A key success factor in the vaccination of dogs against leptospirosis is long term protection against establishment of the renal carrier state, in order to protect other dogs, as well as humans, against this re-emerging zoonotic disease. In this paper, we describe the ability of a new European tetravalent vaccine containing antigen from Leptospira interrogans (sensu lato) serogroups Icterohaemorrhagiae, Canicola, Grippotyphosa and Australis to control infection and renal excretion in dogs at 12 months after vaccination. In order to demonstrate the efficacy of all four vaccine components, four separate challenge studies were performed. For each study two groups of dogs were used (a group receiving the leptospirosis vaccine and a control group). Twelve months after the second vaccination all dogs in the vaccine and control groups were challenged, both intraperitoneally and conjunctivally, using a pathogenic challenge strain from one of four serogroups. Parameters recorded post-challenge were: clinical signs of disease, change in body temperature, total leucocyte count, thrombocyte count, presence of challenge organisms in blood, urine and kidney tissue, and evidence of interstitial nephritis at necropsy four weeks after challenge. The vaccine was able to either prevent or significantly reduce infection following challenge with the strains of all four serogroups. The vaccine was also able to prevent or significantly reduce renal infection following Canicola and Icterohaemorrhagiae challenge, and there was a trend of reduction of renal infection with Australis (serovar Bratislava). In the case of the Grippotyphosa study, challenge led to no detectable renal infection in any dog of the control group. In conclusion, in this study significant protective immunity was achieved in dogs 12 months after a basic vaccination schedule of two doses against strains of serogroups Canicola, Icterohaemorrhagiae, Grippotyphosa and Australis.
