Epidemiology of Gastrointestinal Tract Nematodiosis of Small Ruminants in Three Different Agro-Ecological Zones of Southern Ethiopia
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2005-06
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Abstract
An epidemiological study on gastrointestinal tract nematodiosis of small ruminants in three different agro-ecological zones of southern Ethiopia was carried out from August 2004 to April 2005 on 180 gastrointestinal tracts and 2,828 faecal samples collected from sheep and goats to identify nematode species, determine the occurrence and factors related to the nematode infection. The study was carried out through post-mortem examination and coprological examinations using floatation and McMaster egg counting methods. Post mortem examination revealed the existence of ten (10) nematode species with different percent prevalence rates (Oesophagostomum columbianum, 92.2; Trichostrongylus colubriformis, 73.9; Haemonchus contortus, 68.9; Trichostrongylus axei, 61.7; Tricuris ovis, 42.8; Bunostomum trigonocephalum, 18.9; Teladorsagia spp., 15.6; Trichostrongylus probolurus, 5.0; Strongyloides papillosus, 1.1 and Cooperia curticei, 0.5). The identification of Teladorsagia spp. and Trichostrongylus probolurus was new to the region and even to the country after Graber, (1975) and the identification of Cooperia curticei was for the first time in Ethiopia. The prevalence of gastrointestinal tract nematodiosis varies from 98.3% in lowland and midland agro-ecology to 100% in highlands, with an overall prevalence of 98.9% in all agro-ecological zones. The variation in the prevalence of individual nematode species on agro-ecological basis was significant (P<0.05) except for Oesophagostomum columbianum and Strongyloides papillosus (p>0.05). The seasonal point prevalence of Haemonchus contortus, Trichostrongylus axei, Bunstomum trigonocephalum, Oesophagostomum columbianum, Trichuris ovis and Trichostrongylus colubriformis were significantly varied (p< 0.05) between seasons of the year. Mean nematode burden of different seasons of the year have shown significant differences for seasonal variation (p<0.05). These variations were observed between seasons of late wet and early dry (p<0.05), late wet and mid dry (p<0.05), late wet and late dry (p<0.05), late wet and early wet (p<0.05) and between agro-ecological zone of highland and lowland (p<0.05). Sex difference and species variation did not show difference in the mean worm burden (p> 0.05). Out of 98.9% of infected animals in the study area, 97.7% were infected by more than one nematode species. 64.0% of poly-parasitised animals in the study area were infected by 4 or more nematode species. 58.4% of the infected animals harboured light infestation, 40.5% were moderate and only 1.1% was severely infected by gastrointestinal tract nematode species. The mean total nematode burden and mean total epg count both from slaughtered animals in this study was positively correlated (Spearman’s rho (rs)=0.57, p<0.001) and the correlation of mean epg to individual nematode species burden was significant for three nematode species; Trichostrongylus colubriformis, (rs=0.50); Haemonchus contortus, (rs=0.45) and Oesophagostomum columbianum, (rs=0.39) with p<0.001 for all correlations. Faecal examination results from population of sheep and goats during four sampling periods indicated significant seasonal variation (p<0.05) for all study sites. Majority of infected animals had a faecal egg count in the range of 50-800 epg and only few proportions of animals had faecal egg count over 1200.
The widespread existence of various nematodes in the form of polyparasitism both in sheep and goats in all agro-ecology of the study area, and the high nematode burden both at postmortem and coproscopic examination suggest the institution of various control measures including strategic anthelmintic treatment for efficient utilization of the available small ruminant resources at hand.
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Epidemiology, GIT nematodes, Postmortem, Coproscopy, Small ruminant