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

A 2 to 1 matched case control study design was used to analyze herd level r isk factors for Neospora caninum-associated abortion storms in 47 dairy her ds. Data were obtained using a questionnaire regarding the state of affairs at the farms over the 2 years prior to the abortion storm. The questionnai re included 120 variables considered to be potential risk factors for eithe r introduction of infection or recrudescence of chronic infection. The rela tionship between risk factors and case control pairs was analyzed by condit ional logistic regression using a three-steps procedure. In addition, cross sectional serology was used to assess the possible role of concomitant inf ections. The main factors that were significant in the analysis and that were consid ered to have potential biological relevance were the presence of dogs, the presence of poultry, and the feeding of moldy maize-silage during summer. F or both the presence of dogs and the presence of poultry on the farms, a li near 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 rol e of dogs was the significant association between the presence of dogs and the presence of seropositive cattle in the control herds. The feeding of mo ldy fodder is considered to be a factor which may induce recrudescence of a latent N. caninum-infection by mycotctxins causing immune suppression. We also found some evidence for a possible influence of management practices a round calving and a high prevalence of retained afterbirths. No significant association was found for herd level prevalence of antibodies to bovine vi ral diarrhea virus, bovine herpesvirus 1, Leptospira hardjo or Salmonella d ublin. (C) 1999 by Elsevier science Inc.