Veterinary Services

Spironucleosis in Game Birds in Great Britain 1996 to 2008

Spironucleosis (formerly referred to as hexamitiasis or hexamitosis) is a common cause of weight loss, diarrhoea and death in reared and released pheasants and red-legged partridges. Previously prevention and treatment of this condition relied on the use of in-feed and in-water medication containing dimetridazole. In recent years these products have not been available to the game bird industry. Instead, control is based on good management and hygiene practices. Treatment of affected groups with tetracycline antibiotics in the drinking water appears to be beneficial.  Spironucleus meleagridis is a motile protozoan organism found mostly in the small intestine. Two other motile protozoa, associated with disease in game birds, Trichomonas phasiani and Histomonas meleagridis, are found in the caeca.

Figure 5 (see top right-hand side) shows the number of batches of game birds submitted to SAC and the Veterinary Laboratories Agency (VLA) in which infection with motile protozoa (excluding trichomonosis and histomonosis) was diagnosed. A cyclical pattern can be seen between 1996 and 2008, apparently unrelated to the withdrawal of dimetridazole from 2002. However when the diagnoses are expressed as a percentage of the number of game bird submissions received (figure 6 - see top right-hand side), the percentage of diagnostic submissions in which spironucleosis was confirmed has increased steadily since 2005. Disease was especially common in 2007 largely due to an increase in cases in September 2007. The reason for this increase is unclear, but August 2007 was cold in many areas of Great Britain and possibly adversely affected the health of the birds immediately prior to September 2007.

These figures suggest that spironucleosis will continue to be a problem for game birds in the years to come, and that the control of this disease should form a major part of health plans prepared by game bird rearers and their veterinary advisers.

Wild birds

Six male buzzards (Buteo buteo), found dead or dying in six different locations were submitted. One bird had evidence of trauma and secondary cellulitis. The remaining five birds were all in thin condition with an absence of food in the digestive tract. Dark red or black material was present in the proventriculus, gizzard and intestines, typical of birds that have died from starvation. Some of the birds had concurrent helminth burdens, including hairworms (Eucoleus species) causing a necrotic glossitis, Cyathostoma species in the bony orbits, large roundworms (Porrocaecum species) in the duodenum and small intestine, and unidentified intestinal tapeworms. Reports were received of other dead buzzards in the west and southwest of Scotland, initially prompting fears by those finding the birds of possible poisoning. The cause of starvation in the buzzards most likely reflected the increased numbers in recent years coupled with very cold weather in December. Prolonged frosts result in limited access to earthworms, an important aspect of the diet of buzzards. Similarly, vole numbers have reduced, and carrion may have been unavailable due to freezing conditions. The deaths probably represented “natural” limitations on buzzard numbers. Starvation and parasitism (thickening of the oesophagus caused by hairworms) was also found in a thin kestrel (Falco tinnunculus).