Application of survival analysis to identify management factors related tothe rate of BHV1 seroconversions in a retrospective study of Dutch dairy farms
G. Van Schaik et al., Application of survival analysis to identify management factors related tothe rate of BHV1 seroconversions in a retrospective study of Dutch dairy farms, LIVEST PROD, 60(2-3), 1999, pp. 371-382
The prevalence of Bovine herpes virus type 1 (BHV1) at dairy farms is depen
dent on several factors, First, the prevalence is influenced by introductio
n of BHV1 at the farms, which is dependent on the risk factors for introduc
tion. Second, the BHV1 prevalence might also be influenced by reactivation
of BHV1 within the farm, which might be affected by the management of the f
arm. In this study the relations between risk factors, management factors a
nd the estimated time since latest BHV1 outbreak were investigated by means
of Cox regression analysis. The results showed that direct animal contacts
(i.e. purchase of cattle and returning export cattle) and occasional visit
ors-increased the rate of BHV1 outbreaks on dairy farms. Management factors
related to reactivation of BHV1 at dairy farms were all related to a loose
housing system which incurred an increased risk of reactivation of BHV1 at
the farm. The reactivation was facilitated when the barn was overcrowded (
i.e, more cows than cubicles in the barn). To minimise the risk of introduc
tion of BHV1 at a farm the farmer should banish direct animal contacts and
limit the number of contacts with visitors. Stress and an overcrowded barn
should be avoided.