A case-control seroepidemiological investigation of Neospora caninum in Ontario dairy herds

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Hobson, Jamie Cameron

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University of Guelph


This thesis evaluated three bovine ELISAs for 'Neospora caninum ' (NC) detection, surveyed the NC seroprevalence, examined the impact of infection on milk production and investigated associations with related abortions in Ontario herds. Five laboratories using three NC ELISAs were found to agree well with an IFAT. Cut-off selection and quality assurance impacted performance. In 88 case-control herds, median seroprevalence was 15.0% and significantly higher in NC-problem herds than non-NC-problem herds (6.1%) or low prevalence herds (4.0%). Milk production in positive cattle from abortion-problem herds was 205kg-276kg/cow/305-days higher than seronegative cattle ('P' = 0.04). Seropositive cattle, and culled seropositive cattle from representative herds produced 151kg/cow/305-days more ('P' = 0.10), and 193kg/cow/305-days more ('P' = 0.04), respectively. Positively associated with NC-related abortions were: herd seroprevalence, exposure to dogs, dogs defecating in feed mangers, and the rates of retained fetal membranes and cows returning to estrus after pregnancy determination. Negatively associated were: observations of stray cats and wild canids, and housing heifers on loafing packs.



bovine ELISAs, Neospora caninum, detection, seroprevalence, infection, milk production, abortion, dairy herds