In Psittacine birds, a chronic infection may develop in the kidneys with potential for long-term shedding. ND is present in most countries but pathogenic strains are exotic to Canada and the U.S.A. ND has been reported in wild birds in Canada in 1995. In litter it can survive for 20 days, and in water, soil, carcasses, eggs and feathers for 255 days. Mechanical transmission between premises can occur on footwear, clothing, skin, feed, trucks, and poultry or egg handling equipment. In chickens, outbreaks may be so severe that almost all of the affected flock may dies within 72 hours without showing clinical signs.
Canaries generally show a mild disease with low mortality.
Most infections are in laboratory personnel. Pathogenic strains of ND cause sudden onset of depresssion, rapid breathing and anorexia in all ages of birds, and a sharp drop in egg production in laying hens. The viscerotropic pathogenic strain may cause edema of the head and bright green or bloody diarrhea as prominent clinical features. Pathogenic strains are exotic in commercial poultry operations in Canada.