Forty-four specific pathogen-free beagles, median age 65 days, received two subcutaneous doses of either a commercially available, five-way combination vaccine or the same vaccine in combination with a tetravalent Leptospira bacterin (Canicola, Grippotyphosa, Icterohaemorrhagiae, Pomona). They were subsequently challenged with a pathogenic strain L kirschneri serovar Grippotyphosa 470 days following completion of the vaccination protocol. Titres of agglutinating serum antibodies were determined at various time points before and after both vaccination and challenge, along with postchallenge reisolation of the challenge organisms from blood and urine, and evaluation of renal histopathology. Clinical signs of generalised leptospirosis were not observed in any of the dogs after challenge. In order to demonstrate efficacy, leptospirosis was defined as having at least one positive urine sample and a positive renal histopathology score; or, in the absence of renal pathology, multiple positive urine samples. Leptospiremia was not demonstrated in any of the vaccinated dogs versus 27 per cent of the controls; leptospiruria was noted in 5 per cent of the vaccinates compared with 76 per cent of controls; and renal lesions were observed in 15 per cent of the vaccinates and 65 per cent controls. Using these criteria, the vaccine was able to significantly prevent leptospirosis (P=0.0001) in the vaccinated animals. This study establishes duration of immunity of at least 15 months for the prevention of disease and renal excretion of leptospires for the Leptospira serovar Grippotyphosa fraction of a quadrivalent Leptospira vaccine.
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Funding This study was supported by Merial.
Competing interests The study was originally run by Merial, now a part of Boehringer Ingelheim Animal Health. DAG is an employee of BI Animal Health.
Ethics approval This study was approved and conducted in accordance with an Animal Procedure Statement approved by the Merial Institutional Animal Care and Use Committee (IACUC) and all applicable federal and local animal welfare regulations.
Provenance and peer review Not commissioned; externally peer reviewed.
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