Characterizing state-level patterns of interstate certificates of veterinary inspection exceptions across the United States

Interstate Certificates of Veterinary Inspection (ICVIs) are documents widely used in studies to describe animal movements across the United States (US) and subsequently, explore the potential for disease spread. However, unique state-level exceptions to ICVI documentation exist. This project aimed to describe these exceptions in US state regulations and investigate the association between state-level characteristics - such as in-state cattle shipments and number of slaughter operations - and the number of ICVI exceptions. Exceptions were systematically recorded by accessing official sources. These included exceptions 1) for cattle moving directly to slaughter, 2) for cattle moving to a livestock market, 3) allowing the use of other forms of animal identification, 4) allowing the use of commuter permits, 5) allowing the use of grazing permits, 6) for cattle moving directly to veterinary care, 7) for cattle moving to a feedlot, 8) for cattle moving to an approved tagging site, 9) for cattle moving to their origin farm, 10) for cattle being held in quarantine, and 11) for cattle under a certain age. A multivariable Poisson regression model was used to investigate the association between the number (count) of exceptions and cattle-related characteristics at the state level. Statistical significance was determined at p < 0.05. Results revealed that 86 % of states had at least one exception to ICVI usage, with a mean (±SD) 2.5 (±1.6) exceptions per state. Notably, 82 % of states included exceptions for slaughter movements, and half of the states allowed alternative forms of animal identification. The final model showed that states with 17-33 slaughter operations had a significantly higher rate of exceptions (IRR = 2.12; P = 0.06) compared to those with fewer than 17 slaughtering facilities. Findings from this study showed that basing cattle movement networks solely on ICVI documentation may negatively impact disease traceability in cattle, given that the proportion of states using alternative movement documentation was substantial. Additionally, it highlighted the fact that US states with a high potential impact on disease transmission, such as those having high traffic for cattle slaughter purposes, had a higher number of exceptions to ICVI usages. This indicates critical vulnerabilities in the broader network of cattle movement, highlighting the need for more comprehensive approaches to disease traceability and prevention in the US cattle industry.