Oral Newcastle disease vaccination trials in Ethiopia.

Vaccination experiments were carried out in Ethiopia to study the efficacy of the NDV-I(2) vaccine against challenge with an Ethiopian velogenic strain of NDV. In experiment A, which comprised 300 broiler chicks, the efficacy of the ocular/drinking water application of the HB1/La Sota vaccine was compared with the ocular/drinking water and the feed application of the NDV-I(2) vaccine on untreated barley and sorghum. The NDV-I(2) vaccine applied by eye-drop or drinking-water protected the chickens against challenge as efficiently as combined HB1/La Sota vaccination but untreated barley and sorghum were unsuitable vaccine carriers. The vaccine virus could not be recovered and chickens neither seroconverted nor were they protected. In experiment B, 120 broiler chicks were divided into 6 treatment groups. One group each received NDV-I(2) vaccine mixed with untreated barley or sorghum which was applied immediately, or 14h after mixing and standing at ambient temperature. The fifth group was vaccinated intraocularly and via the drinking water with the NDV-I(2) vaccine. The sixth group remained untreated. Experiment B confirmed the results of experiment A. In experiment C, 100 chicks were divided into 5 groups of 20 chickens each. One group each received the NDV-I(2) vaccine on parboiled barley or sorghum as vaccine carriers 0 and 6h after mixing. The last group remained untreated. Parboiled barley given 0 or 6 h and parboiled sorghum given 0 h after mixing with the vaccine led to seroconversion and protection of the chickens. Parboiled sorghum given 6h after mixing with the vaccine did not. It is concluded that the thermostable NDV-I(2) vaccine may be a suitable vaccine for oral application under Ethiopian conditions.