Avian mycoplasmosis in Asia.

Since 1954, avian mycoplasmosis has been considered a significant problem in chicken flocks in Japan and in other Asian countries. In Japan, Mycoplasma gallisepticum (MG) and M. synoviae (MS) infections were confirmed aetiologically in chicken flocks affected with respiratory disease or synovitis in 1962 and 1973, respectively. In other Asian countries, including Indonesia, the People's Republic of China, Korea, Malaysia, the Philippines, Taipei China and Thailand, the occurrence of mycoplasmosis in chicken flocks has been recognised serologically or aetiologically. Adverse atmospheric and environmental conditions, in addition to mixed infections of bacterial or viral origin, play an important role in the spread of MG and MS within chicken flocks or in the induction of clinical respiratory mycoplasmosis. Serological tests are important in determining and monitoring the mycoplasmal infection status of chicken flocks. The establishment of mycoplasma-free breeding stocks is recognised as essential for the control of avian mycoplasmosis. To eliminate the transmission of MG to the egg, treatment of infected breeder flocks or their progeny with anti-mycoplasmal antibiotics was effective in considerably reducing the infection rate but not in entirely eliminating MG infection. The preincubation heat treatment of chicken hatching eggs has proved an effective procedure for establishing MG- and MS-free breeding stocks in Japan. Vaccination against MG infection has been practised successfully in Japan and other countries.