Histophilus

Histophilus somni is a Gram-negative, pleomorphic, coccobacillus bacterium belonging to the family Pasteurellaceae. Three bacteria, Haemophilus somnus, Histophilus ovis and Histophilus agni, previously thought to be separate species, are now identified as being the same species as Histophilus somni. Histophilus somni is one of the bacterial agents commonly linked with bovine respiratory disease. Specifically it causes histophilosis.