Infectious bronchitis virus (IBV) is one of the foremost causes of a persistent economic burden to poultry industries worldwide IBV belongs to the genus Gammacoronavirus within the family Coronaviridae. The IBV infection leads to respiratory and nephrogenic symptoms in broiler chickens In addition, its infection leads to reduced fertility and hatchability in layer birds We determined the first complete genome sequence of a variant IBV from an outbreak in Haryana state of the Northern part of India using next generation sequencing. On phylogenetic analysis of the IBV isolate, it clustered with genotype I lineage 1 (GI-1). The deduced ammo acid sequence of S gene of IBV isolates showed a high level of identity with strains isolated from Tamil Nadu and the reference vaccine strains Our result suggests that the IBV virus isolated from unvaccinated chicken flocks in North India might be a revertant strain originally evolved from the live attenuated vaccine strains used in the region Determination of the complete genome sequence of additional IBV isolates from India is necessary to understand the epidemiology of IBV in India.

Thyroid hormones (THs) are involved in the development of lymphoid organs and regulation of immune function in birds. However, their role as an immune-modulator in the hyperthyroid state is still debatable. To explore the interrelationship of thyroxine (T-4) and the immune system, chicks were divided into three groups. Group I was comprised of control birds, who received the basal diet while group II and III were given diets supplemented with 5g and 10g thyroxine/kg feed, respectively, from 15 to 28days of age. Cell-mediated immune response was evaluated through in vitro abdominal macrophage phagocytosis assay, macrophage nitric oxide (NO) production, heterophil-to-lymphocyte (H:L) ratio and delayed-type hypersensitivity response against phytohemagglutinin (PHA). Humoural immune response was assessed through serum IgG and IgM antibody production against sheep red blood cells (SRBCs) and antibody production against infectious bronchitis virus (IBV). Sampling was carried out at 7, 14 and 21days of treatment. Results have shown higher levels (p<.001) of circulating T-4 in both treatment groups compared to the control group. There was a lower (p<.05) macrophage engulfment percentage, an increase in H:L ratio (p<.001) in treated birds, while their NO production remained higher (p<.05) in thyroxine supplemented groups after bacterial lipopolysaccharide stimulation. The humoural immune response revealed a significant decline (p<.001) in IgG, IgM antibody production against SRBCs but IBV circulating antibodies increased with age. In conclusion, hyperthyroidism has a strong co-relation with decreased immune performance of birds.