Preliminary investigation on the seasonal occurrence of ovine parasites around sheno

Faecal samples were collected monthly from 504 Ethiopian highland sheep kept on station and in six farmers' villages around Sheno Agricultural Research Center during the period May 1995 - April 1996. Samples were examined microscopically to determine the class and species of parasites involved and the number of gastorintestinal nematode eggs per gram of faeces (EPG) using the sedimentation and floation techniques. Baerman techniques was also used to isolate infective larvae of H. contortus in faecal cultures from on-station animals. Eggs of Fasciola, Paramphistoma, moniezia and gastointestinal nematodes (strongyle), and larvae of Dictyocaulus flaria and Muellerius capillarius were identified as the prominent internal parasites of sheep in the Sheno area. Monthly prevalence of positive trematodes, cestode and lung nematodes indicated that maximum infection rates with Fasciola, Paramphistoma, Moniezia spp., D. filaria and M. capillarius were 47.6 percent, 50 percent, 23.8 percent, 6.7 percent and 30.9 percent, respectively. Peak intensity of lung nematodes occurred during the long rains from June to August and during the short rains from February to March. High prevalence rates of Fasciola occurred form april to June and in January. Mean EPG count of gastrointestinal nematodes varied from 103 in April to 879 in August. Differences in prevalence rates were observed due to variables such as sex, age, health status and faecal consistency. Mean monthly rainfall and monthly strongyle counts were found to be positively associatedIn general, strongyle faecal egg count and lung nematodes peaked during the long and short rainy seasons whereas the prevalence rate of Fasciola increased during the dry season in the months of January, April and May. It would, therefore, be effective to strategically de-worm animals at lush seasons and at least twice a year just before the on-set of the short and long rainy seasons (mid-June and mid-January) in-order to reduce worm burden and pasture contamination with eggs/larvae.