Ornithobacteriosis, also known as Ornithobacterium rhinotracheale
(ORT) infection, is an acute, highly contagious bacterial disease of chickens. ORT is a rod-shaped, gram-negative, bacterium with several serotypes that is found in domestic and wild birds worldwide. ORT infection causes respiratory infections, such as airsacculitis
and pneumonia in affected birds. ORT can be a primary or secondary etiological agent, depending on the strain virulence, environmental factors, and immune status of the host, and the presence of other infectious agents. Outbreaks have been documented all over the world, including the USA, Asia, Europe, South America, Africa,, and the Middle East.
Clinical signs vary widely between individual birds and flocks, in addition to the severity and length of disease course of the infection. Concurrent infections with other pathogens also impact the range of clinical signs observed in flocks. For example, when chickens are infected with Mycoplasma gallisepticum
, concurrent infection with ORT often will increase the severity of clinical signs. In one study, chickens that were infected with both organisms developed keratoconjunctivitis and marked edema in their facial region, concentrating around their eyelids. Large masses of caseous exudate were found in their air sacs.
ORT is transmitted by horizontal and vertical routes. Chickens can become infected through direct and indirect contact through fomites, feed and water, or aerosols.
The incubation period from infection to when clinical signs develop varies between 1 to 4 days.
In central California, in the United States, between 2000 and 2012, ORT was isolated from 294 chickens and turkeys. In 82% of the chicken flocks, chickens were infected with ORT in addition to one or more respiratory pathogens. The most common gross lesions demonstrated in the infected chickens in the study were:
- Increased mucus in trachea
- Caseous or fibrinous exudate in the air sacs
- Consolidated lungs indicating pneumonia
- Congested and edematous lungs
- Flattened trachea
ORT infection occurs frequently in broilers and laying hens in China, resulting in 70% morbidity and 30% mortality in broilers.