[01] Wegdan H., Veterinary Research Institute, Soba, Khartoum, Sudan. [02] Mahasin E., Veterinary Research Institute, Soba, Khartoum, Sudan. [03] Khalafalla A. I., Faculty of Veterinary Medicine, University of Khartoum, Khartoum North, Sudan.

Newcastle disease (ND) is one of the most important diseases in poultry worldwide. It is highly contagious affecting chickens other avian species and wild birds causing higher economic losses. vaccination is the best control strategy for the disease and many commercial live and killed vaccines being commonly used in poultry farms. In the present study, the effect of route of administration and dose on the immunogenicity and protective efficacy of the thermostable Newcastle disease vaccine (I²) was determined under Sudan field conditions. Three experiments were conducted to determine, firstly, the effect of routs of adminstration (namely intraocular (I/O), intranasal (I/N) and drinking water (D/W) and secondly, the dose of the vaccine (recommended dose and half, two and four times of the recommended dose) on the immunity of two weeks old commercial layer chicks under lab condition. In the third experiment, the immunogenicity of the vaccines I² “I/O, I/N and D/W” and Komarov “I/N and D/W” in three weeks old commercial layers and indigenous village chickens was determined under field condition. The results of the three experimental trials indicated that, protection against the challenge infection was attained when chicks received two doses of the I² vaccine via an intraocular route. The I/O route was found to be superior to the I/N which was confirmed to be better than the D/W route; as observed from the mean haemagglutination inhibition antibody (HI-Ab) titres and percentage of protection produced by the vaccine through these routes. When comparing the dose of the I² vaccine, it was proved that even half of the recommended dose resulted in good immune response and protection. Moreover, doubling or even four times of the recommended dose gave 100% protection without any adverse post vaccination reactions. Results of the field trials showed better Ab response of I² vaccine when given via an I/O route in three weeks old commercial layers and indigenous village chickens compared to K- vaccine of ND. Generally, at least HI antibody titre of 5.5 log² is required for 100% protection against challenge infection.

NDV, Thermostable Vaccine, Route, Dose, Safety, HI Test, Domestic Fowl, Sudan

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