Use of a preclinical test in the control of classical scrapie

• Published in: Journal of general virology Vol. 91; no. Pt 10; pp. 2642 - 2650
• Main Authors: BODEN, L. A, HOUSTON, F, FRYER, H. R, KAO, R. R
• Format: Journal Article
• Language: English
• Published: Reading Society for General Microbiology 01.10.2010
• Subjects: Animals; Biological and medical sciences; Disease Transmission, Infectious - prevention & control; Fundamental and applied biological sciences. Psychology; Mass Screening - methods; Microbiology; Miscellaneous; Models, Statistical; Non conventional transmissible agents; Other Agents; Scrapie - diagnosis; Scrapie - epidemiology; Scrapie - prevention & control; Sheep; United Kingdom - epidemiology; Virology; Prion disease; Nervous system diseases; Scrapie; Cerebral disorder; Infection; Vertebrata; Mammalia; Central nervous system disease; Sheep; Degenerative disease; Prion; Artiodactyla; Spongiform encephalopathy; Veterinary; Ungulata
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/vir.0.022566-0

Scrapie control in Great Britain (GB) was originally based on the National Scrapie Plan's Ram Genotyping scheme aimed at reducing the susceptibility of the national flock. The current official strategy to control scrapie in the national flock involves culling susceptible genotypes in individual, known affected flocks (compulsory scrapie flock scheme or CSFS). However, the recent development of preclinical test candidates means that a strategy based on disease detection may now be feasible. Here, a deterministic within-flock model was used to demonstrate that only large flocks with many home-bred ewes are likely to be a significant risk for flock-to-flock transmission of scrapie. For most other flocks, it was found that the CSFS could be replaced by a strategy using a currently available live test without excessive risk to other farmers, even if the proportion of susceptible genotypes in the flock is unusually large. Even for flocks that represent a high risk of harbouring a high prevalence of infection, there would be limited probability of onward transmission if scrapie is detected soon after disease introduction (typically less than 5 years). However, if detection of disease is delayed, the existing CSFS strategy may be the most appropriate control measure in these cases.