Levamisole vaccine combinations. 1. Heightened antibody response

Levamisole was combined with a clostridial vaccine and experiments conducted in sheep to determine the effect on anthelminitic and vaccine efficacy. Vaccine potency was assessed in separate experiments in 200 sheep (divided into 5 groups). The individuals in each group were injected with one of the following 5 different preparations: levamisole combined with anaerobic vaccine at pH of either 3.5 or 6.0, vaccine alone at a pH of either 3.5 of 6.0, and levamisole alone. The combined levamisole/vaccine preparations had been stored for not less than 6 months prior to testing. A statistically-significant heightened antibody response to 5 antigenic components in the vaccine was obtained when the pH of the vaccine was reduced to 3.5 and the vaccine was given in combination with levamisole. This trend was present in the antibody response of the sheep when a pooled sample of the individual serums was tested at 6 weeks, 8 weeks and 14 weeks (8 weeks after the second injection). From the analysis of the individual serums at week 8 (2 weeks after the 2nd injection) there was evidence that the distribution curve of the titres had shifted to the right suggesting that the zero or poor responders in the population had improved immunocompetence, with the better responders also improving proportionately. The immunogenicity of the blackleg component was tested in sheep, 9 weeks and 32 weeks after the second injection and gave complete protection to a lethal challenge of Clostridium chauvoei. This combination offers not only increased ease of administration by providing a single anthelmintic and anaerobic vaccines injectable preparation (probably treatment with either or both is the two most common and important veterinary procedures undertaken by farmers, but in addition, the antibody titre of the treated animals is significantly increased. Part 2 of this paper establishes that the anthelmintic efficacy of the levamisole/vaccine combination was not impaired and that tissue reactions at the site of injection were acceptable.