Ornithobacterium rhinotracheale: A review.

Ornithobacterium rhinotracheale is a relatively recently discovered bacterium of the rRNA superfamily V. It is of worldwide distribution in commercial poultry, in which it is associated with respiratory diseases, and it is also found in wild birds. Airsacculitis and pneumonia are the most common features of infection with O. rhinotracheale. These signs can be induced by aerosol in intra-tracheal or intra-thoracic administration of the organism, and can be aggravated by other factors, such as respiratory viruses, bacteria or climatic conditions. Osteitis, meningitis and joint-infections, which can be induced by intravenous application, have been associated with O. rhinotracheale, but it remains uncertain whether the organism should be regarded as a primary pathogen. The infection can be transmitted horizontally by aerosol, as well as vertically through eggs, which probably accounts for its rapid and worldwide spread. Although O. rhinotracheale is difficult to identify, some commercial identification systems have been found to be suitable, although the media used in such systems will not always support its growth. A PCR assay was also found to be suitable for identification purposes. Twelve serotypes can be distinguished within the species O. rhinotracheale, of which serotype A is the most prevalent. Genetic investigation has revealed that more species or subspecies probably exist within the genus Ornithobacterium. Therapeutic treatment of the disease can be difficult because acquired resistance against the regular antibiotics is very common within the genus. Vaccination with autogenous inactivated vaccines has been successful in reducing clinical signs, but success depends on the adjuvant used. Only potent oil adjuvants are effective in young birds with maternal antibodies, but the use of these adjuvants is known to induce some local reactions. Live vaccination is feasible, but up to now, no avirulent strains of O. rhinotracheale have been found. Vaccination of broiler breeders induced protection against experimental infection of the progeny to at least 3 weeks of age.