THE ISOLATION AND ATTENUATION OF A VIRUS CAUSING RHINOTRACHEITIS IN TURKEYS IN SOUTH AFRICA

a number of turkeys with severe respiratory symptoms affecting over 80 % of the flock were investigated for a possible causative agent. Wtth the standard techniques used for the isola-tion of bacteriae. mycoplasmae and viruses, only Mycoplasma gallisepticum, Mycoplasma meleagridis and Newcastle disease vtrus were isolated. Tracheal organ cultures were subsequently prepared from 27-day-old turkey embryos and inoculated with sinus exudate from affected turkeys. After an incubation period of 4 days a virus was isolated with which the typical symptoms, as observed in the field. could be reproduced in susceptible turkeys after 3-5 days. Following primary isolation in tracheal organ cultures. the virus grew readily in embryonated eggs and Ycro cells. With the electron microscope. virus-like particles, varying in size from 40 nm-500 nm, were observed, having a pleomorphic shape and studded with fine surface projections. The virus seems to fall into the family Paramyxoviridae. A vaccine pro-duced from attenuated virus in embryonated eggs afforded good protection against mortalities due to airsacculitis that normally follows on to turkey rhinotrachcitis infection. The serological and clinical effects of the virus on chickens arc also reported on