Immunogenicity of a locally produced Newcastle disease I-2 thermostable vaccine in chickens in Uganda

A locally-produced Newcastle disease (ND) I-2 thermostable vaccine of embryo-infective dose (EID50) 10(8.5) per ml was administered to 100 laboratory chickens in four test groups, each of 25 birds. It was given by the eye-drop method, in drinking water, in drinking water freshly medicated with levamisole, or using millet grains as a vaccine carrier. A fifth control group consisting of 25 birds received the heat-sensitive La Sota vaccine (EID50 109 per ml) by the eye-drop method. The immunological responses were monitored by the enzyme-linked immunosorbent assay (ELISA) ND antibody technique using serum samples collected from 18 birds in each group at 3-week intervals for 3 months. The overall mean ND antibody log(10) titres and percentage positivities were 3.1, 88%; 2.9, 70%; 3.0, 83%; 3.2, 87% and 3.3, 87%, respectively. The use of water alone or medicated with levamisole for vaccine administration produced significantly lower ND antibody titres only in the first 3 weeks. The immunogenicity shown by the I-2 vaccine as a potential vaccine is discussed in relation to free-range poultry management conditions in Uganda.