Syndromic surveillance on phone calls about cattle health problems for early detection of emerging diseases

The aim of this study was to develop a real-time syndromic surveillance system based on calls to the helpdesk ‘Veekijker’ concerning non-specific health problems (drop in milk production, fever, diarrhoea and fertility disorders) in cattle for early detection of emerging infectious diseases. The outbreak with Schmallenbergvirus (SBV) that emerged in the Netherlands in 2011 was used as case study. A time series analysis was run for which data were aggregated on week level. Second, a spatiotemporal cluster analysis was run for which data were aggregated on postal district-week level. In both analyses, at least four consecutive weeks with one or more alerts of increased phone calls on one or more symptoms were considered a signal needing follow-up actions. The results from the time series analysis showed four signals with an increased number of phone calls about at least one of the four symptoms in 2011 and actions would have been taken early August and in September. The spatiotemporal cluster analysis showed ten signals and actions would have been taken mid July until the beginning of September. The syndromic surveillance on phone calls would have resulted in follow-up actions mid July, whereas in reality, without syndromic surveillance, the actions to verify whether a disease had emerged, started on August 25, 2011. This study showed that combining results of real-time syndromic surveillance on ‘Veekijker’ phone calls about cattle health problems provides quantitative information to ’Veekijker’ veterinarians and may increase the sense of urgency in the initial phase of an emerging disease outbreak.