Vaccination helps against bird flu, don’t kill birds


This July 2015 video from the USA says about itself:

Despite some disagreement about whether to approve and deploy a vaccine against H5N2 bird flu, the latest iteration of such a drug appears to be remarkably effective.

US Agriculture Secretary Tom Vilsack told the House Agriculture Committee that researchers had developed a vaccine that was 100 percent effective against H5N2 in chickens, with testing in turkeys currently ongoing, reports CBS News. If approved, the vaccine could be produced and rapidly used in the event of further outbreak.

From this blog, 20 December 2014:

But now also a chicken business in Ter Aar [in the Netherlands] turns out to be infected [by bird flu]. Again, tens of thousands of chickens will be killed. Is that really the best way to fight the disease?

Just this week it was announced that vaccination is possible. Dutch researchers are the first scientists who have succeeded in developing a vaccine that can be administered on a large scale. One of the researchers, Professor of Pharmaceutical Technology and Biopharmaceutics Erik Frijlink, explains that vaccination is a better way to prevent outbreaks of bird flu.

The vaccine has been developed on the basis of H5N1, but the technique is also applicable for H5N8, the ‘Hekendorp‘ virus.

The image shows a graphical abstract: H7N9 highly pathogenic avian influenza viruses emerged in China in 2017, prompting vaccination in poultry. Shi et al. examine H7N9 viruses across China before and after vaccination, revealing rapid evolution into subtypes and genotypes. Although vaccination reduced infections, some H7N9 and H7N2 viruses exhibit heightened virulence and expansion to ducks. Credit: Chen et al. / Cell Host & Microbe 2018

From ScienceDaily:

New bird flu viruses in ducks after vaccines largely prevented H7N9 in chickens

September 27, 2018

In response to bird flu pandemics starting in 2013, officials in China introduced a new vaccine for chickens in September 2017. Recent findings suggest that the vaccine largely worked but detected two new genetic variations of the H7N9 and H7N2 subtypes in unvaccinated ducks. These findings will be published in the journal Cell Host & Microbe on September 27.

“It surprised me that the novel, highly pathogenic subtypes had been generated in and adapted so well to ducks, because the original highly pathogenic form of H7N9 has very limited capacity to replicate in ducks,” says Hualan Chen, a senior author on the paper and an animal virologist at the Harbin Veterinary Research Institute.

Chen’s team collected over 37,928 chickens and 15,956 duck genetic samples 8 months before and 5 months after the vaccine’s introduction. They isolated 304 H7N9 viruses before the vaccine’s release, and only 17 H7N9 viruses and one H7N2 virus after.

“Our data show that vaccination of chickens successfully prevented the spread of the H7N9 virus in China,” says Chen. “The fact that human infection has not been detected since February 2018 indicates that consumers of poultry have also been well-protected from H7N9 infection.”

The bird flu virus replicates in host cells and often mutates and reassorts over time. When Chen’s team looked closely at the genetic types of the disease-causing strains in ducks, they found that an H7N2 and an H7N9 virus had picked up certain gene segments from other duck influenza viruses, improving their ability to infect ducks.

“Influenza viruses mutate as long as they replicate, but it’s very difficult to predict when the H7N9 virus will obtain a particular harmful mutation,” says Chen. “It is possible that the virus may adapt in other species in the future if it cannot be eliminated soon.”

China produces roughly three billion ducks per year, which is not to the scale of chicken production. To prevent further human infection, Chen and her team believe that the virus should be eliminated in ducks as soon as possible.

“Fortunately, our study indicates that the current vaccine will work well in ducks, so we do not need to develop a new one,” says Chen. “We suggest applying the H7 vaccine in ducks immediately.”

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