Efficacy of a multivalent DAPPi-Lmulti canine vaccine against mortality, clinical signs, infection, bacterial excretion, renal carriage and renal lesions caused by Leptospira experimental challenges

Efficacy of the Leptospira components of EURICAN1 DAPPi-Lmulti, a canine combined vaccine, was tested after a primary course of two subcutaneous injections of one dose given 4 weeks apart to puppies aged from seven to nine weeks. Challenges with three pathogenic serovars of Leptospira spp. (Canicola, Icterohaemorrhagiae and Grippotyphosa) were carried out 14 days (onset of immunity studies – OOIs) and 13–15 months (duration of immunity studies – DOIs) after primary vaccination. During the four-week post challenge monitoring period, daily clinical observations were recorded, and blood (culture, biochemistry and haematology), urine (culture) and kidney (culture and histology) samples were collected regularly throughout the study or at necropsy. In OOIs, vaccination prevented mortality, clinical signs of the disease, infection, urinary excretion, renal carriage and renal lesions for all serovars. In DOIs, mortality, clinical signs and infection were less frequent in controls challenged with serovars Canicola and Grippotyphosa than in OOIs whereas they were absent or mild and transient in vaccinated dogs. Urinary excretion, renal carriage and renal lesions were at least significantly reduced in vaccinated dogs compared to controls for all serovars.These studies demonstrated that the tested vaccine provides a quick onset of immunity as early as two weeks post-vaccination and a long-term immunity of 13–15 months with full protection against fatal leptospirosis for serovar Icterohaemorrhagiae; prevention of mortality and clinical signs, and reduction of infection, urinary excretion, renal carriage and renal lesions for serovar Canicola; and prevention of mortality and reduction of clinical signs, infection, urinary excretion, renal carriage and renal lesions for serovar Grippotyphosa.