| UPLANDS - CRYPTOSPORIDIOSIS IN RED GROUSE
Respiratory cryptosporidiosis in red grouse Infection by cryptosporidiosis has impacted grouse, with infected birds having 51% lower survival and rearing 43% fewer chicks relative to healthy birds on the same moor. © Laurie Campbell
BACKGROUND Infection by Cryptosporidium baileyi, a parasitic protozoan, causes respiratory cryptosporidiosis in red grouse. It was first diagnosed in 2010 and has spread with infection rates higher in young birds. Understanding underlying causes of disease emergence and routes of infection transmission are fundamental to its subsequent control.
66 | GAME & WILDLIFE REVIEW 2019
Cryptosporidia are protozoan parasites that are widespread among vertebrates, causing gastrointestinal diseases in mammals and reptiles and enteric, renal and respiratory diseases in birds. Two species, Cryptosporidium baileyi and C. galli, are restricted to birds. In most cases, pathogenic infection has been restricted to domestic poultry, captive-reared gamebirds or other birds kept in captive collections. In 2010, red grouse in northern England were clinically diagnosed with respiratory cryptosporidiosis following infection from C. baileyi. Within three years of the first outbreak, our questionnaire survey to gamekeepers showed that signs of infection were detected from grouse on half of 150 grouse moors in northern England. Reported prevalence among shot birds, confirmed in the field by catching at night and visual screening, has been low, typically averaging 4% of birds. Infection by cryptosporidiosis has impacted grouse, with infected birds having 51% lower survival and rearing 43% fewer chicks relative to healthy birds on the same moor. Thus, should prevalence increase, respiratory cryptosporidiosis could markedly impact upon shooting bags and grouse moor economics. To monitor disease prevalence, we examined 45,914 red grouse shot between 2013-18. Birds were sampled from 30 beats of 10 driven grouse moors in northern England. Grouse were aged, sexed and visually screened for signs of infection. Prevalence varied with age, being twice as high in juveniles (4.5%) as in adults (2.4%). It also varied nine-fold between moors from 1.0 to 8.6% and three-fold between years (see Table 1). Patterns of infection among grouse age groups and across years were consistent across study moors.
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