Evaluation of the diagnostic potential and DIVA capability of recombinant LigBCon1-5 protein of Leptospira interrogans serovar Pomona in canine leptospirosis

Background: Canine leptospirosis is a serious public health concern. Aims: This study aims to investigate the feasibility of first to fifth domains of LigB antigen (rLigBCon1-5) as a serodiagnostic marker for detecting canine leptospirosis. Methods: A total of 340 unvaccinated canine serum samples were screened using Microscopic Agglutination Test (MAT) and rLigBCon1-5 based IgG Indirect-ELISA (I-ELISA). Further, 60 vaccinated canine sera were screened using MAT and rLigBCon1-5 based Latex Agglutination Test (LAT). Results: MAT results revealed seropositivity of 28.6%. The relative sensitivity, specificity and accuracy of IgG I-ELISA in comparison to MAT were 100%, 96.0% and 97.2% respectively. Out of 60 vaccinated sera, 46 sera reacted with MAT alone while eight sera reacted by both the tests while six sera were non-reactive by both the tests. Anti-LigB antibodies were detected in eight canine sera by rLigBCon1-5 based LAT. In five LAT reactive sera, agglutinins of locally circulating serovars Grippotyphosa (n=4) and Australis (n=1) were detected. In three LAT reactive sera, agglutinins against Icterohaemorrhagiae (n=3) produced due to natural infection were present. Conclusions: IgG I-ELISA can be employed as an alternative test instead of MAT The rLigBCon1-5 based LAT detected anti-LigB antibodies in eight vaccinated sera where partial and total vaccine failure occurred due to limited efficacy spectrum of Nobivac® RL which could not provide cross-protection against locally circulating serovars which were not included in the vaccine and due to cold chain breakage. The rLigBCon1-5 antigen based LAT possesses DIVA capability when employed as a pen-side test for detecting canine leptospirosis.