Further Studies on The Field Strains of Newcastle Disease Virus And The Estimation of The Degree of Immunity In Chickens During The Outbreaeaks

Newcastle disease causes very serious economic lOSfles in A,R.E. inspite of vaccination and had affected largemodern intensive broiler units and small poultry flocks.This was reflected in both economic losses to the breeders and a reduction in supplies of human food. The results achieved showed that: Eleven strains of NDV wepe isolated from outbreak~ of the diseafield Newcastle disease virus were examined for pricipita- tine, HI and neutralizing antibodies. 27 samples out of 170 showed pricip:i”tating antibodies of variable tlters. 11~ samples gave HI unt:i.body titers ranged from 1 : 16 to 1 : ~048 und 51 remainto 1/16. 1:h6 l.’esistanc’e to DVl challenge using a 100a1 velogenic V:f..l(US after Va~ination of Qhicks wit,tl ”F” strain under fielCl conditions DROP,ed f.:rom 30% protection at the,: 3rd week