Efficacy of leptospiral commercial vaccines on the protection against an autochtonous strain recovered in Brazil.

In swine and bovines, leptospirosis prevention and control is carried out via vaccination of susceptible animals using bacterins. However, the efficiency of leptospirosis vaccines has been questioned. This work aimed to investigate the potency of five leptospirosis vaccines sold commercially in Brazil, challenging the animals with one autochthonous strain of Leptospira, Canicola serovar, denoted LO4, isolated from swine. The standard protocol was followed, and renal carriers of Leptospira were identified among the surviving animals by culture and PCR. Of the five vaccines tested, only two proved effective. None of the surviving animals was positive by culture; however, one animal was positive by PCR. Three of the five vaccines sold commercially in Brazil for the immunization of swine or bovines failed the test of the efficacy to protect the vaccinated animals following challenge with an autochthonous Leptospira strain, Canicola serovar. The two vaccines provided protection against the renal carrier state in the surviving animals. The criteria used to produce leptospirosis bacterins sold commercially in Brazil must be reviewed. The industry should support researches on leptospiral vaccinology to improve the quality of the present vaccines and discover new immunogenic strains, because it is known that vaccination is one of the most important tools to increase the reproduction rates in livestock.