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Articles by S.D. Singh
Total Records ( 3 ) for S.D. Singh
  Anjaneya , S.D. Singh , K. Dhama , M.Y. Wani , V. Gowthaman and M.M. Chawak
  Infectious Coryza (IC) is one of the highly infectious and contagious respiratory tract disease of poultry caused by Avibacterium paragallinarum. It has emerged as one of the major problem of commercial poultry industry worldwide due to huge economic losses in terms of increased number of culls and significant reduction in egg production (10-40%). Scarce reports are available regarding prevalence of Av. paragallinarum from India. The present study was designed to characterize the Indian Av. paragallinarum serovars at molecular level based on the Restriction Fragment Length Polymorphism (RFLP) of 16S ribosomal gene amplified, amplified 16S ribosomal DNA restriction analysis (ARDRA), sequencing of haemagglutinin antigen (hagA) gene and phylogenetic analysis. Four culture positive isolates of Av. paragallinarum, recovered from different geographical locations of the country, were confirmed by species specific HPG-2 Polymerase Chain Reaction (PCR) and other 10 nasal sinus swabs were found positive by direct HPG-2 PCR. ARDRA technique amplified product of 16S ribosomal DNA (r-DNA) showed identical Restriction Enzyme Analysis (REA) pattern for all the isolates indicating presence of similar operons in 16S ribosomal gene. The ‘hagA’ encoding a haemagglutinin antigen of Av. paragallinarum from all the field isolates revealed homology between Australian A and C serovar strain but did not cluster according to Page’s serovar scheme of classification. The present study is first in its nature regarding the molecular characterisation of Indian field isolates of Av. paragallinarum and provides valuable information regarding their genetic nature. Further extensive molecular studies will help both in the identification of field isolates and devising appropriate prevention and control measures for this important pathogen of poultry.
  K.A. Naveen , S.D. Singh , J.M. Kataria , R. Barathidasan and K. Dhama
  Newcastle Disease (ND) is a highly contagious infection of poultry which manifest in a wide range of severity from subclinical infection to lethal disease. In the past, a number of Newcastle disease outbreaks in poultry and other bird species have been ascribed to pigeon paramyxovirus type-1 (PPMV-1) infection. The conventional in vivo pathogenicity tests to assess the pathogenicity of PPMV-1 viruses have provided equivocal results. Lately, restriction enzyme analysis technique has been employed for unequivocal identification of individual strains of Newcastle Disease Virus (NDV) in poultry. In this study, sequence analysis of the F1/F2 cleavage site of the F gene of APMV-1 isolated from pigeons in India was attempted for pathotype prediction and determination of molecular epidemiology. Six pigeon origin NDV isolated in India between 1991 and 2001 were selected for this study. A portion of NDV F gene including the cleavage site was amplified by Polymerase Chain Reaction (PCR) and sequenced directly. The total number of nucleotide substitution among all six isolates ranged from 6 to 20; whereas, only four amino acid substitutions were observed. Nucleotides at position 304 and 357 were unique to all the pigeon isolates. The cleavage-activation site (380-397) had no nucleotide substitution and all the six pigeon isolates shared the amino acid sequence 112RRQKRF117 as that of velogenic viruses. The results of this molecular characterization study of Indian PPMV-1 isolates would help design better prevention and control measures for this important pathogen.
  V. Gowthaman , S.D. Singh , K. Dhama , R. Barathidasan , M. Asok Kumar , P.A. Desingu , N.K. Mahajan and M.A. Ramakrishnan
  Adenoviruses have been isolated from both clinically healthy and diseased birds worldwide. The pathogenic role of most of the FAdVs is still questionable. They can quickly take on the role of opportunistic pathogens when additional factors, particularly concurrent infections, adversely affect the health of the avian host. Immnosuppressing agents especially chicken infectious anemia and infectious bursal disease viruses are known to enhance the pathogenicity of FAdVs upon coinfection. The aim of the present study was to screen for the involvement of FAdV in poultry flocks affected with respiratory disease complex by RT-PCR. The samples were also screened by RT-PCR/PCR for other respiratory pathogens. Thirty two commercial poultry flocks with the history of respiratory disease complex from various parts of India. FAdV nucleic acid could be detected in tissue samples of 13 out of 34 farms investigated. Out of 13 FAdV positive farms, FAdV and CIAV were alone detected in 4/13 (31%) whereas, in other farms more than two respiratory pathogens were detected together. CIAV was detected in all the farms (34/34) investigated. Eosinophilic intranuclear inclusion bodies were noticed in FAdV infected laryngeal and tracheal epithelium under light microscopy. The findings of the study assert that FAdV can play the role of primary respiratory pathogen in immunocompromised birds and also in the presence of other respiratory pathogens.
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