Ornithobacterium rhinotracheale is a Gram-negative bacterium of the rRNA superfamily V within the CytophagaFlavobacterium-Bacteroides phylum, which has become an emerging pathogen in the poultry industry. The purpose of this work is to review the current literature on O. rhinotracheale infection in domestic poultry. Despite the difficulties to identify the bacteria using biochemical tests, the polymerase chain reaction (PCR) technique has been successfully used to identify suspected isolates. Moreover, pulsed-field gel electrophoresis (PFGE) has allowed the genetic typing of O. rhinotracheale. Recent investigations carried out in the United States and Argentina described the unusual and extensive β-hemolytic activity of field strains isolated from affected chickens and turkeys. According to the latest serological studies, the causing agent has eighteen serotypes (A to R) and serotype A is the most prevalent among chicken and turkey strains. Gross findings typically found in broiler chickens are unilateral pneumonia, pleuritis, and abdominal airsacculitis with foamy, white yogurt-like exudate, which cause increased condemnation rates at slaughter, whereas those found in turkeys include tracheitis, pneumonia or bronchopneumonia, thoracic and/or abdominal airsacculitis, pericarditis, and peritonitis. Despite the worldwide efforts to control O. rhinotracheale infection, the present situation shows several problems not only because antibiotic treatments appear to be less effective due to the resistance acquired in the poultry industry but also because the vaccines developed so far show variable results in commercial poultry.

The aim of this study was to examine the histopathological and immunohistochemical changes caused by natural and experimentally-induced Ornithobacterium rhinotracheale infection in the respiratory system of chickens. To this end, three different studies were carried out. The first was a retrospective study of 82 field cases with respiratory disorders compatible with O. rhinotracheale infection. The bacterium was immunohistochemically detected in the lungs in 48 of 82 field cases, and 50 β-haemolytic (BH) and non-haemolytic (NH) strains were isolated. In the second study, an experimental model of the disease was created using 3week-old broiler chickens, to identify possible differences of pathogenicity between the BH and NH isolates by the intravenous (IV) and intratracheal (IT) inoculation routes (IR). The group challenged with the NH isolate showed more severe lung lesions than the group challenged with the BH isolate at 7-days postinoculation (p.i.). The 14-day p.i. groups challenged with either the BH or NH isolates by the IT or IV IR had a higher histologic grade of pulmonary and hepatic lesions and a higher total histologic grade of lesions suggesting more severe pathology with longer time of exposure. A direct association between the inoculation routes and the organs affected was shown. Finally, a slaughterhouse study was carried out from October 2014 to May 2015, in which the histologic grade of lesions was significantly higher in immunohistochemically positive for O. rhinotracheale lungs of dead-onarrival chickens.

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We characterized naturally occurring pigeon herpesvirus (PiHV; Columbid alphaherpesvirus 1) infection in domestic pigeons in California. We retrieved and analyzed 62 pathology reports produced between 1991 and 2014 at the California Animal Health and Food Safety Laboratory System. In 56 of the cases, the diagnosis of PiHV infection was established based on histopathology, either alone (44 cases) or combined with virus isolation (VI; 8), transmission electron microscopy (TEM; 3), or PCR (1); in the remaining 6 cases, the diagnosis was established based on VI (5 cases) or TEM (1) alone. PiHV infection affected 1 system in 34, 2 in 16, and ≥3 systems in 6 cases; data were not available for the remaining 6 cases. Most commonly affected was the digestive system (55 cases), followed by the respiratory tract (5) and lymphoid system (2). The liver (39 cases), crop (17), and esophagus (14) were the organs affected most commonly. Many affected cells often bore single eosinophilic intranuclear inclusion bodies. PiHV infection was a secondary diagnosis or incidental finding in 35 cases. Most (55) cases had 1 (21), or up to 4 (34), other concurrent infections; the most common concurrent infections were pigeon circoviral infection (26), trichomonosis (24), aspergillosis (11), and colibacillosis (10).