Pathotyping of a recently isolated genotype VII Newcastle disease virus by mean death time and intracerebral pathogenicity index

Tan, Ee Ling (2022) Pathotyping of a recently isolated genotype VII Newcastle disease virus by mean death time and intracerebral pathogenicity index. [Project Paper] (Submitted)

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Abstract

Newcastle Disease (ND) is a devastating poultry disease that remains persistent worldwide despite intense vaccination programs. NDV can be classified into 3 pathotypes: velogenic, mesogenic, and lentogenic. For the past 2 years, commercial farms in Malaysia have experienced major genotype VII ND outbreaks. Characterisation of recently isolated field virulent ND is necessary for developing challenge viruses in vaccine efficacy studies. In a previous study, genotype VII NDV strain UPM008/2021 was isolated in embryonated specific-pathogen-free (SPF) chicken eggs and characterised by fusion (F) gene sequencing. A study was undertaken to determine the pathotype of the isolated NDV via mean death time (MDT) and intracerebral pathogenicity index (ICPI). MDT was conducted to determine the average time for the minimum lethal dose (MLD) to cause 100% embryonic mortality. NDV isolate is classified as velogenic, mesogenic, and lentogenic according to MDT at <60 hours, 60-90 hours, and >90 hours, respectively. ICPI was conducted to determine the average score per bird for each observation for 8 days, based on scoring ‘0’-normal, ‘1’-sick, and ‘2’-dead. Velogenic strains produced ICPI near 2.0, while lentogenic strains produced ICPI near or equal to 0. In this study, the genotype VII NDV strain UPM008/2021 is classified as a velogenic NDV with MDT (59.2 hours) and ICPI (1.75), confirming a previous study that indicated the virus is a velogenic strain based on F gene sequencing. These findings emphasise the importance of virus pathotyping in distinguishing between virus strains, confirming NDV diagnosis, and allowing the use of the virus as a challenge virus in vaccine efficacy studies.

Item Type:	Project Paper
Faculty:	Faculty of Veterinary Medicine
Depositing User:	Ms. Nordeena Abdul Aziz
Date Deposited:	29 Feb 2024 07:22
Last Modified:	29 Feb 2024 07:22
URI:	http://psaspb.upm.edu.my/id/eprint/1651

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