Review Article
Tagesu Abdisa and Tolera Ta
Abstract
Newcastle disease is a contagious bird disease affecting many domestic and wild avian species and which can be transmissible to humans. It is caused by avian paramyxovirus serotype 1 virus which, with viruses of the other eight serotypes (avian paramyxovirus 1-9) has been placed in the genus Avulavirus, sub-family Paramyxovirinae, family Paramyxoviridae. Virulent Newcastle disease virus strains are endemic in poultry in most of Asia, Africa, and some countries of North and South America. Other countries, including the united states of America and Canada, are free of those strains in poultry. Highest prevalence of Newcastle disease is recorded in cross breeds of chickens than local breed and the low altitudes do have higher prevalence than the mid and high altitudes. The transmission of Newcastle disease occurs through respiratory aerosols, exposure to fecal and other excretions from infected birds, through newly introduced birds, selling and giving away sick birds and contacts with contaminated feed, water, equipment and clothing. The strain of Newcastle pathogenicity can be classified into five pathotype: Asymptomatic enteric strain; Lentogenic strain; Mesogenic stain; Viscerotropic velogenic strain and Neurotropic velogenic strain. Clinical signs are extremely variable depending on the strain of virus, species and age of bird, concurrent disease, and preexisting immunity caused by paramixovirus with worldwide distribution affecting chickens (all poultry and birds are susceptible) of All age group are susceptible. Symptoms from the respiratory tract are gasping, coughing, sneezing and rales. Signs from the nervous system include tremors, paralyzed wings and legs, twisted necks, circling, clonic spasms and sometimes complete paralysis. Other general symptoms that can be seen are greenish diarrhea, depression and inappetence, partial or complete drop in egg production and an increased production of deformed eggs. Clinical diagnosis based on history, signs and lesions may establish a strong index of suspicion but the laboratory confirmation must be done. The general approaches to the control of Newcastle disease are hygiene and vaccination. Humans are among the many species that can be infected by Newcastle disease in addition to avian species. Newcastle disease may cause conjunctivitis in humans, when a person has been exposed to large quantities of the virus. Mostly, Laboratory workers and vaccinators are affected. Recently, the disease which decreases the development of poultry production for industry is the infectious diseases, among infection disease Newcastle is the one which causes economical lose of poultry and its product. The objective of this review is to understand the Newcastle disease causative agent, pathogenicity, clinical sign and how to prevent and control the Newcastle disease, which concerned with the currently published or reported research.