99. 100. 101. MG is characterized by respiratory symptoms and a prolonged course of the disease. Particularly susceptible are hens and turkeys at all ages. The aetiological agent is M. gallisepticum. In many cases however, the pathogenicity of the microorganism is enhanced because of its association with any or some of the following agents: E. coli, P. multocida, H. paragallinarum and IB or ND viruses. The most characteristic signs in adult flocks are tracheal rales, nasal discharge, coughing, decreased egg production. Most outbreaks are in broiler chickens older than 4 weeks. The course of the disease is more severe during the winter and in cases of associated infections. Often, conjunctivrtes, facial skin oedema and profuse tear secretion could be observed.

102. In turkeys, unilateral or bilateral swelling of periorbital sinuses, nasal discharge and conjunctivitis are observed. The inflammatory exudate is commonly fibrinous and is detected as diffuse accumulation after removal of overlying skin.

103. 104.most common gross finding is aerosacculftes, the air sacs being filled with fibrinous caseous exudate. The majority of routine chemical disinfectants are effective against M.gallisepticum that rarely survives longer than a few days away from the host. The birds could carry the microorganism and be asymptomatic until the disease is triggered by stress factors such as change of the premise, the diet or weather, vaccinations against or infections with IB or ND, increased levels of dust or ammonia.

105.In older cases, the content of air sacs is dense and compact. A vertical transmission is done through the eggs of some unapparent carriers. The infected progeny transmits the agent horizontally via airborne route, by coughing or contaminated forage, water and environment.

106.Serofibrinous pneumonias, usually bilateral, are a frequent finding.

107Often, the inflammation involves the adjacent serous coats and thus, fibrinous polyserosites occur.

108Sinusites are relatively rarely observed in hens. The positive agglutination tests of sera in several birds from the flock confirm the diagnosis. MG should be distinguished from other respiratory diseases in poultry. Pulmonary and air sacs lesions could be mistaken with similar findings in E. coli septicaemia or aspergillus's. In turkeys, P. multocida pneumonia should also be considered.

109.110.Mycoplasma synoviae (MS) infections could progress as either acute or a chronic systemic disease with symptoms of arthritis, synovitis and bursitis especially in hens and turkeys. The earliest signs are lameness, lying down and retarded growth. Often, oedemas of tibiotarsal joints and the drumstick are observed. The morbidity and death rates are moderate, under 10%. Young chickens at the age of 4-12 weeks and turkey poults at the age of 10-12 weeks are susceptible. Synovites are encountered all year round, but are prevalent during cold humid seasons or when the litter is wet.

111.112.Affected birds get progressively exhausted. When the joints and tendon sheaths are open, a serofibrinous exudate is most commonly observed. The aetiological agent is M. synoviae. The microorganism shows a certain tropism to synovial structures as joints and tendon sheaths. An important route of dissemination of the agent is the transovarial trans-mission. The distribution by a horizontal route via the respira-tory tract is also possible. The commonly used means of diagnostics is ELISA. MS infections should be differentiated from staphylococcal infections, reoviral arthritis and RGT (see RGT).