Evaluation of Serological Methods and a New Real-Time Nested PCR for Small Ruminant Lentiviruses
Jessica Schaer,
Zeljko Cvetnic,
Tomislav Sukalic,
Sven Dörig,
Martin Grisiger,
Carmen Iscaro,
Francesco Feliziani,
Folke Pfeifer,
Francesco Origgi,
Reto Giacomo Zanoni,
Carlos Eduardo Abril
Affiliations
Jessica Schaer
Institute of Virology and Immunology IVI, in Cooperation with the Vetsuisse-Faculty of the University of Bern, 3012 Bern, Switzerland
Zeljko Cvetnic
Regional Veterinary Department Križevci, Croatian Veterinary Institute, Zakmandijeva 10, 48260 Križevci, Croatia
Tomislav Sukalic
Regional Veterinary Department Križevci, Croatian Veterinary Institute, Zakmandijeva 10, 48260 Križevci, Croatia
Sven Dörig
Beratungs-und Gesundheitsdienst für Kleinwiederkäuer (BGK/SSPR), 3362 Niederoenz, Switzerland
Martin Grisiger
Veterinaerdienst der Urkantone, 6440 Brunnen, Switzerland
Carmen Iscaro
National Reference Laboratory for Ruminant Retroviruses, Istituto Zooprofilattico, Sperimentale dell’Umbria e delle Marche Togo Rosati, 06126 Perugia, Italy
Francesco Feliziani
National Reference Laboratory for Ruminant Retroviruses, Istituto Zooprofilattico, Sperimentale dell’Umbria e delle Marche Togo Rosati, 06126 Perugia, Italy
Small ruminant lentiviruses (SRLVs), i.e., CAEV and MVV, cause insidious infections with life-long persistence and a slowly progressive disease, impairing both animal welfare and productivity in affected herds. The complex diagnosis of SRLVs currently combines serological methods including whole-virus and peptide-based ELISAs and Immunoblot. To improve the current diagnostic protocol, we analyzed 290 sera of animals originating from different European countries in parallel with three commercial screening ELISAs, Immunoblot as a confirmatory assay and five SU5 peptide ELISAs for genotype differentiation. A newly developed nested real-time PCR was carried out for the detection and genotype differentiation of the virus. Using a heat-map display of the combined results, the drawbacks of the current techniques were graphically visualized and quantified. The immunoblot and the SU5-ELISAs exhibited either unsatisfactory sensitivity or insufficient reliability in the differentiation of the causative viral genotype, respectively. The new truth standard was the concordance of the results of two out of three screening ELISAs and the PCR results for serologically false negative samples along with genotype differentiation. Whole-virus antigen-based ELISA showed the highest sensitivity (92.2%) and specificity (98.9%) among the screening tests, whereas PCR exhibited a sensitivity of 75%.
