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Vaccination is only way to curb avian influenza, says Ceva expert

Jun 01, 2017 - Animal Pharm

By Malcolm Flanagan
Animal Pharm
June 1, 2017 

A leading animal health vaccination expert said there is no doubt about using vaccines to curb the global prevalence of avian influenza (AI).

Dr Yannick Gardin, Ceva Santé Animale director of science and innovation, told a recent poultry innovation summit in Bangkok the question "is not if countries use vaccines to control AI but when and how".

He said AI vaccination needs to be used as part of a global program, including biosecurity, detection of infection and destruction of disease positive flocks. He stressed new vaccines and novel vaccine technologies are available "that could surely help if trading and registration rules are updated".

Dr Gardin pointed out that AI is not the same as human influenza and vaccination needs to be highly specific to be effective. Put simply, efficacious protection against AI in poultry requires vaccines that are: cross protective; potentially multivalent; adaptable and updatable; and administrable in the hatchery.

"AI is a problem for the whole world not a few countries. At the same time AI is not just a problem for poultry flocks but also an issue for humans because of their zoonotic qualities. It needs to be eradicated and controlled.

"The main strains of AI are H5, H7 and H9. AI can be highly pathogenic or low pathogenic. However low pathogenic AI can mutate and become highly pathogenic. To complicate matters there are also sub-populations of highly pathogenic strains in low pathogenic AI," said Dr Gardin.

Dr Gardin said the reasons for vaccination, as opposed to relying on extensive biosecurity, are clear. He said they are: an increase in resistance; protection against clinical signs; reduction of shedding; decreased risk of transmission; slowing of the spread of AI; decreased circulation of deadly viruses; decreased possibility of mutations; and smaller zoonotic risk.

He noted the longer a country waits to use vaccination again AI the more complicated the disease scenario can become. He pointed to the situation in Taiwan during the first five months of 2015, when one AI strain initially appeared but by May of that year seven different ones were circulating.

"The efficacy of any AI vaccination strategy could be judged by the potential of the vaccine multiplied by the coverage of the target population," he said.

Migratory birds

Dr Gardin said AI started as a local problem in Asia when H5N1 was discovered in China in 1995. At first, it had a limited impact but overtime it became "a game changer for poultry flocks around the world".

Currently, 2,317 AI virus strains have been identified in 21,318 different wild birds. The spread of AI is seasonal with wild birds heading north in the spring in the Americas, whilst Asian migratory birds generally fly south in the fall, spreading the different AI strains.

Dr Gardin said the scale of poultry flock damage could be judged by the outbreaks in North America between 2014 to 2015, when US and Canadian animal health authorities had to cull 40 million poultry birds to curb the spread of the disease. During that time, outbreaks of H5N1, H5N2 and H5N8 were mainly reported in the US.

Last year, researchers in Scotland said much closer monitoring of the migration routes of wild birds could provide early warnings of potential deadly avian flu outbreaks. The recommendation follows research confirming migrating birds can help to spread deadly strains of avian flu around the world. The study was conducted by the Global Consortium for H5N8 and Related Influenza Viruses and involved scientists worldwide. Edinburgh University coordinated the research.

The study specifically investigated how a subtype of avian flu H5N8 moved around the world following outbreaks in South Korea that began in early 2014. The virus spread to Japan, North America, the Middle East and Europe, causing outbreaks in birds there between the fall of 2014 and spring 2015. Scientists analyzed migration patterns of wild birds that were found to be infected with the H5N8 virus. The team then compared the genetic code of viruses isolated from infected birds collected from 16 different countries.

Reprinted with permission of Animal Pharm News




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