A FIELD TRIAL OF THE HEAT-RESISTANT V4 VACCINE AGAINST NEWCASTLE-DISEASE BY EYE-DROP INOCULATION IN VILLAGE POULTRY IN CAMEROON

About 100 chickens in each of three Cameroonian villages were vaccinat ed against Newcastle disease by eye-drop with the V4 heat-resistant st rain and marked. In each of a further two villages another 100 chicken s were marked and mock-vaccinated as controls. Each village was visite d weekly for 18 weeks after vaccination, and all mortality and losses, sales and consumptions of the marked chickens were noted. A sample of about 20 serum samples was taken every 3 weeks from marked chickens i n each village for 15 weeks for titration of antibodies against Newcas tle disease. In the vaccinated villages a peak mean titre of greater t han log(2)5 was observed 3 weeks after vaccination; the mean titres re mained at least log(2)3 for 12 weeks after vaccination. There was no m ortality due to Newcastle disease in the vaccinated villages. In the c ontrol villages an average of 15% of the chickens died of Newcastle di sease during the observation period. Twenty weeks after vaccination a sample of ten study chickens was purchased from the vaccinated village s and ten were purchased from the control villages; these were challen ged with the velogenic Italien strain of Newcastle disease virus. Four out of ten of the vaccinated chickens and one out of ten of the non-v accinated chickens survived the challenge.