Early detection of tracheal damage in chickens by scanning electron microscopy.

Fifteen-day-old chickens were inoculated with effective doses of cultured Mycoplasma gallisepticum and treated with the antibiotic tiamulin or tylosin. Scanning electron microscopy was used to detect early and late damages in the tracheal mucosa of the affected birds. Edematous changes of various degrees were demonstrated as early as day 4 postinoculation. Catarrhal changes were observed at day 10 postinoculation, and obstruction of the tracheal lumen by mucofibrinous plugs was observed at day 10 or later postinoculation. Scanning electron microscopy was useful in early detection of inflammatory changes in the trachea of apparently healthy chicks.