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University of Nairobi (2002)

Epidemiology and control of Gastrointestinal Helminth infections in sheep in a semi-arid area of Kajiado district of Kenya

Chege, JN

Titre : Epidemiology and control of Gastrointestinal Helminth infections in sheep in a semi-arid area of Kajiado district of Kenya

Auteur : Chege, JN

Université de soutenance : University of Nairobi

Grade : Doctor of Philosophy (Ph. D) 2002

Résumé partiel
Gastrointestinal helminth parasites impose severe economic constraints on sheep production worldwide. For rational and sustainable control of these parasites, comprehensive knowledge on the epidemiology of the parasite as it interacts with the host in a specific climatic, management and production environment is crucial. The helminth infections have primarily been controlled by use of anthelmintics due to their ease of application and high efficiency. However, in developing countries, there are poor or ineffective set plans of prophylactic control of gastrointestinal helminths and the use of anthelmintics is mainly irregular and haphazard. No previous information was available on the epidemiology and control strategies of gastrointestinal helminths of sheep in the semi-arid area of Kajiado District. The main objective of this thesis was therefore to establish the epidemiology and control strategies of gastrointestinal helminths in sheep in this area. A survey on the prevalence and intensity of infection with gastrointestinal helminths of sheep in relation to age, breed and weather factors was carried out during the period May 1999 to May 2000. Faecal samples from Dorper and Red Maasai lambs, yearlings and adult breeding ewes were examined for helminth egg output and species composition. The results indicated that the prevalence and intensity of strongyles and tapewonns infections were highest for lambs and lowest for the yearlings in both breeds. The proportions of infected animals were higher during the wet season than in the dry season. Mixed infections were detected in both breeds of sheep where Trichostrongylus (53 %), Haemonchus (29.5 %), Cooperia (11.3 %) and Oesopliagostomum (6.2 %) were the most frequently encountered species throughout the study period. The prevalence of infection with gastrointestinal nematodes was significantly higher (p < 0.05) for the Dorpers than the Red Maasai in all the age groups. The findings indicated that the prevalence and intensities of infection with gastrointestinal helminths in this area were influenced by the age of the host, the breed and weather factors. An investigation on the occurrence of peri-parturient rise in trichostrongylid nematode egg output in breeding ewes was carried out for 3 breeding seasons during the period June 1999 to December 2001. Each season, 20 ewes randomly selected from the breeding stock and 20 others selected from the un-mated yearlings were examined. A significant peri-parturient rise in faecal egg output occurred at around the time of lambing and throughout the lactation period in the mated ewes, but not in the un-mated yearlings. Higher peri-parturient rise in faecal egg output occurred when lambing coincided with the end of the dry season before the short rains, a time when the resumption of development of hypobiotic larvae occurred. The occurrence of peri- parturient rise in breeding ewes contributed to higher pasture contamination at a time when the number of susceptible lambs were increasing.

Subject : Gastrointestinal Helminth infections ; Epidemiology ; Kenya ; semi-arid areas

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Page publiée le 2 octobre 2014, mise à jour le 29 décembre 2017