Mycoplasmosis

Mycoplasma gallisepticum Infection Mycoplasma gallisepticum (MG) infections are commonly known as chronic respiratory disease (CRD) of chickens and infectious sinusitis of turkeys. M. gallisepticum diseases are characterized by respiratory rales, coughing, nasal discharge, and conjunctivitis, and frequently in turkeys, infraorbital sinusitis.

Transmission, Carriers, and Vectors Horizontal transmission occurs readily by direct or indirect contact of susceptible birds with infected clinical or subclinical birds resulting in high infection/disease prevalence within flocks. Vertical transmission (in ovo, transovarian) of MG is known to occur in eggs laid by naturally infected hens and has been induced following experimental infections of susceptible leghorn chickens.

Clinical Signs Chickens. The most characteristic signs of the naturally occurring disease in adult flocks are tracheal rales, nasal discharge, and coughing. Feed consumption is reduced, and birds lose weight. In laying flocks, egg production declines but usually is maintained at a lowered level.

However, flocks may have serologic evidence of infection with no obvious clinical signs In broiler flocks, most outbreaks occur between 4—8 weeks of age. Signs are frequently more marked than those observed in mature flocks. Severe outbreaks with high morbidity and mortality observed in broilers are frequently due to concurrent infections and environmental factors

Turkeys Turkeys are more susceptible to MG than chickens, commonly developing more severe clinical signs including sinusitis, respiratory distress, depression, decreased feed intake, and weight loss. As in chickens, more severe outbreaks with high morbidity and mortality frequently result with the involvement of complicating factors such as colibacillosis or environmental stressors.

Nasal discharge with foamy eye secretions frequently precede the more typical swelling of the paranasal (infraorbital) sinuses. Sometimes partial to complete closure of the eyes results from severe sinus swelling. Feed consumption may remain near normal as long as the birds can see to eat. As the disease progresses, affected birds become thin. Tracheal rales, coughing, and labored breathing may become evident if tracheitis or airsacculitis is present.

Turkey with advanced case of infectious sinusitis showing marked swelling of infraorbital sinuses and nasal exudate.

Turkey with advanced case of infectious sinusitis showing marked swelling of infraorbital sinuses and nasal exudate.

Gross Gross lesions consist primarily of catarrhal exudate in nasal and paranasal passages, trachea, bronchi, and airsacs. Sinusitis is usually most prominent in turkeys but is also observed in chickens and other affected avian hosts. Air sacs frequently contain caseous exudate.

DIAGNOSIS Isolation and Identification of Causative Agent Serology Differential Diagnosis: Newcastle disease or infectious bronchitis and E. coli, Infectious coryza, fowl cholera

INTERVENTION STRATEGIES Management Procedures Vaccination Nonliving M. gallisepticum Vaccines Live M. gallisepticum Vaccines

Treatment M. gallisepticum has shown sensitifity in vitro and in vivo to several antimicrobics including macrolides, tetracyclines, fluoroquinolones, and others but is resistant to penicillins or other antibiotics, which act by inhibiting cell wall biosynthesis. Tylosin has been injected subcutaneously at 3—5mg/lb body weight or administered at 2—3 g/gal drinking water for 3—5 days. Tiamulin and tiamulin plus salinomycin

Mycoplasma synoviae Infection

INTRODUCTION Mycoplasma synoviae (MS) infection most frequently occurs as a subclinical upper respiratory infection. It may cause air sac lesions when combined with Newcastle disease (ND), infectious bronchitis (IB), or both. At other times, MS becomes systemic and results in infectious synovitis.

ETIOLOGY Mycoplasma synoviae Natural and Experimental Hosts Chickens, turkeys, and guinea fowl (100) are the natural hosts of M. synoviae

Transmission Lateral transmission occurs readily by direct contact. Vertical transmission occurs in naturally and artificially infected chickens

Clinical Signs Chickens. The first observable signs in a flock affected with infectious synovitis are pale comb, lameness, and retarded growth. As the disease progresses, feathers become ruffled and the comb shrinks. In some cases, the comb is bluish red. Swellings usually occur around joints, and breast blisters are common. Hock joints and foot pads are principally involved, birds occasionally are found with a generalized infection but not with apparent swelling of the joints.

Turkeys. M. synoviae generally causes the same type of signs in turkeys as in chickens. Lameness is the most prominent sign. Respiratory signs usually are not observed in turkeys.

DIAGNOSIS Isolation and Identification Serology

INTERVENTION STRATEGIES Management Procedures Vaccination An inactivated, oil emulsion bacterin is commercially available, but its role in the control of MS has not been adequately studied. A live temperature- sensitive MS vaccine strain from field isolate is in use in Australia Treatment M. synoviae is susceptible in vitro to several antibiotics, including chlortetracycline, danofloxacin, enrofloxacin, lincomycin, oxytetracycline, spectinomycin, spiromycin, tetracycline, tiamulin, tilmicosin, and tylosin