Prevalence, fecal egg counts, and species identification of gastrointestinal nematodes in replacement dairy heifers in Canada

摘要

Information is scarce regarding the epidemiology ofgastrointestinal nematodes in Canadian dairy heifers.The objectives of this study were to estimate the prevalenceand fecal egg counts of gastrointestinal nematodesin dairy heifers, and using a novel deep-amplicon sequencingapproach, to identify the predominant gastrointestinalnematode species in Canadian dairy replacementheifers. Fresh environmental fecal samples (n =2,369) were collected from replacement heifers on 306dairy farms across western Canada, Ontario, Québec,and Atlantic Canada. Eggs per gram of feces (EPG)were determined using a modified Wisconsin doublecentrifugationsugar flotation technique. Predominantnematode species at the farm level were identified bydeep-amplicon nemabiome sequencing of the internaltranscribed spacer-2 rDNA locus of nematode thirdstagelarvae. Generalized estimating equations wereused to estimate predicted parasite prevalence andmean EPG in all heifers and by province, allowing forclustering within herds. Individual heifer egg countsranged from 0 to 141 EPG (median: 0 EPG; interquartilerange: 0 to 71 EPG). Gastrointestinal nematodeswere detected in 20.9% (95% confidence interval: 17.2to 24.6%) of heifers, and the predicted mean strongylidEPG accounting for clustering on farms was 1.1 (95%confidence interval: 0.6 to 1.6). The predominant parasitespecies were Cooperia oncophora and Ostertagiaostertagi. This is the first study in Canada to use acombination of deep-amplicon nemabiome sequencingand a traditional egg count method to describe theepidemiology of gastrointestinal nematodes in dairyheifers.