EPIDEMIOLOGIC SURVEY TO BOT INFECTION IN HORSES AT NECROPSY IN NORMANDY FROM APRIL-1990 TO MARCH-1992

Stomachs of 384 horses were examined at necropsy in a two-year period and 130 of them had bot larvae. The prevalence was 33.85 p.cent and re ached 38.76 p.cent when the data for the months of july, august and se ptember were excluded. The females were more frequently infected than the males, respectively 40.26 p.cent and 24.60 p.cent. Prevalence of b ot infection showed seasonal variations: the highest prevalence occure d in fall (54.08 p.cent) and the least in summer (21.29 p.cent). The c ommonest species of Gasterophilus sp. infecting horses in Normandy wer e : G. intestinalis 33 p.cent, G. nasalis 13 p.cent and G. haemorrhoid alis 1.82 p.cent. The 3 species of bot had same predilection sites of attachment : the squamous mucosa close to the margo plicatus and the s accus caecus. The majority of horses (66.77 p.cent) had less than 50 b ot larvae and only 19.35 p.cent harboured more than 100 parasites.