Quantitative investigation of population persistence and recurrent outbreaks of bovine respiratory syncytial virus on dairy farms
De Jong, M.C.; van der Poel, W.H.; Kramps, J.A.; Brand, A.; van Oirschot, J.T.
American Journal of Veterinary Research 57(5): 628-633
1996
ISSN/ISBN: 0002-9645 PMID: 8723872 Document Number: 459410
Objective: To determine if transmission of virus among seropositive cattle is a plausible mechanism for the permanent presence of bovine respiratory syncytial virus (BRSV) in dairy herds, and how likely, with that scenario for persistence, there will be only 1 clinical outbreak of BRSV per year. Design: Build a stochastic model, parameter estimation from serologic data on BRSV, and interpret the estimated parameter values from the model analysis. Sample Population: Monthly data on the prevalence of antibodies directed against BRSV in sera from all cattle in 6 dairy herds. Procedure: Parameter estimation applying general linear models, model analysis using calculation of the reproduction ratio for simplified models, and Monte-Carlo simulation for the whole model. Results: Persistence of BRSV by transmission among seropositive cattle given estimated parameter values would be accompanied by frequent extinctions (once every 1 to 50 years) and long infectious periods in seropositive cattle (100 days). Moreover, in the model, a single clinical outbreak among seronegative cattle only occurred with external forcing. Conclusions: From these data, transmission among seropositive cattle is not a plausible mechanism for persistence of BRSV in dairy herds.