Different approaches to the vaccination of free ranging village chickens against Newcastle disease in Qwa-Qwa, South Africa

The aim of this study was to develop a strategy to control Newcastle disease (ND) in free ranging village chickens using the Nobilis® ND Inkukhu vaccine (Intervet South Africa). The study was conducted at Thibella village in Qwa-Qwa, South Africa from April 2001 to October 2002. Three different routes of vaccination (administration via eye-drop, drinking water and feed) were investigated. The haemagglutination inhibition (HI) test was conducted monthly in order to measure the antibody response of village chickens after immunization against Newcastle disease. Using a South African isolate of velogenic ND virus, challenge trials were conducted to determine the efficacy of the vaccine. A questionnaire was provided to evaluate perceptions of farmers on vaccinations. The eye-drop vaccination route produced the highest HI titres ranging between 2.7 and 4.4, followed by the drinking water vaccination route with titres ranging between 2.3 and 4.0. The lowest titres were from the feed vaccination route which ranged between 1.6 and 3.0. Following the challenge, the entire control group died on the third and fourth day after infection. However, 70% of the chickens immunized by using either the eye-drop or drinking water route survived the challenge. Only 20% of the chickens from the group immunized through the feed route survived. Evidently both the eye-drop and drinking water routes were efficient in preventing disease. Necropsies showed that vaccinated chickens had mild lesions whilst control chickens had severe lesions compatible with Newcastle disease. The efficacy of the vaccine using either of the routes can be enhanced by administration of booster vaccinations at 3-month intervals during the first year of a vaccination campaign and then at 6-month intervals from the second year onwards. The majority of the owners indicated that they would prefer to vaccinate their flocks using the drinking water route.