A cross-sectional study was carried out to determine the prevalence and risk factors associated with
ovine gastrointestinal nematode infestation by faecal examination of 408 sheep from five different sites
in and around Asella, South Eastern Ethiopia. The mean eggs per gram (EPG) count determined using
modified McMaster technique showed that 73 (30.04%) of the sheep were lightly infested, 98 (40.34%)
moderately infested and 72 (29.62%) heavily infested. Out of the total sampled sheep, 278 (68.1%) had a
gastrointestinal nematode infection. Strongyles were the most frequently (64.0%) recovered nematode
eggs followed by Strongyloides (7.4%) and Trichuris species (3.7%). The prevalence of gastrointestinal
nematode infection showed a significant difference (p < 0.05) between young and adult age groups, and
animals with poor body condition had a significantly higher worm egg count (p < 0.05) than those sheep
in moderate or good body condition. There was significant association between the gastrointestinal
nematode infection and animals with different age group, and body condition. In addition, there was a
significant difference (p < 0.05) in prevalence among months of the study period. There was no
significant difference (p > 0.05) in prevalence between sexes and different study sites of the subject
area. Due to its important health problem and impact on production in the study area, emphasis should
be given for the control and prevention of gastrointestinal nematode infection with further studies on
species identification and larval ecology.