Migration routes hold key to bird flu spread.
As part of a global consortium, Samantha Lycett investigated how a subtype of bird flu called H5N8 spread around the world following outbreaks in South Korea that began in early 2014. The virus spread to Japan, North America and Europe, causing outbreaks in birds there between autumn 2014 and spring 2015.
Scientists analysed migration patterns of wild birds infected with the H5N8 virus and compared the genetic code of viruses isolated from infected birds collected from 16 different countries.
Their findings reveal that H5N8 was most likely carried by long-distance flights of infected migrating wild birds from Asia to Europe and North America via their breeding grounds in the Arctic. In 2016/2017 H5N8 returned to Europe from Asia, again carried by wild birds.
“Bird flu is a major threat to the health and wellbeing of farmed chickens worldwide. Our findings show that with good surveillance, rapid data sharing and collaboration, we can track how infections spread across continents.”
Samantha Lycett, The Roslin Institute
Will the West Nile Virus reach the UK?
West Nile Virus (WNV) is a mosquito borne virus that circulates within avian reservoirs. WNV can spill over into humans and horses causing fever, acute morbidity and sometimes death.
Mosquitoes that are very capable of transmitting WNV were found in the UK in 2010. Outbreaks of WNV are common across Africa and Eastern Europe, and there have also been sporadic outbreaks in Spain and the Camargue Regional Park in France, but never in the UK. These areas all fall along a major bird migration route.
Scientists at Roslin and colleagues from across the UK estimated the risk of northward migrating passerine birds stopping in a WNV hotspot, becoming infected and carrying active infection into the country. They found that there is a small risk of migrating birds infected with WNV arriving in the UK if the disease is present in the Camargue during migratory season.
This risk is considerably greater if WNV were to circulate further north in France. The risk of the virus establishing itself in the UK and infecting humans will depend on a number of factors, in particular the time of year and the location in the UK that the birds arrive.
Why and how differently are birds migrating?
Many bird species are expanding their geographic distribution while others are contracting it to the point of extinction. What leads to this? Are there physiological and behavioural attributes of the birds leading a range shift?
In collaboration with scientists at UC Davis, USA, Simone Meddle, Professor of Behavioural Neuroendocrinology at the University of Edinburgh, has been looking into these questions in song birds that breed in the Arctic.
Changes in birds’ geographic distribution are caused by climate change, human disturbance and invasive species. Birds at the edge of the area where their population breed appear to be highly variable. These pioneering birds are physiologically and morphologically different to the population breeding within the historic range, which the team observed by comparing stress hormone profiles and response to stress in Gambel’s white-crowned sparrows.
The team also compared stress hormone profiles in snow buntings and Lapland longspurs on their arrival at their breeding grounds in Greenland and Alaska . It seems that the further north birds go, the higher their stress responses are, but these become virtually non-existent later on in the breeding season when the birds are moulting their feathers.
Flexibility in the stress response may be typical for birds nesting at the edges of their range and this ability will become more relevant as climate change leads to major shifts of breeding habitat and seasonal events for migratory birds.
For full article and references see The Roslin Institute
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