Use and comparison of serologic assays to detect anti-Neospora caninum antibodies in farmed red deer (Cervus elaphus)

Abstract

Neospora caninum is a protozoan parasite that cause abortion in different ruminant species, including red deer ( Cervus elaphus). There are no validated assays to be performed with sera from red deer. At the present work, we evaluated the agreement among indirect fluorescent antibody test (IFAT), competitive inhibition ELISA based on a recombinant protein (ciELISA tSAG1) and immunoblot (IB) to detect anti- N. caninum antibodies in a red deer herd that presented reproductive losses due to N. caninum. In addition, we analyzed the relationship between the serologic results and 15 hinds were analyzed by IFAT, ciELISA tSAG1 and IB to detect anti- N. caninum antibodies. In the three assays, the cut-off established for cattle was used. Besides, sera were analyzed by IFAT to detect anti- Toxoplasma gondii antibodies. The hinds were monitored by ultrasound scanning during the gestational period to detect abortions. Gwet’s agreement coefficient (AC1) and the percentage of agreement were used to estimate the agreement between pairs of assays. Chi-square test and odds ratio (OR) were used for the statistical association between abortion and seropositivity to N. caninum or to T. gondii. The N. caninum seropositivity rate was 53.9% (62/115), 57.4% (66/115) and 55.7% (64/115) for IFAT, ciELISA tSAG1 and IB, respectively. The AC1 and percentage of agreement were 0.760% and 87.8% for the pair ciELISA tSAG1 /IFAT, 0.793% and 89.6% for the pair IFAT/IB, and 0.966% and 98.3% for the pair IB/ciELISA tSAG1. The T. gondii seropositivity rate was 53.0% (61/115). Seropositive hinds to N. caninum were more likely to abort than seronegative hinds by the 3 assays. The OR for the association between N. caninum seropositivity and abortion was 72.70, 22.96 and 83.24 when ciELISA tSAG1, IFAT or IB assays were used, respectively. between T. gondii seropositivity and abortion. The three serologic assays were useful to detect N. caninum infected hinds. The validation of the assays for use in red deer would be an improvement for diagnosis of neosporosis in this species.