Avian pox on the rise in Britain

Photo by Luc Viatour

Alarm bells have been raised in Britain over the health of the country’s great tits, following a confirmed case of avian pox virus in a great tit population in Oxfordshire. Although the disease has previously been found in house sparrows and wood pigeons in Kent, Sussex and Surrey, the spread to great tit populations is of great concern to researchers, since tits are among a number of wild bird species that are known to be less resilient to the disease.

The first confirmed case of AVP in a British great tit occurred in 2006, but the latest incident was found in a great tit population that has been continuously monitored by scientists from the University of Oxford, and the Zoological Society of London, since 1947.

When the presence of AVP was confirmed Professor Ben Sheldon from the University of Oxford’s Edward Grey Institute said researchers were: “using our detailed observations to try to understand how this new form of pox affects survival and reproductive success.”

Historically AVP is known to affect bird species worldwide, but it is more commonly found throughout temperate regions. Transmission occurs either through mosquito or other insect bites, or by direct contact with infected birds. Infection is also possible via contaminated communal food and water sources.

Symptoms include weakness, emaciation, soiled facial feathers, reduced egg reduction, and the growth of warty lesions on unfeathered areas of birds’ bodies, particularly the eyes and beaks.

AVP is a slow-developing disease that ultimately affects the birds’ ability to see and fly, causing them to gradually weaken until they become more susceptible to predators. AVP is also known to be highly resistent to drying and can persist in the environment for months, or even years, in the dried scabs from infected birds. Some species are also more sensitive to the disease than others according to ZSL’s wildlife vet Becki Lawson.

“When we see this infection in great tits, the lesions can be a lot more severe than in other species. They can be very large, most common on the head, but they can occur on other areas of the body. It seems not uncommon for multiple birds to be affected in one incident,” she said.

Lawson is currently working with other scientists to isolate and sequence AVP genes to identify if the latest outbreak is the same strain that affects birds in central Europe. She has also led the call for public support to assist researchers track the disease, and determine its wider impact on Britain’s birds,

“We now believe avian pox has spread as far north as Staffordshire. Public reports of sick birds are essential in helping us to track the disease and determine the wider impact it’s having on our garden birds,” she said.

The public is being encouraged to disinfect bird tables and feeders and to report any sightings of birds that may be infected to the Royal Society of Birds.

“We can’t give medicine to free-ranging birds, but we recommend people give particular attention to good hygiene at feeding stations to prevent the cycle of transmission of any particular disease agent that could occur there,” said Lawson.

There is no known treatment for avian pox in wild birds, and no evidence that AVP can infect humans.
Anne Layton-Bennett

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