A multipronged approach for the detection of leptospirosis in captive sloth bears (<i>Melursus ursinus</i>) in Agra and Bannerghatta sloth bear rescue centers in India

Abstract

Leptospirosis is an exacerbating factor responsible for the drastic decline of sloth bear population in India. In this study, a multipronged approach based on antigen detection using Polymerase Chain Reaction (PCR) employing G1/G2 and LigBF/LigBR primers, antibody detection using Microscopic Agglutination Test (MAT) and recombinant LigBCon1-5 antigen based Latex Agglutination Test (rLigBCon1-5 LAT), serum biochemistry using hepatic (serum glutamate oxalo acetic transaminase (SGOT) and serum glutamate pyruvic transaminase (SGPT) and renal biomarkers (blood urea nitrogen (BUN) and Creatinine) and gross/histopathological evidence in liver and kidneys were employed to investigate leptospirosis in captive sloth bears. A total of 133 serum samples collected from Agra (n=113) and Bannerghatta (n=20) sloth bear rescue centers were screened using MAT and rLigBCon1-5 LAT. A total of 87 and 78 sera tested positive by MAT and LAT respectively. Pyrogenes was the leading serovar obtained using MAT followed by Icterohaemorrhagiae, Javanica, Grippotyphosa, Canicola and Tarassovi. The relative sensitivity, specificity and accuracy of rLigBCon1-5 LAT in comparison to MAT were 89.66%, 100% and 93.23% respectively. PCR performed on hepatic and renal tissues showed amplicon of 285 and 219 base pairs for G1/G2 and LigBF/LigBR primers respectively. Gross evidence (icteric liver, severely engorged hepatic sinusoids, congested kidneys with necrotic white spots on sub capsular surface), histopathology (severe hepatic degeneration and tubulointerstitial nephritis) and elevated hepatic/renal biomarkers were suggestive of leptospirosis. This study suggests that rLigBCon1-5 LAT can be employed as a pen-side test for detecting leptospirosis in sloth bears.