Species affected: Chickens and turkeys. Breeder birds especially affected. Age affected: All ages, especially older birds .
Causes: Gram-negative, non-sporulating rod shaped bacterium, Ornithobacterium rhinotracheale. Recently isolated, formerly known as a Pasturella-like organism, Kingella or Taxon 28.
Effects: Broilers and broiler breeders (24 to 52 weeks of age) show slightly increased mortality, decreased feed intake, mild respiratory signs. Hens show decreased egg production, poor egg shell quality and decreased egg size. In young chickens, coughing, sinusitis, and sometimes respiratory distress and oedema of the head are seen, leading to increased mortality and higher condemnations at processing.
The bacterium Ornithobacter rhinotracheal (ORT) was only identified in the 1990s, but has received much attention since. Twelve different serotypes of ORT are known. The disease is an acute, contagious respiratory disease of chickens and turkeys. The course and duration of the disease depend on such factors as climate, stocking rate and other simultaneous infections.
ORT is often isolated from chickens without obvious clinical signs. Clinical signs are coughing, nasal discharge and sinusitis. Sometimes there is respiratory distress and oedema of the head. In broiler breeders, clinical signs are usually observed early in the production period and consist most importantly of a decrease in egg production of 2-5%, lower egg weight and poor eggshell quality. In broilers, ORT infections occur between 3 and 6 weeks of age, and clinical signs are nasal discharge, sneezing, facial oedema, depression, increased mortality and low growth. Increased slaughterhouse condemnations may occur.
At postmortem, clinically diseased birds may reveal various gross lesions including rhinitis, sinusitis, tracheitis, airsacculitis, pneumonia, pericarditis, and arthritis. Foamy or cheesy exudate in the air sacs is often seen and is an indication for ORT.
In vitro, ORT bacteria grow rather slowly and need special growth conditions such as 5-10% CO2. ORT may therefore easily be overgrown by other bacteria that are present, such as E. coli. Suspected chickens should therefore be sampled early in the disease. The addition of gentamicin and polymyxin to the medium contributes to a more selective isolation of ORT.
Some antibiotics are effective.