MOLECULAR AND BIOLOGICAL CHARACTERIZATION OF WILD STRAIN OF DUCK PLAGUE VIRUS
Loading...
Date
2016-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Assam Agricultural University, Khanapara, Guwahati
Abstract
Duck plague or duck viral enteritis is an acute and contagious viral disease of ducks, geese swan and other waterfowl. The disease is responsible for significant economic losses in duck husbandry due to decrease in egg production, condemnation and mortality in duck.
The present study was undertaken to study the molecular and biological characterization of wild strains of duck plague virus. In the present study 6 wild strains of DPV (DP/As-Km/0010, DP/As-Nal/0012, DP/As-Km/0016, DP/As-Km/0019, DP/As-By/0022, DP/As-Km/0025) were revived in ducklings. All the inoculated ducklings developed distinct clinical signs like nasal discharge, lacrimation, pested eyelids, greenish watery diarrhea, soiled vents and sometimes sudden death etc. Post mortem examination revealed gross lesions in brain, oesophagus, liver, spleen, heart, bursa of Fabricious and in intestine. Presence of viral nucleic acid was detected by PCR and detection of duck plague virus antigen in post mortem samples was done with indirect FAT. All the isolates revived in ducklings were further propagated in DEF upto 5th serial passage. The clear CPE was observed from 1st passage onwards.
On the basis of DID50 and TCID50, a VV strain of DPV was selected for further study. DID50 of DP/As-Km/0019 was found to be 10-2 and DID50 in case of DP/As-By/0022 and DP/As-Km/0025 was 10-1. Highest TCID50 was found to be 106.33 in case of DP/As-Km/0019. On the basis of these parameters (DID50, TCID50). The strain DP/As-Km/0019 was selected as VV strain of DPV.
The pathodynamics of the VV strain was studied by using mean clinical and pathological scores and virus excretion pattern in blood and other clinical samples like tracheal swab and cloacal swab, nasal and ocular swab. Highest mean pathological score was observed in Liver and oesophagus (2.33±0.51) and lowest was observed in thymus and bursa (1.00±0.00).Molecular characterization of selected VV strain of DPV was done by sequencing two genes (UL30, US10) from different region of the virus. Phylogenetic analysis showed close relation with other isolates of DPV and vaccine strain. VNT50 titre of VV strain of DPV (DP/As-Km/0019) was found to be 1:223 which is similar to VNT50 of the vaccine strain and for other moderate virulent strains (DP/As-By/0022 and DP/As-Km/0025), VNT50 was 1:188 and 1:112 respectively.
The selected VV strain of duck plague virus was adapted in 9-11 days old embryonated chicken eggs. Different changes like thickening of CAM with extensive haemorrhages, Haemorrhage and congestion throughout the body of infected embryos were observed from 3rd passage onwards. The chicken embryo adapted VV wild strain of DPV was again adapted and propagated in the CEF upto 10th serial passage. The most common CPEs were rounding of cell, vaculation in the cell, syncytia formation and finally detachment of cell monolayer which was observed from 3rd passage onwards.
Description
Keywords
null