Recombinant NhSAG1 ELISA: a sensitive and specific assay for detecting antibodies against Neospora hughesi in equine serum.

This study introduces a new diagnostic test, the recombinant NhSAG1 ELISA, for detecting antibodies against a parasite called Neospora hughesi in horses, a cause of a neurological disease. The test has shown high sensitivity and specificity, and its high-throughput capability allows screening large sample sets for a better understanding of the prevalence and epidemiology of this parasite.

Research Objective

• This research aimed to provide a new diagnostic method using Recombinant NhSAG1 ELISA for detecting antibodies developed as a response to equine infection by Neospora hughesi, a parasite recently identified as a cause of a neurological disease in horses.

Methodology

• An enzyme-linked immunosorbent assay (ELISA) was developed using the recombinant form of the N.hughesi’s 29-kDa surface antigen (rNhSAG1). This method was devised for diagnosing N.hughesi infections in horses.
• The ELISA results were then compared with Western Blot results for 1006 samples using rNhSAG1 ELISA.
• The study also analyzed reactivity of antibodies in animals previously infected or immunized with N.hughesi, comparing rNhSAG1 with its homologue in another species of the parasite, Neospora caninum (rNcSAG1).

Results

• The rNhSAG1 ELISA exhibited 94.4% sensitivity and 95.0% specificity, showing high accuracy in detecting N.hughesi infections when compared with the more conventional method of N.hughesi Western Blot testing.
• From the 1,917 samples tested by ELISA, there was a seroprevalence of 3.4%, implying that the infection is less common in horses than earlier reported.
• An even lower seroprevalence of 0.9% was reported upon further analysis of the ELISA positive sera through Western blot, revealing only 18 true seropositive samples.

Significance

• The new rNhSAG1 ELISA method, due to its high sensitivity and specificity, has a potential for use in diagnosing N.hughesi infection in horses.
• The test’s high-throughput feature allows for screening large sample sets, which should offer better understanding of the epidemiology and handle prevalence data of N.hughesi infection. It also implies that the infection is less common in horses than previously thought.