Moving-Average Trigger for Early Detection of Rapidly Increasing Mortality in Caged Table-Egg Layers

Abstract

Rapidly increasing and unexplained mortality in commercial poultry flocks may signal the presence of a highly transmissible and reportable disease. Activation of an infectious-disease surveillance system occurs when a key production parameter, i.e., mortality, changes. Various triggers have been proposed to alert producers when mortality exceeds normal limits for a given production system to enable early detection of such diseases. In this article we demonstrate that a simple moving-average trigger is useful for detecting any disease syndrome in caged table-egg layer flocks that manifests itself as sudden, rapidly increasing mortality. We superimposed HPAI disease mortality output data derived from a disease transmission model and from a naturally occurring HPAI outbreak onto normal mortality data from 12 healthy commercial egg-layer flocks, and compared the performance of 7-day moving-average triggers to previously proposed triggers. The moving-average trigger is more efficient, resulting in fewer false-positive alerts and an earlier time to disease detection. It can be easily calculated by using a computer spreadsheet providing only 7 days of mortality data and can be practically and inexpensively implemented by large commercial poultry integrators. A moving-average trigger can be an active component of a production-based surveillance system.

Risk Reduction Modeling of High Pathogenicity Avian Influenza Virus Titers in Nonpasteurized Liquid Egg Obtained from Infected but Undetected Chicken Flocks

“…After the declaration of an animal health emergency and establishment of a containment area, which initially may encompass large jurisdictional areas such as an entire U.S. state, the threshold for reporting by growers is expected to be much lower. Three‐times a seven‐day moving average has been shown to result in earlier reporting by producers and more closely represents a trigger for enhanced passive surveillance reporting of HPAI disease in caged table‐egg layers . This type of surveillance may become important in situations where laboratory capacity or other logistical factors delay the implementation of daily RRT‐PCR testing.…”

“…Multiples of a moving average were used as a trigger to simulate HPAI disease detection by a grower during a heightened awareness period following the establishment of the HPAI disease containment zone. In this option, a moving‐average trigger from the USDA, HPAI Secure Egg Supply Plan (SES Plan), in combination with an absolute‐mortality trigger was used .…”

“…For the purpose of calculating a weekly moving average, normal mortality for seven days before the disease introduction (i.e., ) had to be calculated. Note that was simulated by randomly selecting a contiguous set of mortality numbers from normal mortality data for table‐egg‐layer flocks provided by the U.S. egg industry . This approach was taken as the sequence of normal mortality values in commercial table‐egg‐layer flocks is typically autocorrelated and, hence, standard simulation approaches treating them as independent identical random variables may be inaccurate.…”

Systematic review of surveillance systems and methods for early detection of exotic, new and re-emerging diseases in animal populations

“…This category considered mathematical models that were used to explore epidemiological and disease data related to surveillance and/or to evaluate distinct health measures (n = 20) [27,32,49,50,53,61,72,79,96,101,103,[109][110][111][112][113][114][115][116][117]. We found a wide range of models, such as linear, logistic, binomial, Poisson, time series, or CART.…”

Using quantitative disease dynamics as a tool for guiding response to avian influenza in poultry in the United States of America

“…For an example of the former, a within-flock model was used to generate plausible outbreak data against which the efficacy of various outbreak detection methods were compared (Malladi et al, 2011). For an example of the latter, a within-flock model showed that vaccines conferring incomplete protection could counterintuitively increase the infectiousness of a flock, by delaying the time to detection and depopulation (Savill et al, 2006).…”