Observations on the epidemiology of equine hydatidosis in Britain.

Of 1388 horses and ponies examined at two abattoirs in the north of England from November 1979 to September 1981, 123 (8.7 per cent) showed evidence of hydatid infection. Prevalence of infection was closely related to age, rising from nil in animals up to two years old to over 20 per cent of those over eight years. Full-mouthed horses and ponies had similar prevalence rates (14.9 and 14.5 per cent, respectively), but horses had nearly twice as many viable infections as ponies. The prevalence of infection varied with the region of origin of full-mouthed horses and ponies, with 18 per cent of those from mid and north west England infected, compared with approximately 12 per cent of horses and ponies from mid and south Wales, Yorkshire and Scotland. The highest rates of transmission of equine hydatidosis are believed to occur in south and east England. Infections were mainly hepatic, with only 11 per cent lung involvement. Sixty-six per cent of the infections were viable, 71 per cent of which had between one and 10 cysts. Multiocular cysts occurred in 26 per cent of infections.