Risk factors for Neospora caninum-associated abortion storms in dairy herds in the Netherlands (1995 to 1997)

摘要

A 2 to 1 matched case control study design was used to analyse herd level risk factors for N. caninum-associated abortion storms in 47 dairy herds. Risk factor data were obtained for the 2 years before the abortion storm using a questionnaire covering 120 variables considered to be potential risk factors for either introduction of infection or recrudescence of chronic infection. In addition logistic regression analysis, cross sectional serology was used to assess the possible role of concomitant infections. The main factors considered to have potential biological relevance were: the presence of dogs, the presence of poultry, and the feeding of mouldy maize-silage during summer. For both the presence of dogs and the presence of poultry on the farms, a linear relationship was found between the number of animals and the assessed risk for an abortion storm. These findings suggest a possible role of these species in the transmission of N. caninum. Further evidence for such a role of dogs was the significant association between the presence of dogs and the presence of seropositive cattle in the control herds. The feeding of mouldy fodder is considered to be a factor which may induce recrudescence of a latent N. caninum-infection by mycotoxins causingimmune suppression. Evidence was also found for a possible influence of management practices around calving and a high prevalence of retained afterbirths. No significant association was found for herd level prevalence of antibodies to bovine viral diarrhoea virus, bovine herpesvirus 1, Leptospira hardjo or Salmonella dublin.