Newcastle disease is caused by a virus belonging to the family of Paramyxoviridae; it is an avian paramyxovirus of serotype 1 (APMV-1). It affects wild birds and domestic poultry and usually presents as a respiratory disease. Depression, nervous manifestations, or diarrhea may also be the predominant clinical symptoms and mortality.
Gumboro disease, also known as infectious bursal disease (IBD), is a highly contagious disease of young chickens. Today, the very virulent form is predominant in most countries, and variant strains of IBD are present in several countries, leading to sub-clinical forms of the disease.