Prevalence of Newcastle disease in Dongola area

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Ahmed Mohamed Zein, Zein
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This work was carried out on Newcastle disease in Dongola Province, Northern State. The aim of the work was to make field observations on the disease, carry out a serological survey to detect antibodies against the virus and to isolate and identify the virus from indigenous breeds. An outbreak of the disease occurred in the Province in April 2000, and heavy losses were encountered among local breeds. This was the only outbreak in the area during the period of this study. The infected chickens showed nervous signs, diarrhoea and respiratory signs such as nasal discharges and coughing. Eight isolates were recorded from 27 clinically sick birds and recovered from 78 tissues (brain, spleen and bone marrow) in embryonated chicken eggs. Five isolates were recovered from the brain, two from spleen and only one from bone marrow. Two isolates were lost, possibly due to repeated freezing and thawing that occurred during initial isolation attempts. All isolates agglutinated chicken RBC but not horse RBC indicating that they did not belong to the mild pathotype. Positive haemagglutination inhibition (HI) test confirmed the presence of ND. The isolates were identified by known ND antiserum using HI test. Four isolates and one virulent NDV (EI-Obied) strain were examined for pathogenicity, and on the bases of their Mean Death Time (MDT). Inrocerebral Pathogenicity Index (ICPI) and Intramuscular Pathogenicity Index (IMPI) and similarity in pathogenic properties to EI-Obied NDV isolate. They were considered velogenic NDV. Haemagglutination inhibition test showed that 38.3% of the birds possessed antibody to NDV and 61.7% did not reveal presence of NDV antibodies in their sera, and males showed high prevalence rate (58.6%), than females (31.5%). The prevalence of antibodies to NDV in sera of large baladi was 41.2% while it was 39.2% in Betwil, 35.9% in Fayomi and 34% in the Bare-necked baladi. Only 15% of the birds seemed to have antibody levels protective against NDV. Presence of ND antibodies in indigenous breed (unvaccinated), and isolation of the virus from them, indicated the endemic nature of the disease in Dongola.