Using an epidemiological framework and bovine spongiform encephalopathy investigation questionnaire to investigate suspect bovine spongiform encephalopathy cases: an example from a bovine spongiform encephalopathy case in Ireland in 2015

O’Connor, Jarlath T; Byrne, Justin P; More, Simon J; Blake, Martin; McGrath, Guy; Tratalos, Jamie A; Mcelroy, Maire C; Kiernan, Paul; Canty, Mary J; O’Brien-Lynch, Chris; Griffin, John M

The BSE investigation questionnaire was developed to aid field-based data collection in Ireland. As part of the current study, we have adapted this questionnaire to maximise its usefulness as an investigative tool for suspect BSE cases. Specifically, drawing on current understanding of BSE and on experiences gained with BSE investigations in Ireland, we have developed an epidemiological framework to be used in conjunction with the BSE investigation questionnaire, focusing on (1) confirmation and discrimination; (2) estimating the date and location of exposure; and (3) determining the method/source of exposure (Box). At each step of the framework, we describe the tools available, information required and the relevant questions from the supplementary questionnaire. The steps to be taken during the investigation are guided by the type of BSE (classical or atypical) identified, as determined by OIE-approved discriminatory testing. If atypical H-type or L-type BSE is confirmed, the investigation does not progress beyond '1. Confirmation and discrimination'. If classical BSE is confirmed, the investigation continues to include '2. Estimating the date and location of exposure' and '3. Determining the method/source of exposure'. Decisions with respect to '3. Determining the method/source of exposure' should be made using a legal standard of proof of at least 'on the balance of probabilities' or 'on the preponderance of the evidence', 41 42 after considering all data relevant to the biological plausibility of each alternative. The framework has been developed to be suitable for use during on-farm epidemiological investigations of suspect BSE cases.