Global perspective on bovine abortion - current prevalences, normal rates, diagnoses and aetiologies: a mini-review

The case definition of bovine abortion varies with the purpose of use from legislative and research to field definitions; it generally encompasses days 42–260 of gestation. This variation can affect comparisons between prevalence rates. Animal-level prevalence estimates vary between 5 and 20% (mean ~10%) while herd-levels vary between 0 and 30% in published studies. Intervention thresholds (‘normal herd-level abortion rate’) also vary widely from 1 to 10% depending on the case definition and the underlying region-specific abortion rate. The infectious abortion diagnosis rate globally is ~45% with Neospora caninum being the most commonly detected abortifacient. Thus, the majority of abortions, in particular, sporadic (not outbreak) cases, have no diagnosed cause. However, current advances in the routine application of molecular diagnostics both for pathogens and for lethal alleles is steadily reducing this diagnosis-not-reached rate.