Cattle movement as a risk factor for epidemics.

Abstract

Cattle movement is one of the most important risk factors for the occurrence of an epidemic. It is a legal requirement in Switzerland that every cattle movement be reported, and this information is held in the Swiss cattle movement database (Tierverkehrsdatenbank, TVD). Using this data we examined all movements, focusing on the geographical distribution of these movements in relation to the spread of epizootic diseases. We considered the period 01 January 2011 through 30 January 2012, in which a total of 786'462 cattle were moved. Looking at premises individually, a maximum of 901 possible transfers of an infectious agent were found on a specific day after the arrival of another cattle. Furthermore, we found that there were more cattle movements in summer than in winter, due to movements of cattle to and from alpine pastures. There were also prominent regional differences. On the first day after the arrival of a cattle there was a minimum of zero and a maximum of 99'168 possible transfers of an infectious agent. Nevertheless, in most cases there were no cattle moved on the first day following the arrival of a cattle (91.4%). In terms of our epizootics of interest, the following numbers of cattle were moved within the relevant incubation periods: 19'779'551 possible transfers for the Lumpy skin disease, with an incubation period of 28 days; 9'891'665 or 15'025'741 possible transfers for foot and mouth disease, depending on the incubation period of 14 or 21 days; 15'025'741 possible transfers for cattle plague and vesicular stomatitis, both with an incubation period of 21 days. The presented data show a large cattle traffic in Switzerland, and therefore suggest that it is very seldom that an infectious agent is able to start an epidemic.