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Kerala Veterinary and Animal Sciences University, Wayanad

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Subject: Microbiology × Author: VIDYA P. × End date: 2023 × Start date: 2020 ×
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    ThesisItemOpen Access
    MOLECULAR DETECTION AND CHARACTERISATION OF CHICKEN ANAEMIA VIRUS FROM KERALA
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR, KERALA VETERINARY AND ANIMAL SCIENCES UNIVERSITY, 2023-01-28) VIDYA P.; Dr. Surya Sankar
    Chicken anaemia virus (CAV) is the aetiological agent of chicken infectious anaemia (CIA), an immunosuppressive disease which brings huge economic burden to poultry industry globally. Epidemiology of the disease and virulence of the circulating strains is to be known, while formulating prevention strategies to any infectious disease. So far, there are no reports regarding the presence of CAV among the poultry flocks in Kerala. In this scenario, the present is envisaged for the detection of CAV, employing polymerase chain reaction (PCR) using primers targeting the VP1, VP2 and VP3 genes of the virus, and its characterisation by nucleotide sequencing followed by phylogenetic analysis. Out of 100 pooled tissue samples collected from suspected cases, 29 were found to be positive for CAV by PCR. Isolation of virus from tissue homogenate of PCR-positive samples in embryonated chicken eggs through yolk ac route inoculation was carried out. Embryos were harvested 14 days post inoculation and PCR using same primers was carried out to confirm the presence of virus, but none of the samples turned positive. All the 29 samples were positive PCR targeting VP1 and VP3 gene. The representative amplicons from direct PCR targeting VP1, VP2 and VP3 genes were sequenced, analysed and compared with sequences in GenBank. The isolates from Kerala exhibited variations of about one per cent among each other and about two per cent variations were noted with other Indian isolates. Phylogenetic analysis based on VP1 gene revealed that samples clustered each other and also with isolates from different parts of India and with the vaccine strains, Del Ros, 26P4 and Cux-1. On amino acid analysis of the three genes, the profile of VP2 and VP3 is conserved in nature, while VP1 exhibited similarities with rapidly spreading and highly pathogenic strains of CAV. Histopathologic examination of thymus, bursa of Fabricius and bone marrow of PCR positive samples, lesions indicating apoptosis of thymic cortex, lymphocytic depletion in bursa of Fabricius and atrophy and aplasia involving all haematopoietic lineages of bone marrow were observed.