Actinobacillus seminis is a microorganism that infects the reproductive tracts of different ruminants, leading to economic losses in livestock due to low fertility, infertility, or abortions in female-infected animals. The lack of secure diagnostic tools, pathognomonic disease characteristics, and vaccines makes it challenging to control those infections. Knowledge of pathogenicity mechanisms and virulence factors could permit us to count on valuable tools to control diseases caused by this bacterium.