Ornithobacterium rhinotracheale Infection in Turkeys: Experimental Reproduction of the Disease

Abstract

This report details the first experimental production of clinical disease, mortality, and pathology resembling that of field infections by using Ornithobacterium rhinotracheale alone. Twenty-two-week-old male turkeys were exposed to O. rhinotracheale or lung homogenate from O. rhinotracheale-infected turkeys. Within 24 hr after inoculation, turkeys given O. rhinotracheale or lung homogenate intratracheally were depressed and coughing and had decreased feed intake. By 48 hr, several birds were coughing blood and ultimately died. Grossly, the lungs were reddened, wet, and heavy, failed to collapse, and were covered by tenacious tan-to-white exudate. Microscopically, the parabronchi and air capillaries were filled with fibrin, heterophils, macrophages, and small numbers of gram-negative bacteria. The pleura was often covered by a thick layer of fibrin, heterophils, and macrophages. Turkeys that survived to day 7 postinoculation had severe, subacute pneumonia. Ornithobacterium rhinotracheale was recovered from the lungs of most birds with pneumonia and was also cultured from the air sacs, sinuses, tracheas, spleens, and livers. All turkeys inoculated with O. rhinotracheale developed antibodies to O. rhinotracheale detectable by the serum plate agglutination test.

Synergy between avian pneumovirus andOrnithobacterium rhinotrachealein turkeys

“…These results corroborate with the findings of several researchers who likewise came across difficulties in producing respiratory signs in turkeys (Back et al ., 1997;De Rosa et al ., 1997;Jirjis et al ., 2004), but are in contrast with the results of other researchers. Some research groups did reproduce marked disease, occasionally evolving into death, following intratracheal and intrasaccular inoculation of ORT (Ryll et al ., 1996;Sprenger et al ., 1998). Also, van Empel et al (1996) were able to evoke clinical symptoms, albeit fairly mild (growth retardation and airsacculitis), after intra-air sacs and aerosol challenge.…”

“…In all experiments that were successful in reproducing acute clinical signs in turkeys, intratracheal or intrasaccular infection was applied (Ryll et al ., 1996;Sprenger et al ., 1998) and in this way the innate defence mechanisms situated at the upper respiratory tract are possibly bypassed. Other possible factors may be host related, with the age and health status as plausible determinants, although the occurrence of the disease does not seem to be correlated to a narrow age group */not in field outbreaks, nor under experimental conditions (De Rosa et al ., 1996;Hafez, 1996;Ryll et al ., 1996;Travers, 1996;van Empel et al ., 1996;Hinz & Hafez, 1997;Sprenger et al, 1998;van Veen et al ., 2000a). Noteworthy is the observation that, in all successful experiments, conventional turkeys were used instead of SPF animals.…”

“…At necropsy, however, no signs of septicaemia were noticed. ORT has in the past occasionally been isolated from the liver, spleen, kidney, ovary, oviduct, joints and brain after experimental infections Back et al ., 1998;Sprenger et al ., 1998;van Veen et al ., 2000b). Furthermore, pericarditis has been encountered under natural circumstances (Hafez, 1994(Hafez, , 1996van Beek et al ., 1994).…”

“…This organism is generally believed to be a facultative pathogen (Back et al ., 1997Franz et al ., 1997;van Empel et al ., 1999). However there are indications that ORT may be of primary importance (Ryll et al ., 1996;Travers et al ., 1996;van Empel et al , 1996;Sprenger et al , 1998). Some researchers believe that the different clinical outcome of ORT infections may be attributed to a variation in virulence .…”

Ornithobacterium rhinotracheale: A review

“…In other studies, airsacculitis, pneumonia and increased mortality were observed after aerosol, intra-tracheal, intravenous and/or intra-thoracic infection without a primer (Ryll et al, 1997a;Sprenger et al, 1998). In these studies, commercial birds were used, meaning that their microbiological and/or immunological status was uncertain, and may have contributed to the infections.…”