Studies on parasitic helminths of sheep and goats in Ghana

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    • "Therefore, goats not only play a vital role in ensuring food security of a household (often being the only asset possessed by a poor household), but in time of emergency (e.g. crop failure, family illness or school fees) goats may be sold to provide an important source of cash (Assoku 1980). Odeyinka and Torimiro (2006) described the pivotal roles that women and children played in WAD goat husbandry. "
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    • "Available records from field surveys and other epidemiological data indicate that WAD goats from all the countries of the region, such as Ghana [12], Mali [13], Nigeria [14] and Sierra Leone [15], are parasitized by essentially the same genera and species of GI nematodes namely: Haemonchus contortus and Trichostrongylus axei in the abomasum, T. colubriformis, Bunostomum trigonocephalum, Gaigeria pachyscelis, Cooperia curticei, C. punctata, and Strongyloides papillosus in the small intestine and Oesophagostomum columbianum, Trichuris ovis, T. globulosa and Chabertia ovina in the large intestine. However, the commonest and most important are H. contortus, T. colubriformis and O. columbianum [16]. "
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    ABSTRACT: West African Dwarf (WAD) goats serve an important role in the rural village economy of West Africa, especially among small-holder livestock owners. They have been shown to be trypanotolerant and to resist infections with Haemonchus contortus more effectively than any other known breed of goat. In this paper we review what is known about the origins of this goat breed, explain its economic importance in rural West Africa and review the current status of our knowledge about its ability to resist parasitic infections. We suggest that its unique capacity to show both trypanotolerance and resistance to gastrointestinal (GI) nematode infections is immunologically based and genetically endowed, and that knowledge of the underlying genes could be exploited to improve the capacity of more productive wool and milk producing, but GI nematode susceptible, breeds of goats to resist infection, without recourse to anthelmintics. Either conventional breeding allowing introgression of resistance alleles into susceptible breeds, or transgenesis could be exploited for this purpose. Appropriate legal protection of the resistance alleles of WAD goats might provide a much needed source of revenue for the countries in West Africa where the WAD goats exist and where currently living standards among rural populations are among the lowest in the world.
    Parasites & Vectors 02/2011; 4(1):12. DOI:10.1186/1756-3305-4-12 · 3.43 Impact Factor
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    • "In general, the combined effects of these factors are responsible for the seasonal fluctuations in the availability of L3 on pasture, and subsequently in the prevalence of worm burdens in the hosts. This seasonal variation of parasite population dynamics has been described in a number of studies in many African countries (Assoku, 1981; Vercruysse, 1983; Van Wyk, 1985; Fakae, 1990; Fritsche et al., 1993; Maingi et al., 1993; Pandey et al., 1994; Tilahun, 1995; Tembely et al., 1997; Nginyi et al., 2001; Debela, 2002). In general, rapid translation of eggs through to L3 occurs throughout most of the rainy seasons, and grazing animals acquire the highest infections during these times. "
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    ABSTRACT: A two-year epidemiology study of helminths of small ruminants involved the collection of viscera from 655 sheep and 632 goats from 4 abattoirs in eastern Ethiopia. A further more detailed epidemiology study of gastro-intestinal nematode infections used the Haramaya University (HU) flock of 60 Black Head Ogaden sheep. The parasitological data included numbers of nematode eggs per gram of faeces (EPG), faecal culture L3 larvae, packed red cell volume (PCV), adult worm and early L4 counts, and FAMACHA eye-colour score estimates, along with animal performance (body weight change). There were 13 species of nematodes and 4 species of flukes present in the sheep and goats, with Haemonchus contortus being the most prevalent (65–80%), followed by Trichostrongylus spp. The nematode infection levels of both sheep and goats followed the bi-modal annual rainfall pattern, with the highest worm burdens occurring during the two rain seasons (peaks in May and September). There were significant differences in worm burdens between the 4 geographic locations for both sheep and goats. Similar seasonal but not geographical variations occurred in the prevalence of flukes. There were significant correlations between EPG and PCV, EPG and FAMACHA scores, and PCV and FAMACHA scores. Moreover, H. contortus showed an increased propensity for arrested development during the dry seasons. Faecal egg count reduction tests (FECRT) conducted on the HU flocks, and flocks in surrounding small-holder communities, evaluated the efficacy of commonly used anthelmintics, including albendazole (ABZ), tetramisole (TET), a combination (ABZ + TET) and ivermectin (IVM). Initially, high levels of resistance to all of the anthelmintics were found in the HU goat flock but not in the sheep. In an attempt to restore the anthelmintic efficacy a new management system was applied to the HU goat flock, including: eliminating the existing parasite infections in the goats, exclusion from the traditional goat pastures, and initiation of communal grazing of the goats with the HU sheep and animals of the local small-holder farmers. Subsequent FECRTs revealed high levels of efficacy of all three drugs in the goat and sheep flocks, demonstrating that anthelmintic efficacy can be restored by exploiting refugia. Individual FECRTs were also conducted on 8 sheep and goat flocks owned by neighbouring small-holder farmers, who received breeding stock from the HU. In each FECRT, 50 local breed sheep and goats, 6–9 months old, were divided into 5 treatment groups: ABZ, TET, ABZ + TET, IVM and untreated control. There was no evidence of anthelmintic resistance in the nematodes, indicating that dilution of resistant parasites, which are likely to be imported with introduced breeding goats, and the low selection pressure imposed by the small-holder farmers, had prevented anthelmintic resistance from emerging.
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