Introduction Poverty, malnutrition, ill health with high mortality, unem- ployment and illiteracy with other poor social services, and hence reliability on foreign aid to sustain the life of ever- increasing human population are the main features of Ethiopia [18]. Intensification of poultry farming for egg and meat production is an efficient way to bridge most of these social gaps by supplying food, income and employment. However, such system of chicken production has the unfor- tunate consequences that disease outbreak of various etiolo- gies occur more frequently. Poultry production in Ethiopia can be classified into three categories namely : traditional, small-scale and large-scale commercial farms. The former is based on indigenous chic- ken types whereas the later two production systems are cha- racterized by more intensively managed exotic chicken lines [3]. Hence, local chicken production in Ethiopia is limited to traditional family-based free-range scavenging management system. The attempts have been made to raise indigenous (local) chickens under confined management in different research stations situated in various geographical areas of the country [16], [1], [5]. However, the repeated attempts have faced serious problem of high morbidities and mortalities. This has led to a tendency to conclude that indigenous chic- kens of Ethiopia are unfit for confined management [13]. The probable disease agents, which have been suspected for such morbidities and mortalities in confinement, were repor- ted to be coccidiosis, chronic respiratory disease, Marek’s disease and Salmonella pollurum and nutritional deficiencies [15]. Marek’s disease (MD) is a cell-associated, highly conta- gious, and economically important oncogenic or paralytic viral disease of poultry. It is caused by a herpes virus, which Marek’s disease in local chicken strains of Ethiopia reared under confined management regime in central Ethiopia R. DUGUMA 1 *, A. YAMI 1 , N. DANA 1 , F. HASSEN 1 and W. ESATU 1 1 Ethiopian Agricultural Research Organization Debre Zeit Agricultural Research Center P.O.Box 32 - Fax : +251-1-338061 * Corresponding author : E-mail : retadhuga@yahoo.com RÉSUMÉ La maladie de Marek chez des poulets autochtones Ethiopiens élevés sous un régime confiné en Ethiopie centrale. Par R. DUGUMA, A. YAMI, N. DANA, F. HASSEN et W. ESATU. La prévalence, les manifestations cliniques et pathologiques et la morta- lité liées à la maladie de Marek (MM) chez les poulets éthiopiens élevés en gestion confinée au Centre Agricole de Recherches de Debre Zeit, Ethiopie centrale, ont été étudiées pendant la période allant de novembre 2003 à jan- vier 2004. Les symptômes, la mortalité, les examens nécropsiques et micro- scopiques ainsi que les résultats d’essais virologiques et sérologiques ont été mis en oeuvre pour cette étude. Les données obtenus à partir de 503 pou- lets indigènes (28 Jarso, 84 Konso, 88 Tepi, 151 Tilili et 148 Horro) ont été analysées. L’étude montre une différence significative entre la manifestation des signes cliniques aigüs (65.2%) et chroniques (34.8%), respectivement (p<0.01). Il y a également une différence significative entre les écotypes sur la manifestation et les formes de la maladie (p<0.01). La mortalité globale était également très importante (p<0.01). L’évaluation de la mortalité en fonction des différents âges et des écotypes de poulet a permis de mettre en évidence une différence significative (p<0.01). Dans cette étude, 97.9% de poulets malades sont morts de la maladie. L’examen nécropsique a mis en évidence des lésions tumorales dans la plupart des viscères et des tissus ner- veux. L’étude sérologique de prévalence par essai d’immuno-diffusion de gel d’agar (AGID) réalisée sur 70 poulets indigènes aléatoirement prélevés a indiqué un taux global de prévalence de 72.9%. La prévalence d’anticorps de MM n’était pas significativement différente en fonction des écotypes de poulet. Le résultat de cette étude donne une indication pour laquelle les pou- lets indigènes ne sont pas adaptés à l’élevage confiné. MM est un problème de santé publique. Par conséquent, cette étude montre le besoin de vaccina- tion contre cette pathologie. Il semble désormais important de réaliser une étude sur l’efficacité des vaccins disponibles contre la MM, dans les condi- tions d’élevage liées à la gestion confinée des animaux. Mots-clés : Gestion confinée - poulets indigènes - la maladie de Marek - mortalité - Ethiopie. Revue Méd. Vét., 2005, 156, 11, 541-546 SUMMARY The prevalence, clinical and pathological manifestations and extent of mortality due to Marek’s disease (MD) was investigated from November 2003 to January 2004 among indigenous chickens of Ethiopia reared under confined management at the Debre Zeit Agricultural Research Center, central Ethiopia. Clinical signs, mortalities, gross and microscopic examinations as well as virological and serological test results were used for the study. Data from 503 local chickens (28 Jarso, 84 Konso, 88 Tepi, 151 Tilili and 148 Horro) were analyzed. The study indicated an overall signifi- cant difference between manifestation of clinical signs in acute (65.2 %) and chronic forms (34.8), respectively (p< 0.01). There was also significant dif- ference among ecotypes in manifestation and forms of MD (p< 0.01). The overall mortality was also very high (p<0.01). Mortality assessment among age and chicken ecotypes revealed a significant difference (p< 0.01). MD fatality rate was very high in this study where 97.9% diseased birds died. Post mortem investigation revealed nodular tumorous lesions in most vis- ceral organs. Histopathological investigation revealed lymphocyte infiltra- tion of visceral organs and nervous tissues. Serological prevalence study of MD using the Agar gel immuno-diffusion test (AGID) technique on 70 ran- domly sampled local chickens revealed an overall prevalence rate of 72.9 %. MD antibody prevalence was not significant among chicken eco- types. The result of the present study gives a hint for the possible reason behind the report that local chickens are unfit for confined management. MD was a serious health problem, and hence, from this study evidence is emerging to suggest the need for MD vaccination while rearing local chic- kens under confined management. Further detailed study on MD in local chickens and on the effectiveness of available MD vaccines in reducing the incidence of morbidity and mortality of local chickens under confined management is recommended. Keywords : Confined management - Local chickens - Marek’s disease - Mortality - Ethiopia.