In Bangladesh, Ind-2001d, Ind-2001BD1 and Ind-2001BD2 under the Ind-2001 lineage of ME-SA topotype were found to circulate 3. The high mutation rate of the viral genome, lack of proofreading activity of the RNA polymerase and the quasi-species nature of the virus are responsible for the emergence of genetically and antigenically diverse strains of FMDV 19, 20. Recently, a distinct novel lineage, SA-2018 under ME-SA topotype was reported from India in 2018 19. Ind-2001 lineage is diversified into five sublineages: Ind-2001a, b, c, d, and e 3, 6, 18. These lineages (Pak-98 and Srl-97) were endemic and were not detected outside the respective countries 16, 17. But two other endemic lineages, Pak-98 from Pakistan and Srl-97 from Sri Lanka were also documented. So far, there are four established lineages under the ME-SA topotype, namely Ind-2001, Ind-2011, PanAsia and PanAsia-2 3, 14, 15. Serotype O can be subdivided into 11 topotypes but only the Middle East-South Asia (ME-SA) topotype is found in Bangladesh. Among them, serotype O is the most predominant one and was responsible for 82% of the outbreaks in Bangladesh during 2012–2016 3. In Bangladesh, serotype O, A and Asia1 were found to circulate among the 7 distinct serotypes of FMDV (Euro-Asiatic serotypes A, O, C, and Asia1 and Southern African Territories serotypes SAT1, SAT2, and SAT3) 2, 11, 12, 13. VP1 sequence data analyses are widely utilized for molecular characterization of field FMDV strains and revealing evolutionary divergence among individual virus strains 3, 6, 7, 8, 9, 10. Among the capsid proteins, VP1 capsid protein possesses three out of five major neutralizing antigenic sites: antigenic sites 1, 3, and 5 5. The FMDV possesses a positive-sense single-stranded RNA genome of about 8.5 kb surrounded by an icosahedral capsid with 60 copies of each of four structural proteins VP1, VP2, VP3, and VP4 4. The causative agent is a notorious virus called Foot-and-Mouth Disease Virus (FMDV) which belongs to the genus Aphthovirus and the family Picornaviridae 2, 3, 4. FMD is widespread in many areas around the globe, especially in Africa and Asia including Bangladesh. This is the first report on the emergence of the SA-2018 lineage of ME-SA topotype of FMDV serotype O in Bangladesh, as well as a possible mutational trend towards the emergence of a distinct sublineage under SA-2018 lineage, which calls for in-depth genome-wide analysis and monitoring of the FMD situation in the country to implement a strategic vaccination and effective FMD control program.įoot-and-Mouth Disease (FMD) is an acute and highly contagious disease that affects cloven-hoofed animals like cattle, pigs, sheep, goats, and water buffalo 1. Analysis of the amino acid sequence revealed several changes in the G-H loop, B-C loop and C-terminal region of VP1, revealing a 12–13% divergence from the existing vaccine strains and a 95% VP1 protein homology, with most of the mutations potentially considerable as vaccine escape mutations, evidenced by three-dimensional structural analysis. The mutational spectrum, evolutionary divergence analysis and multidimensional plotting confirmed the isolates collected from Mymensingh districts, designated as MYMBD21 as a novel sublineage under the SA-2018 lineage. This study detected the first emergence of the SA-2018 lineage in Bangladesh along with the predominance of Ind-2001e (or Ind-2001BD1) sublineage of ME-SA topotype under serotype O during 2019–21. The current study was conducted in nine districts of Bangladesh during 2019–21 to characterize the circulating FMDV strains based on the VP1 sequence analysis, the major antigenic recognition site providing serotype specificity and high variability of FMDV. The management and prevention of FMD are severely impacted by the high mutation rate and subsequent frequent generation of newer genotypes of the causative agent, Foot-and-Mouth Disease Virus (FMDV). Foot-and-Mouth Disease (FMD) hinders the growth of the livestock industry in endemic countries like Bangladesh.
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