Mt Islam

Molecular characterization of two Bangladeshi infectious bursal disease virus isolates using the hypervariable sequence of VP2 as a genetic marker

Two Bangladeshi infectious bursal disease virus (IBDV) isolates collected in 2007, termed GB1 and GB3, were subjected to comparative sequencing and phylogenetic analyses. Sequence analysis of a 474-bp hypervariable region in the VP2 gene revealed that among four major amino acid substitutions observed in the strains, two were unique to GB1 and GB3 (Ser217Leu and Ala270Thr) while one substitution was only found in GB1 (Asn299Ser). Among IBDVs from Bangladesh including GB1 and GB3, the rate of identity and homology was around 97~99%. The amino acid sequences of GB1 and GB3 differ from those of previous Bangladeshi IBDV isolates and contain amino acid substitutions Pro222Ala and Asn299Ser (in GB3 only). Phylogenetic analysis revealed that GB1 and GB3 are grouped with other very virulent IBDVs of European and American origin in contrast to two previously isolated Bangladeshi IBDV strains (GenBank accession Nos. AF362776 and AF260317), which belong to the Asian group. It was concluded that GB1 and GB3 belong to a very virulent group of IBDVs. However, amino acid sequences of GB1 and GB3 differ from those of the other Bangladeshi IBDVs by one or two amino acids encoded in the hypervariable region of the VP2 gene.

STANDARDIZATION OF EFFECTIVE DOSE OF FOWL CHOLERA VACCINE IN PIGEON IN BANGLADESH

An experiment was conducted to determine the effective dose of formalin killed (FK) fowl cholera (FC) vaccines prepared with virulent avian Pasteurella multocida (PM 38) serotype 1 (X-73) collected from the laboratory of the Department of Microbiology and Hygiene, BAU, Mymensingh. To determine the effective dose of vaccine, 7 weeks old 30 pigeons were immunized and each group consists of 5 birds. The groups are represented by A, B, C, D, E and F. The birds belonging to groups (A-E) were vaccinated with different doses of vaccine, after two weeks of first, second immunization and challenge experiment, blood was collected from all vaccinated birds, and serum was analyzed to determine antibody titer against P. multocida by passive hemagglutination test (PHA). The PHA titer after two weeks of first vaccination were 16±3.92, 17.6±3.92, 25.6±3.92, 32±8.76, 35.2±7.84 of group A,B,C,D and E, respectively at the dose of 0.2ml (0.26×108 CFU)/birds, 0.4ml (0.5×108 CFU)/birds, 0.8 ml (1.04×108 CFU)/birds, 1ml (1.3×108 CFU)/birds, respectively. The PHA titer of prevaccination and control birds was <4. The PHA titer after 2 weeks of second vaccination or boostering were 32±8.76, 35.2±7.84, 44.8±7.84, 57.6±18.66, 70.4±15.68, of group A,B,C,D and E, respectively. After 2 weeks of challenge infection, the mean PHA titer were 44.8±7.84, 51.2±7.84, 70.4±15.68, 102.4±15.68 and 140.8±31.34 of group A,B,C,D and E, respectively. In this experiment, the antibody titer of the vaccinated pigeons with 0.4, 0.6, 0.8 and 1ml per bird via intramuscular route were higher than that of the pigeons vaccinated with 0.4ml/bird, 0.6ml/bird, 0.8ml/bird and 1ml/bird were satisfactory in terms of protective potential against P. multocida. For prevention and control of avian pasteurellosis 0.4ml to o.6ml (0.52×108 CFU to 0.78×108 CFU)/birds of vaccine may be used instead of 1ml (1.3×108 CFU)/birds for better immunization of pigeon against fowl cholera infection.