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Sarcocystis rileyi in UK free-living wildfowl (Anatidae): surveillance, histopathology and first molecular characterisation
  1. Allan Muir1,2,3,
  2. Matthew Ellis4,
  3. Damer P Blake1,
  4. Julian Chantrey5,
  5. Emily A Strong2,
  6. Jonathon P Reeves2 and
  7. Ruth L Cromie2
  1. 1 Royal Veterinary College, Hatfield, Hertfordshire, UK
  2. 2 Wildfowl & Wetlands Trust, Slimbridge, Gloucestershire, UK
  3. 3 European Association of Zoos and Aquaria, Brussels, Etterbeek, Belgium
  4. 4 British Association for Shooting and Conservation, Rossett, Wrexham, UK
  5. 5 Department of Veterinary Pathology, Institute of Veterinary Science, University of Liverpool School of Life Sciences, Liverpool, Merseyside, UK
  1. Correspondence to Dr Ruth L Cromie, Wildfowl and Wetlands Trust, Slimbridge GL2 7BT, UK; ruth.cromie{at}


Background Reports from UK hunters of ‘rice grains’ in muscles of shot wildfowl (Anatidae) coincided temporally with the finding of sarcocystosis in a number of ducks found as part of the Wildfowl & Wetlands Trust long-term general surveillance of found dead waterbirds. Sarcocystis rileyi has also been relatively recently confirmed in wildfowl in north-eastern Europe.

Methods This study uses four approaches to investigate UK wildfowl sarcocystosis: first, through a hunter questionnaire that captured historical case data; secondly, through an online reporting system; thirdly, DNA sequencing to characterise UK cases; and fourthly, histological myopathy assessment of infected pectoral muscle.

Results Our questionnaire results suggest Sarcocystis infection is widely distributed throughout the UK and observed in 10 Anatidae species, reported cases increased since the 2010/2011 shooting season, with the online reporting system reflecting this increase. DNA sequencing (18S rRNA gene and internal transcribed spacer-1 region) of UK isolates confirmed S rileyi in the five dabbling duck host species tested and the associated histopathological myopathy is described.

Conclusion This work highlights an emerging issue to European wildfowl species and provides much opportunity for further research, including the impacts of S rileyi and the described myopathy on host health, fitness and survival.

  • Anatidae
  • emerging disease
  • rice breast disease
  • Sarcocystis
  • sarcocystosis
  • wildfowl
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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article.

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