Spatio-temporal dynamics and aetiology of proliferative leg skin lesions in wild British finches

Chaffinch by Jill Pakenham

Author(s): Lawson, B., Robinson, R.A., Rodriquez-Ramos Fernandez, J., John, S.K., Benitez, L., Tolf, C., Risely, K., Toms, M., Cunnigham, A.A. & William, R.A.J

Published: 1 October 2018

Journal: Scientific Reports Volume: 8

Article No.: 14670

Digital Identifier No. (DOI): 10.1038/s41598-018-32255-y

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Leg lesions, more commonly known as ‘scaly leg’ or ‘tassel foot’ are growths on the legs of feet of finches. A study from the Zoological Society of London in collaboration with BTO, the Complutense University of Madrid and Linnaeus University, explores the causes, seasonality and distribution of one of the most notable diseases in wild birds in Britain.

Leg lesions are one of the most commonly seen signs of ill health in British birds. Results from post-mortems on over a thousand finches have found that these leg lesions have two causes; a virus (Fringilla coelebs papillomavirus) and mites (Cnemidocoptes). The most frequently affected birds are Chaffinches but leg lesions have also been documented in other finch species.

Weekly reports from BTO Garden BirdWatchers, as well as ad hoc sightings of disease from members of the public to Garden Wildlife Health, show that leg lesions in finches are widespread across the UK. However, reports of leg lesions increase during the winter period between November- March, at a time when we see an influx of Chaffinches from the continent, joining our breeding birds. The increase in migratory finches at this time might help to explain the increase in disease reporting rate in the winter months.

We know that leg lesions, whilst distressing to see, often do not impede the birds and most of the time they behave normally, but in severe cases birds can become lame and will be increasingly vulnerable to predation. Currently there is no evidence that leg lesions pose a threat to conservation of wild finches. 

You can help reduce the spread of the disease in your garden by following good hygiene measures when feeding garden birds, such as regularly cleaning your feeders.  For more information on how to prevent disease and to report disease in your garden see the Garden Wildlife Health website.

Abstract

Proliferative leg skin lesions have been described in wild finches in Europe although there have been no large-scale studies of their aetiology or epizootiology to date. Firstly, disease surveillance, utilising public reporting of observations of live wild finches was conducted in Great Britain (GB) and showed proliferative leg skin lesions in Chaffinches (Fringilla coelebs) to be widespread. Seasonal variation was observed, with a peak during the winter months. Secondly, pathological investigations were performed on a sample of 39 Chaffinches, four Bullfinches (Pyrrhula pyrrhula), one Greenfinch (Chloris chloris) and one Goldfinch (Carduelis carduelis) with proliferative leg skin lesions and detected Cnemidocoptes sp. mites in 91% (41/45) of affected finches and from all species examined. Fringilla coelebs papillomavirus (FcPV1) PCR was positive in 74% (23/31) of birds tested: a 394 base pair sequence was derived from 20 of these birds, from all examined species, with 100% identity to reference genomes. Both mites and FcPV1 DNA were detected in 71% (20/28) of birds tested for both pathogens. Histopathological examination of lesions did not discriminate the relative importance of mite or FcPV1 infection as their cause. Development of techniques to localise FcPV1 within lesions is required to elucidate the pathological significance of FcPV1 DNA detection.
Staff Author(s)

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