Haemophilus parasuis is a small, pleomorphic, NAD-dependent member of the family Pasteurellaceae. This bacterium is the etiological agent of Gl auml;sser rsquo;s disease in swine, which is characterized by polyserositis and arthritis. Once a sporadic disease, it has increased in prevalence and severity in recent years with the adoption of new production technologies which has led to pigs being susceptible to this infection. However, a lack of protective cross-immunity against some strains and ...