“…The reader is also referred to other recent reviews on general aspects of MD (Nazerian et aI., 1976;Calnek and Witter, 1978;Nazerian, 1979Nazerian, , 1980Calnek, 1980) and on the more specialized topics of immunity (Witter, 1976;Sharma, 1978;Theis, 1979;Biggs, 1980;Powell, 1981), pathogenesis (Payne et aI., 1976), HVT (Prasad, 1979), and vaccination and other control methods (Biggs, 1975;Purchase, 1975Purchase, , 1976.…”