Diagnostic Studies of Infectious Bronchitis Disease in Broilers using Pathological and Molecular Investigations in Kaliobeya Governorate, Egypt

Abstract

Infectious bronchitis (IB) is an acute, highly contagious viral disease of respiratory and urogenital system of chicken affecting all ages of both broilers and layers. It has a great economic loss to the poultry industry worldwide causing high mortality, poor body weight gain in broilers and decreased egg production in layers. The virus is transmitted by shedding of the viral particle in ocular and nasal discharge, as well as faecal droplets from infected poultry. Contaminated objects and utensils may play role in transmission of the virus from a flock to another [1]. Infectious bronchitis disease is caused by infectious bronchitis virus (IBV), an enveloped RNA virus. It has been classified under the Gamma Coronaviruses Genus within the Coronaviridae Family [2]. The IBV targets primarily the epithelial cells of the respiratory tract of the chickens [3]. The disease was reported firstly in 1931 in the USA as a respiratory disease [4]. Some IBV strains are nephropathogenic infecting kidneys and reproductive tissues [5].Chickens of all ages are susceptible to IBV infection; the severity of the disease is noticed in young chicks, compared to adults and resistance to infection increases with increasing the age. The morbidity rate can reach 100% but the mortality rate depends on the presence of secondary infections, immune status, flock age, environmental factors and management. In young chickens, the mortality rate is typically 25-30% but it can approach 80% depending on the virulence of the strain [1].Some strains of IBV cause acute nephritis and urolithiasis associated with the high mortality of infected chickens, more ever, the disease is a predisposing factor for secondary bacterial infection resulting in high mortality and morbidity rate [6]. Replication of IBV occurs primary in tracheal mucosa [7], after replication in tracheal mucosa, viraemia and secondary replication are found in other respiratory tissues as nose, lungs and air sacs and in non-respiratory tissues such as kidneys, gastrointestinal tract, oviduct, and testes [8]. Clinically, Abstract