DETERMINATION OF <i>IN-VIVO</i> GROWTH KINETICS OF VIRULENT NEWCASTLE DISEASE VIRUS IN BROILER CHICKENS

Abstract

The research work was conducted on 105 broiler chicks (Cobb-500) with a view to determine the rate of distribution of Newcastle disease virus (NDV) in various organs following infection through natural (intranasal, intraocular and oral) and parenteral (intravenous, intramuscular and subcutaneous) routes of inoculation at different ages (7, 15 and 28 days of old). Each bird received a dose of 0.2 ml of NVNDV (300 ELD₅₀). Body temperature, onset of clinical signs and mortality of birds (if any) were recorded daily. Blood samples were collected from the birds to determine the serum HI titre before and after infection. Faeces and various tissue samples (brain, lungs, kidney, colon, bursa of Fabricius, spleen and thymus) were collected daily following post-mortem examination of one bird from each sub-group to determine the presence of NDV along with their HA titre through inoculation into embryonated hen eggs. Some representative samples were also inoculated into chicken embryo fibroblast (CEF) cell culture for isolation of NDV. The highest body temperature (³108⁰F) was recorded in the birds of almost all the experimental groups between 48 and 72 hours of PI. Appearance of clinical sings was observed earlier (between 48 to 72 hours of PI) in parenterally infected birds than those of inoculated through natural routes. The shortest duration (>26-54 hours of PI) and longest duration (67-132 hours of PI) of death time recorded in birds those were inoculated through IV and oral routes of infection respectively. Isolation of NDV was positive from day 2 of PI and onward in all the groups with some minor variations in some cases. The CEF cell culture system was found more sensitive compared to avian embryo. Irrespective of routes of inoculation and age of birds, there was significant (p<0.01) increase in the mean HA titre of NDV with the progression of time. The highest HA titre of NDV was found in the brain tissue followed by lungs and kidney. Significantly (p<0.01) higher HA titre of NDV isolate was recorded in the birds of all the experimental groups inoculated through IV route. Following infection, the MDA titres decreased day by day in the birds with the increase of HA titres of NDV.