ABSTRACT
The genus Haemophilus is a member of the family Pasteurellaceae. The taxonomy of the genus has evolved rapidly with the availability of sensitive genotyping and protein analysis (Kuhnert and Christensen 2019). Of the current 13 species, nine with host specificity for humans are divided into three phenotypic groups: the H. influenzae group (H. influenzae, H. aegyptius, and H. haemolyticus), the H. parainfluenzae group (H. parainfluenzae, H. parahaemolyticus, H. paraphrohaemolyticus, H. pittnamiae, and H. sputorum), and a group comprising the single species H. ducreyi (Kuhnert and Christensen 2019; Norskov-Lauritsen 2014). Significant phenotypic and genotypic differences suggest that, while it currently remains a member of the genus, H. ducreyi would be more properly recognized as a distinct member of Pasteurella (Sturm 1981; Lagergard et al. 2011). Four species, H. felis, H. haemoglobulinophilus, H. paracuniculus, and H. parasuis, colonize and may be responsible for disease in animals. H. parasuis, however, will undergo reclassification and validation of as a new genus, Glaesserella parasuis, in the near future (Christensen and Bisgaard 2018; Dickerman et al. 2019).
