Serological responses of farmed red deer to a vaccine against Leptospira interrogans serovars hardjo and pomona

Abstract

Six adult, female, red deer were vaccinated with a hardjo-pomona vaccine followed by a second vaccination four weeks later and thereafter, at yearly intervals for two years. Serological responses were determined at intervals using a standard microscopic agglutination test. Increased responses to hardjo were observed in two deer which were seropositive to this serovar before vaccination compared to those which were initially seronegative.

Some initially seronegative deer developed titres to hardjo said pomona ranging from 1:24 to 1:48 following the first dose of vaccine, and all deer produced a serological response to both serovars ranging from 1:24 to 1:96 following the second vaccination except one animal which failed to produce a pomona titre of 1:24 or greater.

Responses to annual revaccinations were more variable both within and between years. Most deer produced titres which ranged from 1:24 to 1:96 for three to five months, although some deer failed to seroconvert following the annual revaccinations. Peak responses were similar to those recorded in cattle following an identical vaccination programme with the same vaccine but titres fell to undetectable levels after three to five months whereas titres reported in cattle generally persisted for at least 12 months.