Ornithobacterium rhinotracheale, or ORT, is a contagious respiratory disease caused by a gram-negative bacterium that primarily affects turkeys and other poultry. Infections can lead to widespread illness, mortality, and notable decreases in production metrics, representing a significant economic concern. The bacterium was first identified as a distinct disease in turkeys in the early 1990s and has since become a recognized pathogen worldwide.
How ORT Spreads in Turkeys
ORT spreads readily within turkey flocks through several routes. Direct bird-to-bird contact is a common way for the bacteria to spread, especially in densely populated commercial housing. The bacterium can become airborne through coughing and sneezing, leading to aerosol transmission that can quickly infect many birds within the same airspace.
Indirect contact is another pathway for the disease. Contaminated feed, water sources, and bedding can harbor the bacteria, which has been shown to survive for extended periods in colder environments. Equipment, vehicles, and the clothing and footwear of farm personnel can act as fomites, carrying the bacterium between different houses and farms. Wild birds can also act as carriers, and vertical transmission from infected hens to their offspring through eggs can occur.
Symptoms of an ORT Infection
The clinical signs of an ORT infection in turkeys can vary in severity, influenced by the birds’ age and the presence of other diseases. Respiratory distress is the main indicator, and signs include coughing, sneezing, and audible tracheal rales, which are rattling sounds from the windpipe. Nasal discharge is common, and some birds develop foamy eyes or swollen sinuses, a condition known as “raccoon eye”.
Infected turkeys also show general symptoms of illness. Lethargy, depression, and huddling together for warmth are observed. Birds will have reduced feed and water consumption, which contributes to poor growth rates. In older turkeys, clinical signs can be more severe and may include weakness and cyanosis, which is a bluish discoloration of the head.
Diagnosing ORT in a Flock
A definitive diagnosis of ORT requires a veterinarian’s evaluation and laboratory analysis. The process begins with an on-site evaluation of the flock, where a veterinarian assesses clinical signs and the farm’s health history. The presence of respiratory symptoms and increased mortality, especially in turkeys between 12 and 20 weeks of age, may lead to a suspicion of ORT.
To confirm the diagnosis, samples are collected for laboratory testing. Veterinarians may take tracheal swabs from live birds showing symptoms. These samples can be used for bacterial culture to isolate and identify the slow-growing organism. More rapid molecular methods, such as Polymerase Chain Reaction (PCR) tests, can also be used to detect the bacterium’s genetic material. Post-mortem examinations, or necropsies, are also a diagnostic tool, as they can reveal characteristic internal lesions like severe pneumonia and airsacculitis.
Treatment Approaches for Infected Birds
Once a flock is diagnosed with ORT, treatment involves antibiotics. However, effectiveness can be variable due to antibiotic resistance. For this reason, an antibiotic sensitivity test, known as an antibiogram, should be conducted using isolates from the infected flock. This test helps a veterinarian select the most effective medication for the specific strain of bacteria causing the outbreak.
Antibiotics are administered to the entire flock at once, often through the drinking water or feed. Amoxicillin and tetracycline are examples of antibiotics that have been used to treat ORT infections. Alongside medication, supportive care is an important component of managing an outbreak, including measures to reduce environmental stress by ensuring proper ventilation, maintaining dry litter, and providing easy access to fresh feed and water to aid in recovery.
Flock Prevention and Biosecurity
Preventing ORT infections relies on strict biosecurity protocols. Implementing an “all-in, all-out” management system, where entire barns are emptied, cleaned, and disinfected between flocks, is a key practice. Controlling traffic onto the farm is another measure, including limiting visitors and vehicles that could introduce pathogens. Farm personnel should use dedicated clothing and boots and follow disinfection procedures before entering poultry houses.
Preventing contact between commercial flocks and wild birds is another part of biosecurity. Vaccination is an effective tool in a prevention program, and commercially available inactivated vaccines can be administered to turkey poults to help build immunity against the disease. Good environmental management, including maintaining optimal air quality through proper ventilation and keeping litter dry, helps reduce bird stress and lowers the pathogen load in the environment.