Duck plague is an enveloped DNA virus that belongs to the Anatid Herpes Virus; the Herpesviridae family is an acute and highly infectious duck, geese, and swan disease that causes tremendous economic losses of duck rearing in Bangladesh and other duck rearing countries. Therefore, we decided to isolate duck plague virus from recent fields’ outbreaks area and performed molecular detection and phylogenetic analysis to find out the similarities between our findings and other isolates around the world. Visceral organs of 13 suspected ducks from recent outbreaks area were collected by post-mortem examination for inoculum preparation. Several passages were performed to harvest into 9-11 old embryonated eggs Chorioallantoic membrane (CAM) route and duck embryo fibroblast (DEF) primary cell culture. DNA polymerase (446bp) and DNA polymerase (UL, 602bp) genes were used for molecular detection by Polymerase chain reaction (PCR). Pathogenicity was done with duckling and TCID50 on DEF. Molecular characterization was performed from extracted DNA of duckling and 2 Positive PCR products were partially sequenced for phylogenetic analysis of their origin and nucleotide variations. Sequenced data was analyzed to reveal genetic relationships among constructed phylogenetic tree for understanding potential transmission with origin of virus and data was then submitted to gene bank and got accession number for DPV-BR1-MN937272 and DPV-BR-2-MN937273. Among 13 samples, 4(30.77%) were found positive by PCR using DNA polymerase at 446 bp and UL at 602 bp gene. Chorioallantoic membrane (CAM) was observed hemorrhagic after 72 days and duck embryo fibroblast (DEF) become round as showed cytopathic characteristics after 48h of infection .Duckling showed that isolated virus was highly pathogenic as characteristics signs of post-mortem examination. Therefore, this has found that recent isolates have similarity with Bangladesh, India and China isolates. Moreover, TCID50 has confirmed the isolates have accepted titer to be a vaccine strain. Res. Agric., Livest. Fish.8(1): 125-133, April 2021
The research work was conducted on 105 broiler chicks (Cobb-500) with a view to determine the rate of distribution of Newcastle disease virus (NDV) in various organs following infection through natural (intranasal, intraocular and oral) and parenteral (intravenous, intramuscular and subcutaneous) routes of inoculation at different ages (7, 15 and 28 days of old). Each bird received a dose of 0.2 ml of NVNDV (300 ELD50). Body temperature, onset of clinical signs and mortality of birds (if any) were recorded daily. Blood samples were collected from the birds to determine the serum HI titre before and after infection. Faeces and various tissue samples (brain, lungs, kidney, colon, bursa of Fabricius, spleen and thymus) were collected daily following post-mortem examination of one bird from each sub-group to determine the presence of NDV along with their HA titre through inoculation into embryonated hen eggs. Some representative samples were also inoculated into chicken embryo fibroblast (CEF) cell culture for isolation of NDV. The highest body temperature (³1080F) was recorded in the birds of almost all the experimental groups between 48 and 72 hours of PI. Appearance of clinical sings was observed earlier (between 48 to 72 hours of PI) in parenterally infected birds than those of inoculated through natural routes. The shortest duration (>26-54 hours of PI) and longest duration (67-132 hours of PI) of death time recorded in birds those were inoculated through IV and oral routes of infection respectively. Isolation of NDV was positive from day 2 of PI and onward in all the groups with some minor variations in some cases. The CEF cell culture system was found more sensitive compared to avian embryo. Irrespective of routes of inoculation and age of birds, there was significant (p<0.01) increase in the mean HA titre of NDV with the progression of time. The highest HA titre of NDV was found in the brain tissue followed by lungs and kidney. Significantly (p<0.01) higher HA titre of NDV isolate was recorded in the birds of all the experimental groups inoculated through IV route. Following infection, the MDA titres decreased day by day in the birds with the increase of HA titres of NDV.
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