Pakistan Vet. J., 2008, 28(3): 125-130. 125 EPIDEMIOLOGY OF OVINE GASTROINTESTINAL NEMATODES IN HYDERABAD DISTRICT, PAKISTAN I. R. M. AL-SHAIBANI, M. S. PHULAN, A. ARIJO AND T. A. QURESHI 1 Department of Veterinary Parasitology, 1 Department of Veterinary Pharmacology, Sindh Agriculture University, Tando Jam, Pakistan ABSTRACT 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. INTRODUCTION Helminthiasis in small ruminant affects production losses due to mortalities, reduce weight gain and other losses of production (Chaudary et al., 2007). However, the effects of helminth infections on production of particular livestock species depend mostly upon the age of the animal, breed, parasite species involved and the intensity of the worm population. Several factors are known to determine the epidemiological pattern of the associated disease condition. These include weather condition, husbandry practice, and the physiological status of the animal (Khan et al., 1989; Tembely et al., 1997; Wall et al., 2004). For rational and sustainable control of helminth parasites especially the gastrointestinal nematodes of sheep, a comprehensive knowledge of the epidemiology of parasites and their interaction with the host in a specific climate and management practice is a prerequisite (Pal and Qayyum, 1992; Keyyu et al., 2005). This study was carried out to investigate some epidemiological aspects of gastrointestinal nematodes of sheep in Hyderabad district, Pakistan. MATERIALS AND METHODS Animals and management The study was conducted for a period of 12 months from May, 2004 to April, 2005 in five areas of Hyderabad district including Hyderabad city, Tandojam, Tando Allahyer, Tando Muhammad Khan and Hallah. This area is situated in irrigated agro- ecological zone in the province of Sindh, Pakistan. Sheep of various local breeds, sexes, and age groups were randomly selected from small farmers. The animals were maintained under the semi-intensive management system and were released during the day for grazing and housed overnight. Traditionally, in study areas, small ruminant feeding was based on grazing with occasional supply of crop residues and household wastes. Faecal samples A total of 1200 faecal samples of sheep were collected from 20 selected farms/flocks of small farmers in study areas. The faecal samples were collected directly from rectum of sheep. All samples were individually analyzed for qualitative and quantitative examination. Faecal egg counts (FEC) were carried out by using a modified McMaster technique (Urquhart et al., 1996). Positive samples were pooled for each farm and cultured for identification of nematode species according to the techniques described by MAFF (1986). Pasture larval counts The herbage samples were collected from five communal grazing pastures of Hyderabad district including Hyderabad city, Tandojam, Tando Allahyar, Tando Muhammad Khan and Halla. The samples were collected at fortnight intervals for a period of 12 months. The grazing areas were traversed in a ‘W” shape route stopping every 5-10m and small wisp of pasture were picked by hand/scissors, collected in