Effect of autolysis on the specificity of bovine spongiform encephalopathy rapid tests

Abstract

BackgroundRoutine rapid testing for Bovine Spongiform Encephalopathy (BSE) has highlighted some problems with BSE rapid test performance, the most significant being the number of initially reactive samples and the false positive results on autolyzed tissue. This point is important for BSE active surveillance in risk populations, because tissue autolysis is often unavoidable in routine cases. A robust test suitable for use on field material is therefore needed. To date, very limited information regarding the effect of autolysis on the robustness of rapid tests has been documented; therefore, the National Reference Centre for Animal Encephalopathies (CEA) rapid test laboratory selected 450 autolyzed and negative brain stem samples from fallen stock bovines older than 24 months to assess the specificity of four tests approved for BSE active surveillance: Biorad TeSeE, Enfer TSE version 2.0, Prionics® Check LIA, and IDEXX Herd Check BSE Antigen Kit EIA. The samples were graded according to the degree of autolysis and then dissected into five portions, four of which randomly assigned to processing by rapid tests and one to be available for confirmatory Western blot analysis.FindingsThe specificity of the four systems was 100% for all three grades of autolysis, while the percentage of initially reactive results was 0.00 (95%CI 0.00-0.82), 0.22 (95%CI 0.006-1.23), 0.44 (95%CI 0.05-1.60), and 0.89 (95%CI 0.24-2.26) for the Biorad TeSeE, the Prionics® Check LIA, the IDEXX Herd Check BSE and the Enfer TSE tests, respectively. No association with the degree of autolysis could be drawn.ConclusionsThe present study demonstrates that the four rapid tests can be considered well-running diagnostic tools regardless of tissue quality; nevertheless, the number of initial reactive samples reported for some systems must not be underestimated in routine testing.Furthermore the compliance with the reported performance can be guaranteed only when an ongoing high careful batch quality control system is in place.

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

“…The index herd (the herd of residence of the case animal at time of diagnosis) was visited by DAFM staff to examine the farm, herd movement records and farm records. The field investigation began once a positive screening test result was received, noting the high specificity of these tests 43 . The likely infection window (encompassing the most likely period of infection of the case animal) was determined to be 2010, the year of birth.…”

“…The field investigation began once a positive screening test result was received, noting the high specificity of these tests. 43 The likely infection window (encompassing the most likely period of infection of the case animal) was determined to be 2010, the year of birth. The case animal was born and died in the index herd.…”

Conventional and State-of-the-Art Detection Methods of Bovine Spongiform Encephalopathy (BSE)

“…While correct sampling is important, tissue quality seems to be less important. If sampled tissues are autolyzed, they can still be taken and tested, which is important in any surveillance or diagnostic program [ 99 , 100 ]. In field conditions, brainstem samples are often autolyzed and contaminated with bacteria and other debris (feces, soil, hair).…”

“…Obviously, these factors have an impact on the quality of the sample and affect the performance of the diagnostic test and the results generated [ 88 ]. Meloni et al revealed that four rapid tests (Enfer TSE Kit, Bio-Rad TeSeE test, Prionics ® -Check-LIA test, and IDEXX HerdCheck BSE Antigen Test Kit EIA) can be considered as well-running diagnostics tools regardless of tissue quality [ 100 ]. Wear et al revealed that three rapid tests (Prionics ® -Check Western blot, Platelia, and Enfer) also were able to detect PrP Sc in autolyzed tissues.…”