A study of ovine gastro-intestinal strongylosis in a sheep flock on permanent pasture. II. Population dynamics of parasites on the pasture in 1977 and an epidemiological interpretation.
An overall study of gastro-intestinal parasitism was initiated in a flock of sheep in the Western central region of France (Limousin) comprising studies on the animals and on the pasture. Results of the study on animal parasitism and the possibilities of using pepsinogen blood level measurements were published previously (Hubert, Kerboeuf and Gruner, 1979). This report is concerned with the distribution of parasites on the pasture and a discussion on the epidemiology of these strongyles. The pasture was contamined throughout most the year, first by the ewes and then by the lambs from the second month onwards of their presence on the land. Maximum contamination occurred in Summer, but a precocious wave of Ostertagia and Haemonchus larvae on the pasture was responsible for the high incidence of O. circumcincta infections. Unfavourable summer weather depressed the development of eggs and two secondary waves of larvae at the end of August and the end of September brought about peaks of H. contortus and Trichostrongylus in lambs at the end of the summer. Far less Nematodirus were found than normal. In comparison with the weight gain of lambs treated regularly, untreated animals suffered a drop in their rate of growth from the beginning of July to the beginning of September corresponding to the ingestion of a great number of infective larvae. These preliminary results for the year 1977 show the necessity of continuing these observations for several years to enable the effect of preceding year's contamination to be properly assessed.
D000818:Animals; D004064:Digestive System / Q000469:parasitology*; D012621:Seasons; D012756:Sheep; D012757:Sheep Diseases / Q000469:parasitology*; D012987:Soil; D014251:Trichostrongyloidea / Q000254:growth & development*; D014252:Trichostrongyloidiasis / Q000469:parasitology / Q000662:veterinary*; D014887:Weather
D012987:Soil