Proposed criteria to determine whether a territory is free of a given animal disease

Abstract

-This text describes the general principles underlying the concept of disease-free territory and the required statistical basis for the corresponding epidemiological surveillance operations. Among the essential points, it is emphasised that "disease-free" status should be given only under conditions substantiating the absence of infection (or infestation) and not simply on basis of a known low level of infection (or infestation). This manuscript also raises concerns about possible confusion that has arisen between the inevitable requirement to set a threshold on the level of detection of epidemiological surveillance tools, for economic reasons, and the acceptance of a level of infection (or infestation) that is known, but occurring below the accepted threshold, when according the official status of "territory-free from a given disease". In such a situation, it would be preferable to accord the status of "territory where the disease is in the process of eradication". free territory / infectious disease / prevalence rate threshold Résumé -Proposition de critères pour déclarer un territoire indemne d'une maladie animale. Ce texte rappelle les principes généraux sur lesquels devrait être fondée la notion de territoire indemne d'une maladie, ainsi que les bases statistiques nécessaires aux opérations d'épidémiosurveillance correspondantes. Parmi les éléments essentiels, les auteurs insistent sur la nécessité de ne conférer l'appellation « indemne de » que lorsqu'il n'est pas possible de prouver l'infection (ou l'infestation) et non pas lors de la présence certaine d'un faible taux d'infection (ou d'infestation). Ils attirent l'attention sur la confusion qui a dû s'installer entre l'inévitable exigence de fixer une limite au niveau de détec-tabilité des outils d'épidémiosurveillance, pour des raisons économiques, et l'acceptation d'un taux d'infection (ou d'infestation) connu, mais situé au-dessous de ce niveau, pour l'attribution officielle de la qualification « indemne de ». Pour une telle situation (prévalence faible, située au-dessous d'un seuil défini en fonction des caractéristiques épidémiologiques des maladies), l'appellation « territoire où la maladie est en voie d'éradication » est préférable.territoire indemne / maladie infectieuse / prévalence limite acceptable Vet. Res. 32 (2001) 545-563 545

Using Auxiliary Information to Improve Wildlife Disease Surveillance When Infected Animals Are Not Detected: A Bayesian Approach

“…If a management unit (or population) can be declared “disease-free”, these actions can be avoided. Demonstrating “freedom from disease” in an animal population is rooted in regulatory requirements pertaining to national and international domestic animal trade [1], although the phrase can be conceptually and legally ambiguous [2],[3]. The only way to demonstrate an area is truly disease-free is to conduct a complete census, which is almost always impractical.…”

Designing screening protocols for amphibian disease that account for imperfect and variable capture rates of individuals

“…Therefore, it is not possible to formally infer absence, unless the whole population has been tested. Alternatively, managers might choose to declare pathogen-or disease-free populations when the estimated prevalence falls, with a given confidence, under a selected threshold (Dufour et al 2001). Research in veterinary science has dealt extensively with the calculation of optimal sample sizes to estimate such freedom from disease (DiGiacomo and Koepsell 1986, Martin et al 1992, Cameron and Baldock 1998, and the adoption of Bayesian methods has allowed incorporation of prior beliefs about prevalence (Johnson et al 2004).…”

Scientific and technical assistance onEchinococcus multilocularisinfection in animals

“…In addition, the assumption of perfect specificity has an important consequence: if a positive test result is returned by a system having 100% specificity, freedom from infection can no longer be claimed, as all positive results are true. Each surveillance system should be seen to encompass all necessary follow-up testing to resolve potential false positive results (Cannon, 2001;Dufour et al, 2001;Martin et al, 2007).…”