Validation and field evaluation of a competitive inhibition ELISA based on the recombinant protein tSAG1 to detect anti-Neospora caninum antibodies in sheep and goats

• Published in: Veterinary parasitology Vol. 284; p. 109201
• Main Authors: Novoa, María Belén, Aguirre, Nerina Patricia, Ormaechea, Nadia, Palmero, Sebastián, Rouzic, Lisandro, Valentini, Beatriz Susana, Sarli, Macarena, Orcellet, Viviana Mercedes, Marengo, Rafael, Vanzini, Victor René, Primo, María Evangelina
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-08-2020
• Subjects: Animals; Antibodies, Protozoan - blood; Antigens, Protozoan - genetics; Antigens, Protozoan - immunology; ciELISA; Coccidiosis - blood; Coccidiosis - diagnosis; Coccidiosis - veterinary; Diagnosis; Enzyme-Linked Immunosorbent Assay - standards; Enzyme-Linked Immunosorbent Assay - veterinary; Fluorescent Antibody Technique, Indirect - standards; Goat; Goats; N. caninum; Neospora - immunology; Prevalence; Protozoan Proteins - genetics; Protozoan Proteins - immunology; Recombinant Proteins - genetics; Recombinant Proteins - immunology; SAG1; Sensitivity and Specificity; Seroepidemiologic Studies; Sheep; Sheep Diseases - blood; Sheep Diseases - diagnosis; T. gondii; T. gondii; Prevalence; Sheep; Goat; Diagnosis; N. caninum; SAG1; ciELISA
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/j.vetpar.2020.109201

•ciELISAtSAG1 can differentiate N. caninum-infected and uninfected sheep and goats.•ciELISAtSAG1 was highly sensitive and specific to detect anti-N. caninum antibodies.•Cross-reactions were not observed between tSAG1 and anti-Toxoplasma gondii antibodies.•At field evaluation the concordance between ciELISAtSAG1 and IFAT was very good.•The production of tSAG1 recombinant protein is simple and standardized.
Neospora caninum is a protozoan parasite that causes abortion and reproductive failure in small ruminants. We validated and evaluated under field conditions a competitive inhibition ELISA based on the truncated SAG1 protein (tSAG1) from N. caninum for the detection of anti-N. caninum antibodies in sheep and goat flocks. The assay was validated using 80 positive and 142 negative serum samples from sheep and goats analyzed by IFAT and immunoblot (IB). ciELISAtSAG1 was then used to evaluate the prevalence of anti-N. caninum antibodies in 1449 goats from 143 flocks and 385 sheep from 40 flocks and compared to IFAT. The prevalence of anti-Toxoplasma gondii antibodies was evaluated by IFAT. The ciELISAtSAG1 cut-off was ≥ 36 percent inhibition, with a diagnostic sensitivity of 100.0 % (95 % CI = 95.4–100.0 %) and a diagnostic specificity of 98.6 % (95 % CI = 95.0–99.8 %) relative to the agreement between IFAT and IB. The field evaluation revealed a concordance between ciELISAtSAG1 and IFAT of 97.4 %, with an agreement (κ) of 0.90 for sheep sera, and a concordance of 96.5 % with κ = 0.85 for goat sera. The overall prevalence of anti-N. caninum antibodies in sheep was 14.3 % by IFAT and 15.8 % by ciELISAtSAG1. In goats, prevalence was 12.9 % by IFAT and 14.6 % by ciELISAtSAG1. The overall prevalence of anti-T. gondii antibodies was 28.8 % in goats and 43.8 % in sheep. The ciELISAtSAG1 could be useful for large-scale detection of anti-N. caninum antibodies in sheep and goats, and for seroepidemiological investigations due to its appropriate sensitivity and specificity, and the simplicity of production.