Elapsed time to detect classical swine fever – predicted by simulation

Saara Raulo and Tapani Lyytikäinen


In addition to the endemic occurrence of classical swine fever (CSF) in wild boar, in the EU-countries, several countries have experienced an outbreak of CSF preceded by a period of offi cial freedom of disease. Such epidemics have occurred in Belgium in 1993–94, in the Netherlands in 1997–98, and in the UK in 2000. Characteristics for those epidemics were the manifestation of mild and vague clinical signs CSF on the infected farms. In these cases, detection of the index outbreak took place only after several weeks. The length of the time until fi rst detection has a major infl uence on the final size and duration an epidemic, and thus affects fi nal consequences. In order to investigate structures most likely leading detection, factors affecting, and length of predicted fi rst detection time of CSF in Finland, a simulation modeling approach was applied. Prevailing conditions in Finland, and an outbreak with clinical manifestation resembling that in Europe, were taken in account. The model simulates events starting from fi observation of disease on the farm, until positive CSF analyses. Detection of the index outbreak will most probably take place nine weeks after the fi rst farm has been infected in Finland. Fifty percent of the observations fi t between 48 and 86 days. Initiative action towards CSF diagnosis will take place on the farm. Expected detection time of the index farm in Finland, as revealed by the model, corresponds to experienced non-wild boar related epidemics in Europe. Direct suspicion based on clinical signs is not likely. On the contrary, it is likely that the veterinarian will pay several visits on the farm, and successive samples will be sent for analysis before fi nal CSF diagnosis. On the other hand, once CSF analysis concluded, analysis will most likely reveal positive of CSF. By accelerating decisions on the farm and at the investigating laboratory, it is possible to cut the time passing before detecting the index farm in Finland.