AN EPIDEMIOLOGIC-STUDY OF GASTROINTESTINAL PARASITISM IN DAIRY SHEEP FLOCKS IN LEON (NW SPAIN)

The present study was carried out to contribute to the knowledge of th e epidemiology of gastrointestinal nematode infections in milking ewes raised under semi-intensive management conditions in Leon province (N W Spain). A total of 779 faecal samples from 368 dairy sheep flocks of Churra and Churra X Assaf breeds, were analyzed during April 1991-Mar ch 1993 for gastrointestinal nematodes. These flocks came from 6 areas located in the south-east of Leon province. From the total faecal sam ples studied, 87.9% were positive to gastrointestinal nematodes, with a mean egg counts of 134.3 eggs per gram (epg), and a range of 0 to 20 50 epg. No overall significant differences were found between differen t areas regarding to the prevalence of infected flocks. Data showed th at faecal egg output was positive all year around but showed a two-pea k pattern. The first and higher significant peak appeared during late winter to early spring (March) and the second maximum in mid summer (A ugust). A relationship was found between climate conditions and the pa ttern of faecal egg output. The prevalence of infection showed a signi ficant seasonal difference (chi-square = 7.93; P = 0.047). Ln conclusi on, environmental factors affected the prevalence and intensity of gas trointestinal infection under semi-intensive management conditions. Th is study states the present knowledge of the epidemiology of gastroint estinal parasitism in sheep in Leon and may lead to improve applicatio n of existing control strategies. (C) 1998 Elsevier Science B.V.