*
Abstract Background: The ability of infective larvae of cattle gastrointestinal nematode (GIN) species to overwinter on pastures in northerly climatic zones with very cold dry winters is poorly understood. This is an important knowledge gap with critical implications for parasite risk assessment and control. Methods: Infective third-stage larvae (L3) were quantified in samples of fecal pats, together with adjacent grass and soil, before and after winter on three farms in southern, central and northern Alberta. Nemabiome ITS2 metabarcoding was then performed on the harvested L3 populations to determine the species composition. Finally, parasite-free tracer calves were used to investigate if the L3 surviving the winter could infect calves and develop to adult worms in spring. Results: Farm level monitoring, using solar powered weather stations, revealed that ground temperatures were consistently higher, and less variable, than the air temperatures; minimum winter air and ground temperatures were − 32.5 °C and − 24.7 °C respectively. In spite of the extremely low minimum temperatures reached, L3 were recovered from fecal pats and grass before and after winter with only a 38% and 61% overall reduction over the winter, respectively. Nemabiome ITS2 metabarcoding assay revealed that the proportion of L3 surviving the winter was high for both Cooperia oncophora and Ostertagia ostertagi although survival of the former species was statistically significantly higher than the latter. Nematodirus helvetinaus and Trichostrongylus axei could be detected after winter whereas Haemonchus placei L3 could not overwinter at all. Adult C. oncophora, O. ostertagi and N. helvetianus could be recovered from tracer calves grazing after the winter. Conclusions: The largest proportion of L3 were recovered from fecal pats suggesting this is important refuge for L3 survival. Results also show that L3 of several GIN parasite species can survive relatively efficiently on pastures even in
*Correspondence: [email protected]; [email protected]; [email protected] 1 Department of Comparative Biology and Experimental Medicine, Host‑Parasite Interactions Program, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada 2 Liverstock Parasitology, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images
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