is troublesome because we know that it is difficult to diagnose before a post mortem is completed and there is no point in treating a deceased animal. therefore, producers often treat metaphylactically, or on suspicion of infection. tilmicosin can be added to the feed and has been shown to reduce the levels of h. somni in herds. it should only be added to the feed for 14 days, should be used sparingly as resistance is likely to occur otherwise, producers should be aware of withdrawal times. problems with antibiotic treatment is emerging resistance to tetracyclines, enrofloxacin, and florfenicol. biofilms that are formed by h. somni function to protect the bacteria from host immune defenses, they also provide a barrier that impedes antibiotic function. a new line of research is treating susceptible populations with bacterial isolates from subclinical carriers of histophilus somni to act like a probiotic bacteria for the respiratory tract. a nasal inoculation of a nonpathogenic strain of h. somni could allow for the respiratory tract mucosa to be colonized with the commensal bacteria. there are many licensed vaccines against h. somni, however licensed does not mean effective. there is a push to develop new vaccines that are multi-pathogenic and diva compatible. h. somni vaccines are usually killed cells or specific outer membrane proteins but have not been proven to be effective at protecting cattle against disease. there are many constraints to vaccine use on top of ineffectiveness, including the timeliness of administration, adverse reactions from individuals in the herd, and research into the epidemiology of the disease. in order to treat this infection, one must know which organ system it is effecting and some systems, such as the neurological presentation does allow for timely treatment because by the time the disease is detected, it is too late for treatment.