Abstract:
Diagnostic performance of an indirect enzyme-linked immunosorbent assay (I-ELISA)
based on a recombinant nucleocapsid protein (rNP) of the Rift Valley fever virus (RVFV) was validated
for the detection of the IgG antibody in sheep (n = 3367), goat (n = 2632), and cattle (n = 3819) sera.
Validation data sets were dichotomized according to the results of a virus neutralization test in sera
obtained from RVF-endemic (Burkina Faso, Democratic Republic of Congo, Mozambique, Senegal,
Uganda, and Yemen) and RVF-free countries (France, Poland, and the USA). Cut-off values were
defined using the two-graph receiver operating characteristic analysis. Estimates of the diagnostic
specificity of the RVFV rNP I-ELISA in animals from RVF-endemic countries ranged from 98.6%
(cattle) to 99.5% (sheep) while in those originating from RVF-free countries, they ranged from 97.7%
(sheep) to 98.1% (goats). Estimates of the diagnostic sensitivity in ruminants from RVF-endemic countries ranged from 90.7% (cattle) to 100% (goats). The results of this large-scale international
validation study demonstrate the high diagnostic accuracy of the RVFV rNP I-ELISA. Standard
incubation and inactivation procedures evaluated did not have an adverse effect on the detectable
levels of the anti-RVFV IgG in ruminant sera and thus, together with recombinant antigen-based
I-ELISA, provide a simple, safe, and robust diagnostic platform that can be automated and carried
out outside expensive bio-containment facilities. These advantages are particularly important for
less-resourced countries where there is a need to accelerate and improve RVF surveillance and
research on epidemiology as well as to advance disease control measures.
