Devi Gopinath, Gauri Jairath, Birbal Singh and Gorakh Mal ICAR- IVRI Regional Station, Palampur H.P.
Infectious Bronchitis (IB) is a highly contagious viral infection affecting chicken of all age groups. The etiological agent is a Corona virus having multiple serotypes and genotypes. The disease is found all over the world and there are reports of the role of asymptomatic migratory birds in its transmission. It is a disease impacting the number as well as the quality of eggs and therefore the disease is having huge economic impact on the farmers. Moreover the recovered birds are left with permanently damaged reproductive tracts and they serve as virus shedders throughout their life. All these features reflect the impact of IB on both small and large scale poultry entrepreneurs.
Etiology and clinical signs
The Infectious Bronchitis Virus (IBV) is a Corona virus belonging to Gamma-corona virus group and infects only poultry. There is no evidence of human transmission of this virus till date. IBV is having almost 100% morbidity and 0-25% mortality rates. Transmission is through droplets of infected birds and material transmission because adult birds shed the virus through their droppings.
Even though the disease is not having any age barriers, young birds show most severe respiratory signs including coughing, sneezing, gasping, facial swellings etc. Adult birds’ clinical signs are less severe but they show reduced feed intake, deterioration in egg’s interior quality as well as permanent fall in egg production. Secondary bacterial infections complicate the condition and lead to mortality. Some nephropathogenic genotypes are also present and they cause diuresis, increased water consumption and death.
ELISA to detect elevated antibody levels, Haemagglutination Inhibition test (HI) and RT- PCR of nucleic acid extracted from various tissues like trachea, kidney. Diagnosis is better during the early onset of clinical signs.
Like many other viral diseases, IB is also not having any specific treatment. Antibiotic therapy is done to control secondary bacterial complications and they further reduces mortality. Supportive symptomatic therapy involves feeding highly proteinacious feed and electrolytes in water.
Even though live and killed vaccines are available against IB, multiple variants of the virus is a great hurdle to the immunologists. Day old chicks are vaccinated against IB world-wide. Recombinant vaccines targeting various antigenic variants of the virus will be a relief. Other than vaccination, identification and isolation of the infected chicken is utmost important to prevent the spread of disease. Other managemental practices to prevent mortality involves, well ventilated poultry houses, nutritious feed and elevated temperature of the houses etc.