Evaluation of the Dutch passive surveillance system for animal health: Past, present and future perspectives

Abstract

Infectious animal diseases such as Foot-and-Mouth Disease, Bluetongue, Avian Influenza, and emerging zoonoses pose a major threat to animal and public health, food security, and trade. Effective disease surveillance is critical to early detect disease outbreaks, minimize health risks, and economic impact. Surveillance combines systematic data collection, analysis, and reporting, with passive surveillance playing an important role in the Netherlands. Farmers and veterinarians are legally required to report notifiable diseases, while voluntary reporting through the veterinary helpdesk and postmortem examinations at Royal GD provides additional signals. This dissertation provides the first scientific evaluation of the Dutch passive surveillance system. Four key objectives were addressed: assessing representativeness of collected data, evaluating its contribution to disease detection, determining its ability to detect changes in animal health status, and identifying motivations and barriers for participation. Findings showed that data coverage generally matched farm, however certain regions showed over- or underrepresentation. Passive surveillance proved vital in detecting Highly Pathogenic Avian Influenza in poultry, while also showing potential in identifying emerging or poorly defined diseases through patterns of excess mortality in cattle. Farmers and veterinarians demonstrated willingness to engage, with trust and farmer-veterinarian relationship as important factors. The study concludes that Dutch surveillance is effective but can be strengthened. Improvements include clearer definitions of excess mortality, better understanding of sector differences, and maintaining trust through transparent communication. Future developments, including syndromic surveillance and Precision Livestock Farming, can further enhance early detection and safeguard both animal and public health.