Key result
Serial testing with commercial ELISAs achieves 100% diagnostic specificity for foot-and-mouth disease.
Why the study?
What are the diagnostic specificities of two commercial screening ELISAs for foot-and-mouth disease in cattle, sheep, and pigs in New Zealand?
Cross-Sectional (n=2,433)
What are the diagnostic specificities of two commercial screening ELISAs for foot-and-mouth disease in cattle, sheep, and pigs in New Zealand?
The diagnostic specificities of two commercial ELISAs for foot-and-mouth disease in New Zealand livestock are high (>99.5%), and using them in series could improve overall specificity for surveillance.
Supports serial ELISA testing for FMD surveillance in New Zealand livestock; extends specificity data but leaves open prospective validation.
AIMS: To determine the diagnostic specificities of two commercial screening ELISA, the Bommeli/IDEXX Chekit FMD 3ABC indirect ELISA (ELISA-1) and the Ceditest FMDV NS blocking ELISA (ELISA-2), for foot-and-mouth disease (FMD) in cattle, sheep and pigs in New Zealand, and to compare them with other published studies. To consider the implications for FMD surveillance of using two ELISA in series, a consideration arising from the absence of a gold standard virus neutralisation test (VNT) in New Zealand. METHODS: Serum samples from non-infected cattle (n=1,015), sheep (n=1,185), and pigs (n=233) from New Zealand were tested in ELISA-1 and ELISA-2 for the detection of serum antibodies against non-structural proteins of the FMD virus. The ELISA were performed according to the manufacturers' instructions. RESULTS: The diagnostic specificities for ELISA-1 for cattle, sheep and pigs were 99.9%, 99.7% and 99.6%, respectively, and for ELISA-2 were 99.5%, 99.7% and 99.6%, respectively. False-positive reactors in one ELISA were negative in the other ELISA, and vice versa. Using the diagnostic sensitivity data taken from international studies and the diagnostic specificities calculated in this study resulted in overall specificities of 100% in cattle and sheep using serial test interpretation, and 99.2% and 99.0%, respectively, using parallel test interpretation. Diagnostic sensitivities available in the literature varied considerably, and the associated overall serial sensitivity could be as low as 78.7% in cattle and 33.2% in sheep. CONCLUSIONS: Diagnostic specificities for both ELISA for the target population were comparable with those obtained in livestock populations elsewhere. In surveillance to re-establish New Zealand's freedom from FMD, the use of two ELISA in series would improve the overall specificity in individual animals. However, care would be required to ensure that herd sensitivity was sufficient to detect infection.
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Kittelberger et al. (2008) conducted a cross-sectional in Foot-and-mouth disease (n=2,433). Bommeli/IDEXX Chekit FMD 3ABC indirect ELISA and Ceditest FMDV NS blocking ELISA was evaluated on Diagnostic specificity. Two commercial ELISAs demonstrated high diagnostic specificities (≥99.5%) for foot-and-mouth disease in non-infected cattle, sheep, and pigs, reaching 100% when used in series.
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