The National Veterinary Laboratory, Bülowsvej 27, DK-1790, Copenhagen V, Denmark
The survivorship of animals persistently infected with bovine virus diarrhoea virus was studied in ten Danish dairy herds. The ages of 34 persistently infected animals were compared with the ages of non-persistently infected animals in the herds in a cross-sectional study in which the risk rate of removal of animals in the two groups within 1 year was estimated from an exponential probability function of the age. In a cohort study, the 34 persistently infected animals were followed from the date of the initial blood test and onwards and the risk rates of dying or being slaughtered due to unthriftiness or either of these events were calculated.
The attributable risk of leaving the herds within 1 year was 0.35 among persistently infected animals. The risk rate of dying or being slaughtered due to unthriftiness within 1 year was 0.28 and 0.31, respectively; the risk rate of either of these events was 0.5.
This article was published in Preventive Veterinary Medicine, 15, H. Houe, Survivorship of animals persistently infected with bovine virus diarrhoea virus (BVDV), 275-283, Copyright Elsevier 1993.