Development Of Experimental Inactivated Vaccine For Bovine Leptospirosis

DEVELOPMENT OF EXPERIMENTAL INACTIVATED VACCINE FOR BOVINE LEPTOSPIROSIS Name : G. BALAKRISHNAN. Degree for which submitted : Ph.D. in Veterinary Microbiology Chairman : Dr. PARIMAL ROY, Professor and Head, Central University Laboratory, Centre for Animal Health Studies, Chennai – 51 Year and University : 2009 Tamilnadu Veterinary and Animal Sciences University, Chennai-600 051. Sero survey against leptospirosis by MAT was conducted on 3605 serum samples collected from cattle and buffaloes suffering from abortion, repeat breeding, jaundice haemorrhagic mastitis and apparently healthy animals from 16 different districts of Tamil Nadu, 12 different districts of Andhra Pradesh and a private farm in Gujarat state. Seropositivity was found to be 40.39 per cent, 50.21 per cent and 34.74 per cent among cattle and 75.66 per cent, 68.64 per cent and 54.14 per cent among buffaloes in Tamil Nadu, Andhra Pradesh and Gujarat respectively. Seropositivity was more in exotic pure breeds (50.00 per cent), followed by indigenous pure breeds (34.38 per cent) and cross breeds (32.74 per cent) cattle. Meanwhile among buffaloes, seropositivity was more in Murrah (58.25 per cent), followed by Pandharpuri (40.91 per cent) and Jaffrabadi (37.50 per cent) respectively. Males were more positive than females. A total of 555 sera samples from different animal conditions which were MAT positive were found for have elevated levels of bilirubin, SGOT and SGPT. Only 115 sera samples from different clinical condition like abortion repeat breeding, jaundice and haemorrhagic mastitis and apparently healthy animals were screened for the presence of Leptospira specific antibody and antigen. Sixty four (55.65 per cent) samples were positive for antibody by MAT whereas 26.09 per cent samples were positive for Leptospira by DFM and 20.87 per cent samples were positive for pathogenic leptospiral DNA by PCR test. Out of 30 sera samples screening for isolation, 9 isolates of australis (5), hebdomadis (3) and ballum (1) were obtained. In sequence analysis no significant variation could be observed with reference strains. Since the serovars australis, ballum, hardjo, hebdomadis and pomona were consistently prevalent, they were selected as seed bacteria for the preparation of Leptospira experimental vaccines. Formalin inactivated two different kinds of adjuvanted pentavalent vaccines were prepared. Vaccine I was adjuvanted with Montanide ISA 206 and vaccine II was adjuvanted with Aluminium hydroxide gel. Both the experimental vaccines were found to be potent and safe. Duration of the immunity for both the vaccines was studied in rabbits under experimental condition and in cattle under field condition. High antibody titre of 6.84 log2 to 9.64 log2 with vaccine I (Montanide adjuvanted) and 5.64 to 7.44 log2 with vaccine II (Aluminium hydroxide adjuvanted) were found at 180 days in rabbits. For cattle, GM – MAT titres of 6.84 log2 to 7.69 log2 were observed against vaccine – I at 150 days and such titres were seen with vaccine – II at 120 days. Thus vaccine I was found to be a better vaccine than vaccine II. However both the vaccines showed high immune response of 5.64 log2 at 6 months of immunization.