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Great Tits In Britain Showing Signs Of New Strain Of Avian Pox

November 23, 2012
Image Credit: Great tit with avian pox lesions. Photo: Vince Garvey

April Flowers for redOrbit.com – Your Universe Online

House sparrows, dunnocks, and wood pigeons, among other British bird species, have been known to carry avian pox. Vets and ornithologists are very concerned, however, about the emergence of a new strain of this viral disease in great tits.

According to wildlife veterinarian Dr Becki Lawson from the Zoological Society of London (ZSL), “Infection leads to warty, tumor-like growths on different parts of a bird’s body, particularly on the head around the eyes and beak. Although the disease can be relatively mild in some species, great tits suffer severe growths that can prevent them from feeding and increase their susceptibility to predation.”

Scientists from Oxford University performed a detailed monitoring in Wytham Woods for the last 50 years, which revealed that while a range of tits are susceptible to this new form of the disease, the great tits are by far the most susceptible. The results of this study were published in three separate papers in PLOS ONE.

“Although recovery from infection can occur, our results show that this new strain of avian poxvirus significantly reduces the survival of wild great tits and has particularly large effects on the survival of juvenile birds,” says Dr Shelly Lachish of the Edward Grey Institute at Oxford University.

Not every infected bird, dies, though. Some are able to recover.

“Based on the numbers of affected great tits that we have observed at Wytham Woods, our models do not predict that this new disease will cause an overall population decline of the species. However, pox-affected populations have lower yearly growth rates. Hence, they are likely to have greater difficulty in recovering from other environmental factors that might reduce their numbers,” Dr Lachish added.

Mike Toms, head of garden ecology at the British Trust for Ornithology (BTO), says that the disease spreads between birds and possibly contaminated surfaces. He recommends that people keep their bird feeders and feeding stations clean.

“As always, clean them on a regular basis: ideally every week or fortnight, by cleaning, rinsing and then air drying them,” Mr. Toms explained. The research team stresses, however, that the disease cannot pass from birds to humans.

Scientists from the ZSL and the Royal Society for the Protection of Birds (RSPB), with help from the public, have tracked the disease. It spread rapidly in five years from southeast England in 2006 to central England and into Wales currently. The early autumn months are when the annual seasonal peak of observed cases occur, but incidents continue to be reported at this time of year.

Any new sightings of birds showing symptoms should be reported to the RSPB Enquiries Unit. The research team of scientists, ornithologists and vets say that they would not have been able to study the emerging disease without the help of the public.

“We can’t do this kind of work, to find out about the health of British wildlife, unless the public take the time to keep their eyes peeled and report signs of sick and dead birds to us,” Dr. Lawson said.

From genetic analysis, the virus appears to be the same strain seen in Scandinavia and more recently in central Europe, so it seems unlikely that it originated in Great Britain. Data on bird movements from the BTO confirms that great tits rarely migrate outside the country, making it more likely that the virus spread to the UK through an infected vector, such as a mosquito.

Avian pox isn’t the only new disease devastating garden birds in the UK. A disease called trichomonosis, which is caused by a parasite, was discovered in the finch population in 2005.  Since that time, it has spread throughout the country and the Republic of Ireland.

Greenfinches have suffered the most, according to a Royal Society journal paper. About 1.5 million breeding birds have been lost.


Source: April Flowers for redOrbit.com - Your Universe Online



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