Coverage and Representativeness of Passive Surveillance Components for Cattle and Swine in The Netherlands

SIMPLE SUMMARY: To protect animal and human health, it is important to detect disease early and prevent spreading. Other common aims of animal health surveillance are disease monitoring and proving freedom of disease. In a good surveillance system, representative information of farmers and veterinarians from the entire country should be collected. Our study focused on the validity of the Dutch passive surveillance components based on veterinary helpdesk and postmortem data. We examined whether data was received from the entire country and represented the swine and cattle sector in the Netherlands. The difference between the region with the highest and lowest contact rate was 12.8 and 6.1 fold for cattle and pigs, respectively; for postmortem, this was 4.0 and 38.3. Part of the differences could be explained by the distance to the postmortem facility and farm density. We found that veterinary practices serving few farms and veterinary practices serving many cattle farms had fewer contacts compared to other practices. Although this study found regions and practices with lower-than-expected contacts and postmortems, information was obtained from all regions and most veterinarians. The results can be used to improve the coverage and representativeness by an increased focus on specific regions, farms or veterinary practices. ABSTRACT: Common aims of animal health surveillance systems are the timely detection of emerging diseases and health status monitoring. This study aimed to evaluate the coverage and representativeness of passive surveillance components for cattle and swine in the Netherlands from 2015–2019. The passive surveillance components consisted of a telephone helpdesk for veterinary advice and diagnostic and postmortem facilities. Spatial analysis showed heterogeneity (range in RR = 0.26–5.37) of participation across the Netherlands. Generalized linear mixed models showed that distance to the diagnostic facility and farm density were associated with the number of contacts of farmers with the helpdesk and postmortem examination. The contact rate of veterinary practices was associated with their number of clients, ranging in RR from 0.39 to 1.59. We concluded that the evaluation indicated differences in coverage of the passive surveillance components across regions, farms and veterinary practices. Due to the absence of emerging infections in the study period, we were unable to estimate the consequences of the observed differences for the early detection of disease. Nevertheless, regions and veterinary practices with low participation in passive surveillance might be a risk for early detection, and consequently, further understanding of the motivation to participate in passive surveillance components is needed.