An epidemiological study on gastrointestinal nematodes of sheep was carried out in farms of small farmers in Hyderabad district from May 2004 to April 2005. Faecal egg counts, pasture larval counts and worm counts from permanent grazing animals were recorded for 12 months. H. contortus (24.6%) was found to be predominant of gastrointestinal nematode parasites, Trichostrongylus spp. (18.0%) was the next most prevalent species, others, including: O. circumcincta, S. papillosus, T. ovis, Oe. columbianum and Chabertia ovina were found in varying percentages. The highest faecal egg counts (FEC) were recorded in September, whereas the lower FEC were in February. Statistical analysis revealed that the FEC were significantly (P<0.01) affected by months (seasons). The peak of pasture infectivity was in August and declined to lower level in January. The mean worm burden counts were the highest in September and declined toward the minimum level in February in necropsized animals. The worm counts was influenced significantly (P<0.01) by FEC and pasture larval counts. The results of this study could be used to design a programme to minimize and control gastrointestinal nematode infections in sheep.

Key words: Epidemiology, gastrointestinal nematodes, sheep, faecal egg counts.