One-Year Duration of Immunity in Dogs for Leptospira Interrogans Serovar Icterohaemorrhagiae After Vaccination

Little information is available regarding the duration of immunity achieved by Leptospira vaccination. The aim of this study was to assess in dogs the one-year protection induced by a leptospirosis vaccine against a Leptospira (L.) interrogans serovar icterohaemorrhagiae challenge. Six 8-9 week old dogs were immunised twice at a 3-week interval with a bivalent vaccine composed of inactivated bacterins of L. interrogans serovar canicola and L. interrogans serovar icterohaemorrhagiae (CANIGEN® L, VIRBAC, France) and served as the vaccinated group. Six age-matched dogs were used as the control group. All dogs were challenged with L. interrogans serovar icterohaemorrhagiae 52 weeks after the primary vaccination. The control dogs developed mild clinical signs, leukocytosis, leptospiremia and became renal carriers as demonstrated by positive results in urine culture and interstitial nephritis. In the vaccinated group, only one dog developed leptospiremia and shed leptospires in the urine. These results clearly demonstrated a significant one year protection by CANIGEN® L against leptospiremia, renal carrier state and urinary shedding after experimental infection with L. interrogans serovar icterohaemorrhagiae.