Mycoplasma gallisepticum is an avian respiratory and reproductive tract pathogen, which has a significant economic impact on all sectors of the poultry industry worldwide. It is a persistent, highly transmissible chicken and turkey pathogen. M. gallisepticum belongs to the class of Mollicutes evolved from AT-rich, gram-positive bacteria. The class Mollicutes is different from other bacteria in its very small size and total absence of cell wall which accounts for its characteristic “fried egg” type of colonial morphology, complete resistance to antibiotics that affect cell wall synthesis, and its complex nutritional requirements due to its small genome size. Mycoplasma gallisepticum infection is of continuing economic concern in commercial broiler breeder chicken and meat turkey flocks, despite the great efforts of poultry industries made towards eradication of pathogenic mycoplasmas from poultry flocks. M. gallisepticum infection is a contagious, notifiable disease to the World Organization for Animal Health (OIE). Major clinical signs observed in avian M. gallisepticum infection include coughing, rales, sneezing, nasal discharges, airsacculitis and poor growth. Turkeys typically experience more severe disease, often accompanied by swelling of the paranasal (infraorbital) sinus. Conjunctivitis with frothy ocular exudates is common in turkeys and occurs occasionally in chickens. The symptoms of avian mycoplasmosis are typically slow to develop, and the course of the disease can be prolonged. However, acute respiratory disease sometimes occurs in young birds. More frequently the severity of the disease is characterized by the degree of secondary infection with viruses and/or bacteria such as Newcastle disease, infectious bronchitis, and Escherichia coli in chickens. In this paper, M. gallisepticum and its effects on the poultry industry are discussed.
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