Identification of Foot and Mouth Disease (FMD) Virus From Recently Outbreak Crossbred Cattle In Rajbari District of Bangladesh

Foot and mouth disease (FMD) is a devastating viral disease and endemic in nature in Bangladesh that causes huge economical losses. The present research work was aimed to determine the prevalence of FMD outbreaks and molecular detection of FMDV serotypes by uRT-PCR and gsRT-PCR test, respectively from crossbred cattle in the Rajbari district of Bangladesh during the period from January to June 2018. A total of 16 tongue epithelial samples were collected from clinically FMD suspected 2 to 3 years old crossbred cattle. 14 samples were positive by uRT-PCR. The detection rate of FMDV by uRT-PCR was 87.50%. Then uRT-PCR positive samples were serotype by gsRT-PCR. Serotype based prevalence of FMDV was 42.86%, 100%, 21.43% and 21.43% in O serotype, Asia-1 serotype, A serotype and mixed infection with Asia-1 and A, respectively. Considering the age, the prevalence of confirmed FMD outbreak was 42.86%, 35.71% and 21.43% at the age of 2, 2.5 and 3 years, respectively. Serotype A, O and Asia-1 is circulated in Rajbari district and required trivalent vaccine for prevention and control of FMD in that area. SAARC J. Agric., 19(1): 201-210 (2021)

Evolutionary Analysis of Structural Protein Gene VP1 of Foot-and-Mouth Disease Virus Serotype Asia 1

Foot-and-mouth disease virus (FMDV) serotype Asia 1 was mostly endemic in Asia and then was responsible for economically important viral disease of cloven-hoofed animals, but the study on its selection and evolutionary process is comparatively rare. In this study, we characterized 377 isolates from Asia collected up until 2012, including four vaccine strains. Maximum likelihood analysis suggested that the strains circulating in Asia were classified into 8 different groups (groups I–VIII) or were unclassified (viruses collected before 2000). On the basis of divergence time analyses, we infer that the TMRCA of Asia 1 virus existed approximately 86.29 years ago. The result suggested that the virus had a high mutation rate (5.745 × 10−3substitutions/site/year) in comparison to the other serotypes of FMDV VP1 gene. Furthermore, the structural protein VP1 was under lower selection pressure and the positive selection occurred at many sites, and four codons (positions 141, 146, 151, and 169) were located in known critical antigenic residues. The remaining sites were not located in known functional regions and were moderately conserved, and the reason for supporting all sites under positive selection remains to be elucidated because the power of these analyses was largely unknown.

Mapping of antigenic sites of foot-and-mouth disease virus serotype Asia 1 and relationships with sites described in other serotypes

Knowledge of the antigenic structure of foot-and-mouth disease virus (FMDV) has relevance in the development of diagnostic assays, in the evaluation of the antigenic variability and in the selection of appropriate vaccine strains. Antigenic sites have been investigated only in FMDVs of serotypes O, A and C, while it would be valuable to extend studies also to other serotypes. This paper reports the identification of antigenic sites involved in virus neutralization in the FMDV serotype Asia 1 by using a new panel of mAbs and their relation with sites described in other serotypes is discussed. Out of 24 mAbs raised against the FMDV serotype Asia 1, 10 neutralize viral infectivity and were used to select FMDV mutants resistant to neutralization. On the basis of their reactivity profile with virus mutants, the 10 neutralizing mAbs were clustered in four groups corresponding to four independent antigenic sites. By comparing the amino acid sequence of the parental virus and of virus mutants, the amino acids crucial for the four sites were mapped at the following positions: VP1 140–142, VP2 67–79, VP3 58/59 and VP3 218. Three of the four neutralizing sites identified and mapped on FMDV serotype Asia 1 correspond structurally and functionally to analogous sites described in FMDV serotypes O, A and C, enforcing the evidence that these are dominant antigenic sites in the FMDV structure. The fourth site, located at the C terminus of VP3, is a new independent site, described for the first time in FMDV.