Causes of delayed outbreak responses and their impacts on epidemic spread

Abstract

Livestock diseases have devastating consequences economically, socially and politically across the globe. In certain systems, pathogens remain viable after host death, which enables residual transmissions from infected carcasses. Rapid culling and carcass disposal are well-established strategies for stamping out an outbreak and limiting its impact; however, wait-times for these procedures, i.e. response delays, are typically farm-specific and time-varying due to logistical constraints. Failing to incorporate variable response delays in epidemiological models may understate outbreak projections and mislead management decisions. We revisited the 2001 foot-and-mouth epidemic in the United Kingdom and sought to understand how misrepresented response delays can influence model predictions. Survival analysis identified farm size and control demand as key factors that impeded timely culling and disposal activities on individual farms. Using these factors in the context of an existing policy to predict local variation in response times significantly affected predictions at the national scale. Models that assumed fixed, timely responses grossly underestimated epidemic severity and its long-term consequences. As a result, this study demonstrates how general inclusion of response dynamics and recognition of partial controllability of interventions can help inform management priorities during epidemics of livestock diseases.

Inferring transmission routes for foot-and-mouth disease virus within a cattle herd using approximate Bayesian computation

“…Nevertheless, this is a simplification of real infection to detection and detection to slaughter times. In 20 reality there will be heterogeneity between individual farms and some may experience longer delays, changing the shape of the outbreak [46]. Therefore it is useful to consider different scenarios to show the range of results.…”

“…Upon detection, some measures can be applied immediately, such as isolation, whereas the slaughter of animals will occur after a delay. The time from detection to slaughter can vary greatly between farms but was estimated to be on average close to one day in the later stages of the 2001 UK epidemic when response times were quickest [46, 52].…”

Coupling spatial statistics with social network analysis to estimate distinct risk areas of disease circulation to improve risk‐based surveillance

“…Therefore, the use of animal movements alone (e.g., ranking farms based on the number of animals transported to and into farms (Ezanno et al, 2020;Firestone et al, 2012)) to identify farms at greater risk of becoming infected or infecting others does not account for the risk of reintroducing infection in areas with greater potential of local transmission risk (Björnham et al, 2020;Cárdenas et al, 2019;Tao et al, 2021).…”

“…Nevertheless, in Brazil, for most endemic and even reportable diseases, such as EIAV, animals are allowed to be transported among areas regardless of known or unknown disease occurrence and anticipated risk of disease dissemination (Barzoni et al., 2018; Fèvre et al., 2006). Therefore, the use of animal movements alone (e.g., ranking farms based on the number of animals transported to and into farms (Ezanno et al., 2020; Firestone et al., 2012)) to identify farms at greater risk of becoming infected or infecting others does not account for the risk of reintroducing infection in areas with greater potential of local transmission risk (Björnham et al., 2020; Cárdenas et al., 2019; Tao et al., 2021).…”

Implications of partial culling on African swine fever control effectiveness in Vietnam

“…The current study did not investigate further, how extended time spans could be explained, but other factors than the mode of culling are known to influence this parameter substantially (21). As the competent authority in charge of culling is the local veterinary office in conjunction with differing other local authorities, the preparedness and also the availability of human and financial resources to implement measures will have varied throughout the study.…”