Abstract
Background. In Italy an autogenous registered vaccine, adjuvanted with aluminum hydroxide, can be subministrated to contrast the Salmonella enteric subsp. enteric serovar abortusequi infection, coupled to a specific antimicrobic treatment.
Case description. Here we report the case of an abortion outbreak by Salmonella abortusequi in Central Italy, where mares were vaccinated but immediately developed a strong local reaction, maybe due to adjuvant. Promptly, a second dose of the autogenous vaccine, substituting the aluminum hydroxide with a new generation adjuvant (Montanide™ Seppic IMS 1313) in lower concentration, was administrated. The new formulated vaccine did not cause any adverse outcome and conferred high protection titers against the infection. As far as we know, this is the first reported case of immunization by a vaccine adjuvanted with Montanide™ Seppic IMS 1313 in horses, without adverse reactions.
Conclusions. This approach may be used as a preventive strategy for further outbreaks in association with the application of recommended biosafety principles.

Key words: Salmonella abortusequi; abortion; autogenous vaccine; Montanide™