Vaccines combine to produce deadly virus

Vaccines combine to produce deadly virus

Vaccines aren't supposed to cause disease. But that appears to be what's happening on Australian farms.

Scientists have found that two virus strains used to vaccinate chickens there may have recombined to form a virus that is sickening and killing the animals.

"This shows that recombination of such strains can happen and people need to think about it," said Glenn Browning, a veterinary microbiologist at the University of Melbourne, Parkville, in Australia and one of the co-authors on the paper.

Chickens worldwide are susceptible to a group of herpesviruses called ILTV, which target their upper respiratory tract. The resulting disease, known as infectious laryngotracheitis (ILTV), reduces egg production and can kill up to one-fifth of those infected.

"The birds effectively choke to death on blood and mucus," said Browning. The disease is not known to infect any other animals other than chicken and chicken-like birds.

To combat ILTV, farmers vaccinate their chickens with attenuated herpesviruses that can still infect and replicate but do not lead to disease.

Australia has used two vaccines, which are produced by Pfizer and called SA2 and A20. In 2006, however, the country purchased a new vaccine from European company Intervet called Serva.

Two years later, new strains of ILTV, called class 8 and 9, appeared. They are just as deadly as other strains. "But they seem to be dominating over the strains that were reported prior to 2007," said Browning.

Because the new strains appeared shortly after the European vaccine was introduced, scientists thought that the new vaccine strain might have reverted back to a disease-causing form.

But when the researchers sequenced the genomes of the two new strains and the three vaccine strains, they found that the new viruses were actually stitched together from the European and Australian vaccines. Although it was not clear what mutations kept the vaccine strains from causing disease in the first place, they were probably lost when the viruses recombined, said Browning, whose team reports its findings online in Science.

"This is quite possible but a bit surprising since it would imply that both vaccines have gone into the same animal, which would be required for recombination to occur," Paul Farrell, a virologist at Imperial College London, wrote in a statement released by the Science Media Centre.

Farmers do not deliberately vaccinate with both vaccines, Browning agreed. But the SA2 strain might have spread into an unvaccinated population that was later vaccinated with the Serva strain, he suggested.

The data for the recombination is "convincing," said Walter Fuchs, who heads the National Reference Laboratory for Infectious Laryngotracheitis of Poultry on the island of Riems in Germany.

The combination of vaccine strains to form a new virus is "a problem that needs to be taken seriously," added Thomas Mettenleiter, head of the Federal Research Institute for Animal Health also on Riems.

Only well-characterised live vaccines, rendered harmless by mutations in the same or overlapping regions, should be used in order to minimise the risk of recombination to a new virulent strain, he argued.

Live-attenuated vaccines are also used in humans, but a lot less than in poultry, and their sequence is usually known. "This is not a panic-button on vaccines," said Browning.

And Farrell stressed vaccines had been one of the great success stories of medicine.

"The type of important technicality raised in this article should not be allowed to detract from the enormous health benefit generally provided by vaccines," he wrote.

Science Now

Views: 69

Comment

You need to be a member of 12160 Social Network to add comments!

Join 12160 Social Network

"Destroying the New World Order"

TOP CONTENT THIS WEEK

THANK YOU FOR SUPPORTING THE SITE!

mobile page

12160.info/m

12160 Administrators

 

Latest Activity

Doc Vega posted a blog post

In Memory of Those Who Served

 Bullets flew and ricochetedI was on that hill todayMy Company commander got blown awayI was on…See More
15 hours ago
Doc Vega posted blog posts
Tuesday
Doc Vega commented on Doc Vega's blog post Plausible Explanation Behind Recent Cryptid Sightings in the Wild!
"cheeki kea I was wrong Emperor Penguins are big and powerful but still alive but this,  A size…"
Tuesday
Doc Vega commented on Doc Vega's blog post Plausible Explanation Behind Recent Cryptid Sightings in the Wild!
"Cheeki kea here's another that they say there have been modern sightings of!  The name of…"
Tuesday
Doc Vega commented on Doc Vega's blog post Plausible Explanation Behind Recent Cryptid Sightings in the Wild!
"cheeki kea, did you ever hear of the giant Imperial Penguins? They were about 6 feet tall and could…"
Tuesday
Doc Vega commented on Doc Vega's blog post Plausible Explanation Behind Recent Cryptid Sightings in the Wild!
"cheeki kea I do not think these giant two legged birds would need to have a bad attitude as long as…"
Tuesday
Olivia Brooks updated their profile
Tuesday
John Miller was featured
Tuesday
tjdavis's 2 blog posts were featured
Tuesday
Zfort Group's blog post was featured
Tuesday
Doc Vega's 6 blog posts were featured
Tuesday
Burbia commented on tjdavis's video
Thumbnail

“What’s His Motive?” - Inside The Mind of George Soros

"Trump calls for George Soros and son to face federal…"
Tuesday
Burbia commented on tjdavis's photo
Tuesday
Profile IconSeeta Sathe and Olivia Brooks joined 12160 Social Network
Tuesday
tjdavis posted a video

Mossad, Terrifying CIA Technology, Blackwater & The Most Secret CIA Unit | John Kiriakou

John Kiriakou served 15 years in the CIA as a Case Officer (Spy) and as CIA's Head of Counterterrorism Operations in Pakistan where he lead the raid that cap...
Monday
tjdavis posted a photo
Monday
tjdavis posted a video

A Critique of the Tavistock Institute - The Mother Of All Conspiracy Theories

An examination of the Tavistock Institute, a theory which seeks to explain how Western societies have been brainwashed by a cabal of social scientists and th...
Sunday
tjdavis posted a video

“What’s His Motive?” - Inside The Mind of George Soros

In this short clip, Patrick Bet-David, Sebastian Gorka Adam Sosnick, and Tom Ellsworth George Soros and what motivates him to do the things he does. FaceTime...
Aug 27
Doc Vega posted blog posts
Aug 27
cheeki kea favorited Bob of the Family Renner's photo
Aug 26

© 2025   Created by truth.   Powered by

Badges  |  Report an Issue  |  Terms of Service

content and site copyright 12160.info 2007-2019 - all rights reserved. unless otherwise noted