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

Bovine spongiform encephalopathy (BSE) is a progressive fatal neurodegenerative disease of cattle, first recognised in 1986 in the UK. 1 An early study indicated that BSE was consistent with exposure of cattle to a scrapie-like agent via cattle feedstuffs containing ruminant-derived protein. 2 Transmission mainly occurs during calfhood, with the time of infection ranging between 0 and 18 months of age and a typical incubation period of five years. 3 4 In dairy cattle, the age-dependent risk of infection is highest during the first six months of life. 5 Since 1987, 28 countries in Europe, Asia and North America have reported cases of BSE. The International Organisation for Animal Health (OIE) assigns a BSE disease status to member countries, and in 2016 categorised 46 countries as having a negligible BSE risk and 8 as having a controlled BSE risk. 6 In Ireland, the first case of BSE was diagnosed in 1989. 7 By December 31, 2016 , 1660 cases of BSE had been confirmed in Ireland, including four atypical BSE cases, as discussed later. Most clinical BSE cases have been detected in cattle aged between four and eight years, with an age range from three to twelve years. 8 9 Since 1989, it has been a legal requirement for any person observing an animal with clinical signs consistent with BSE to inform the Department of Agriculture, Food and the Marine (DAFM). In line with EU legislation, all cohorts and progeny of BSE-positive animals are traced, killed and disposed of outside the food chain.