Abstract
The present study was undertaken with the aim of determining the biological,
molecular and immunological nature of prevailing FMDV in Bangladesh. Based
on the objectives of this study vaccine strains of the viruses were selected from
the field isolates. Protective potentiality Of the experimentally prepared vaccine
was comparing with Other available vaccines used in the country. A total
Of 240 samples Of which vesicular fluid (V F) 20; tongue epithelium (TEp) 125;
gum tissue (GT) 40; tissue from inter-digital spaces of foot (TIDF) 40 and teat
crust (TC) 15 were collected from the suspected FMD affected cattle Of 40
different districts Of Bangladesh during January 1998 to May 2000. All the field
samples were primarily passaged into three different indicator host systems
(unweaned mice, guineapig and BHK-21 cell line) to study the biological nature
of the field viruses. Based on the Characteristic symptoms and lesions developed
in the indicator host systems the viruses were isolated. The isolated viruses were
identified by ELISA using panel Of monoclonal antibodies (#75, #99,3H3, 4B 12,
15F7 and 8E9) against type 01, A and Asia-I ty'1B of FMDV. Serological results
of the present study that the isolates of the year from January 1998 to
March 1999 were positive for type O and that of October 1999 to May 2000 were
type A FMDV. Molecular techniques RT-PCR, nucleotide (nt) and amino acid
(aa) sequences of the viral VPI and their alignments were used for the
detection of viruses and determination Of variation of the genome of
FMDV isolates of Bangladesh. Results of alignment of nt/aa sequences Of the
isolates (type A & O) from 1998-2000 revealed 3.5-5 % variation in the genome
of the same types of FMD viruses Of previous years Of Bangladesh and Other
countries of the world. Neutralizing and precipitating antibody level of sera Of
vaccinated animals (calves, mice and guineapigs) were measured to comparing
immune response of the three vaccines by mSNT, PRNA and IDT. Protective
EX)tentiality of the three FMD vaccines was also determined by challenging the
vaccinated animals with homologous viruses at a dose of 100, 1, 000 and 10,000
TCID50 at day15 and 30 DPV in mice, guineapigs and calves respectively.
Animals those were vaccinated with the BAU-FMD and Hoechst-FMD vaccines
withstood 100% protection in virulent challenge whereas the animals those were
vaccinated with the DLS-FMD vaccine showed variable results (50% calves and
100% mice and guineapigs vyotected) in the virulent challenge. From the above
findings of this study it may be concluded that to control the frequent outbreaks
of FMD in the livestock population of Bangladesh, inactivated bi or prevailing field isolates should be used for better protection.