IMPORTANT VIRAL DISEASES ASSOCIATED WITH MORTALITY OF LAYER CHICKENS IN COMMERCIAL POULTRY FARMS IN BANGLADESH

Abstract

Disease profile investigation on 1751 dead chickens supplied from about 100 commercial large or small scale poultry farms of Gazipur district and surrounding area in Bangladesh during one year period from January to December 2002 at the BRAC Poultry Disease Diagnostic Centre, Nagapara, Gazipur showed that 22.73% (n = 398) cases with five different viral diseases, of which infectious bursal disease (IBD) (n = 196) and Newcastle disease (ND) (n = 181) showed significantly (p < 0.01) higher rate of occurrence than infectious bronchitis (IB) (n = 6), avian leukosis (AL) (n = 6) and fowl pox (FP) (n = 4). Age-wise occurrence of IBD showed highest infection rate in growing stage (82.65%) in comparison to brooding (3.06%), pullet (6.12%) and adult layer (8.16%) chickens. Although more or less all age groups of chickens were affected by ND (1.66% to 50.83%) but it was found significantly (p < 0.01) highest in adult (50.83%) chickens. Infectious bronchitis was recorded only in adult chickens. Avian leukosis was found higher in pullet (66.67%) than the adult (33.33%) layer birds. Fowl pox also recorded only in pullet stage of chickens. Seasonal influence showed significantly (p < 0.01) highest occurrence of IBD during summer (44.39%) in comparison to rainy (30.61%) and winter (25.00%) seasons. Similarly ND was recorded more or less uniformly in all the three seasons of the year with significantly (p < 0.01) higher rate during summer (41.99%) season. Infectious bronchitis was recorded significantly (p < 0.01) higher in summer (63.66%) season while avian leukosis was recorded in winter (66.67%). Fowl pox was found equally in winter and summer seasons (50%). Although IBD was found with other concurrent infection e.g., dual (23.98%) and triple (2.55%) types of infection but highest occurrence was recorded as a single type (73.47%) of infection. ND was found with dual (44.75%), triple (7.18%) and fourth (1.10%) types of infection but specially single infection (46.96%) were associated with high mortality. IB was recorded highest in single infection (54.55%) in comparison to dual (9.09%), triple (18.18%) and fourth types (18.18%) of infection. Avian leukosis was recorded higher as a single infection (83.33%) than dual (16.67%) type of infection. Fowl pox was recorded equally (50%) as single and triple types of infection. It may be concluded that both the single and concurrent infection of viral diseases, greatly influenced by season and age associated with high mortality, should be considered during vaccination programme, diagnosis, prevention and control.