CHAPTER ONE

Newcastle disease (ND) is one of the most important avian viral diseases because of its high economic impact on the poultry industry. Newcastle disease was discovered in Newcastle upon Tyne. Newcastle upon Tyne is a city and a metropolitan borough of Tyne and wear, in northeast England in 1926 (Doyle, 1927), but at this time slightly different strains were found in other parts of the world. The disease was initially reported in 1925 in Southeast Asia (Alexander, 1997) since then it has become an economically important disease of poultry all over the world.

Nigeria is the most populous country in Africa and is home to about 175 million domestic poultry. Poultry production in Nigeria can be classified into extensive and intensive systems. The extensive system accounts for the vast majority of poultry, more than 143 million which are free ranging birds in the rural areas (Sainbury, 2000). In Nigeria it is estimated that poultry supplies about 10% of the total meat needs and out of about 150 million poultry birds, 102 million are indigenous (Majiyade and Lamorde, 1997). The indigenous village chicken is identified as a way of providing rural women with diverse income earnings and employment (Alexander, 2001).