Chronic Respiratory Disease

Chronic Respiratory Disease

Introduction

Infection with Mycoplasma gallisepticum is associated with slow onset, chronic respiratory disease in chickens, turkeys, game birds, pigeons and other wild birds. Ducks and geese can become infected when held with infected chickens. In turkeys it is most associated with severe sinusitis (see separate description in the turkey section). The condition occurs worldwide, though in some countries this infection is now rare in commercial poultry. In others it is actually increasing because of more birds in extensive production systems that expose them more to wild birds. 

In adult birds, though infection rates are high, morbidity may be minimal and mortality varies. 

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, airborne dust and feathers, and to a lesser extent fomites. Spread is slow between houses and pens suggesting that aerosols are not normally a major route of transmission. Fomites appear to a significant factor in transmission between farms. 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. Intercurrent infection with respiratory viruses (IB, ND, ART), virulent E. coli, Pasteurella spp. Haemophilus, and inadequate environmental conditions are predisposing factors for clinical disease.

Other Names

 CRD, air sac disease, airsacculitis

Organism or Mechanism

 Mycoplasma gallisepticum bacteria

Post-mortem lesions

• Airsacculitis.
• Pericarditis.
• Perihepatitis (especially with secondary E. coli infection).
• Catarrhal inflammation of nasal passages, sinuses, trachea and bronchi.
• Occasionally arthritis, tenosynovitis and salpingitis in chickens.

Diagnosis

Lesions, serology, isolation and identification of organism, demonstration of specific DNA (commercial PCR kit available). Culture 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 immuno-flourescence.

Serology: serum agglutination is the standard screening test, suspect reactions are examined further by heat inactivation and/or dilution. Elisa is accepted as the primary screening test in some countries. HI may be used, generally as a confirmatory test. Suspect flocks should be re-sampled after 2-3 weeks. Some inactivated vaccines for other diseases induce 'false positives' in serological testing for 3-8 weeks. PCR is possible if it is urgent to determine the flock status.

Differentiate from Infectious Coryza, Aspergillosis, viral respiratory diseases, vitamin A deficiency, other Mycoplasma infections such as M. synoviae and M. meleagridis(turkeys).

Preventive Measures

 • Purchase Mycoplasma-free birds (only from NPIP participants).
 • Practice good sanitation because it lasts on hands, clothes, and boots for several hours.
 • Avoid mixing poultry of different ages.
 • Avoid dust, chilling, and poor ventilation.
 • Prevent rodent infestation.
 • Prevent stress and ensure good nutrition.

Management Treatment

 • Provide warm, draft-free housing with proper ventilation.
 • Move birds to a clean environment.

Physical Treatment

Nutritional Treatment

Herbal Treatments

Homeopathic Treatments

 • If sneezing, coughing give--Antim trat, Belladona, Ars alb.
 • If water from eyes give--Euphrasia, Arg nrt.
 • If water from nose give--Allium cepa, Ars alb.
 • If white diarrhea give--Calc carb.
 • Combination remedy of Thuja200+Nat sulf200+Carbo veg200+Bryonia200, 5ml each in 8 liters of water for 100 birds for 3 days.