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Avian flu outbreak could be from improperly cultured VVND vaccine, suspect experts
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Saturday, 04 March, 2006, 08 : 00 AM [IST]
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Gireesh Babu, Chennai
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be the result of inoculating improperly cultured killed vaccine (inactivated viruses) in poultry, suspect avian disease experts.
Venkateshwara Hatcheries, one of the major hatcheries in India, had distributed killed vaccine for avian flu, labelled as Viscerotropic Velogenic Newcastle Disease (VVND), to the poultry farmers at Namakkal district of Tamil Nadu in 2003, sources from Avian Disease Laboratory, a unit under Tamil Nadu Veterinary and Animal Sciences University (TANUVAS), informed Food & Beverage News.
For diseases like avian flu, the killed vaccines are inoculated in the body for preparation of antibody against live viruses. The viruses are scientifically multiplied in the laboratory and inactivated by chemicals like formalin, Beta Propeo Lacton etc., to act as antigen. The killed vaccine will be received by the body as a foreign protein to produce antibody. Experts say that if the virus is not cultured properly in preparation of killed vaccine, the vaccine may generate live viruses in the new body to cause the original disease.
Even if the killed vaccine is present in the body, chances are high for the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) test to result positive for avian flu, as the test only show the presence of ribonucleic acid (RNA) of avian flu virus in the RNA of the bird, either the virus is active or not. Though the chicken is dead because of another disease, if the vaccine has been introduced in a period of 3 months, the RT-PCR test will show that the bird was affected by avian flu. Sources pointed that even if the mortality of flocks in Navapur was due to some disease like Raniket, as the company claims, the RT-PCR test will result positive in avian flu, if the killed vaccine was present in RNA.
The sources revealed that by 2003, Venkateshwara Hatcheries had distributed the vaccine in Tamil Nadu, in the label of VVND vaccine, by giving alerts of avian flu. The company used the situation of death of some fowls in Hyderabad, which was due to low pathogenic bird flu, by informing farmers that the disease is an indication of avian flu.
"Their tactics were not successful as we detected it and curbed the spread of the disease at the correct time," said a higher official. It is to be noted that the avain flu vaccines are not introduced in the country due to the fear that the disease may outbreak from the vaccine. The killed vaccines are used for the disease, as the live vaccine may result in major calamities. The killed vaccines, modified form of live viruses used instead of exact viruses, should be applied in the exact count, as the virus is unable to reproduce, which makes the vaccine more costly, added experts. Sources said that if the vaccine was inoculated in conceal, the fact should be brought out and should check which strain of virus was used in the vaccine. If the H5N1 virus is reported to be present in the vaccine, the disease is caused from the vaccine itself, added the sources.
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