Introduction

A slow onset chronic respiratory disease of turkeys often with severe sinusitis and associated with Mycoplasma gallisepticum infection. It is seen worldwide, though in many countries this infection is now rare in commercial poultry. Morbidity is low to moderate and mortality low.

The route of infection is via the conjunctiva or upper respiratory tract with an incubation period of 6-10 days. Transmission may be transovarian, or by direct contact with birds, exudates, aerosols, and fomites. Recovered birds remain infected for life; subsequent stress may cause recurrence of disease.

The infectious agent survives for only a matter of days outwith birds, although prolonged survival has been reported in egg yolk and allantoic fluid, and in lyophilised material. Survival seems to be improved on hair and feathers. Stress, malnutrition, intercurrent viral disease such as Newcastle disease (even lentogenic) and Turkey Rhinotracheitis are predisposing factors.

Signs

• Coughing.
• Nasal and ocular discharge.
• Swollen sinuses.
• Slow growth.
• Leg problems.
• Stunting.
• Inappetance.

Post-mortem lesions

• Swollen infraorbital sinuses, often with inspissated pus.
• Airsacculitis.
• Pericarditis.
• Perihepatitis.

Diagnosis

Lesions, serology, isolation and identification of organism, demonstration of specific DNA (commercial kit available). Culture, of swabs taken from the trachea or lesions, requires inoculation in mycoplasma-free embryos or, more commonly in Mycoplasma Broth followed by plating out on Mycoplasma Agar. Suspect colonies may be identified by immunofluorescence.

Serology: serum agglutination is the standard screening test, suspect reactions are examined further by heat inactivation and/or dilution. HI may also be used. Suspect flocks should be re-sampled after 2-3 weeks. Some inactivated vaccines induce 'false positives' in serological testing. PCR is possible if it is urgent to determine the flock status. Differentiate from viral respiratory disease, especially Turkey Rhinotracheitis.

Treatment

Tilmicosin, tylosin, spiramycin, tetracyclines, fluoroquinolones. Effort should be made to reduce dust and secondary infections.

Prevention

Eradication of this infection has been the central objective of official poultry health programmes in most countries. These are based on purchase of uninfected poults, all-in/all-out production, and biosecurity.

In some circumstances preventative medication of known infected flocks may be of benefit.