COMPARISON OF SOME LAIIORATORY TECIINIQUES ' USED FOR THE DIAGNOSIS OF ECONOMICALLY IMPORTANT POULTRY DISEASES

Abstract

This study included a field survey to determine the extent of prevalence of Infectious bursal disease (IBD) in different types of chickens in some of the heavily poultry producing areas in Egypt.

The field survey covered the losses caused by the disease, serological monitoring of maternally derived antibodies in newly hatched layer chicks and their persistence.

The relationship between the vaccination programs adopted in the investigated farms and the losses occurring due to the disease was also investigated.

The experimental work covered the rate of decline of maternally derived antibodies for both IBD and ND in day-old chicks derived from vaccinated parent flocks. The immunogenicity and immunosuppressive effects of an IBD intermediate vaccine as well as the protectiveness and serological effects of an inactivated one .

Evaluation of these criteria was perfonned by laboratory techniques namely; virus isolation, AGPT, ELISA and HI tests.

The following results were obtained:

• Serological surveying of commercial day-old layer chicks revealed great variation in the presence of maternally derived antibodies (MDA). The percentage of positive precipitating antibodies among them ranged from 60-96.6% in 13 investigated white and brown layer flocks.

• Despite the multiple application of live IBD vaccination (2-5 times), most investigated flocks suffered heavy mortalities (3-79%) in layers, (7-22%) in broilers and (18-29%) in baladi chickens due to the disease.

• IBD precipitinogens in bursal homogenates from 85% of the investigated flocks were detected successfully as soon as the signs of the disease appeared, while they are detected with difficulty later on in the course of the disease.