AFRICAN HORSE SICKNESS: STUDY ON SEROPREVALENCE AND DENTIFICATION OF RISK FACTORS IN EQUIDAE AT SELECTED SITES IN ETHIOPIA
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2006-06
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Abstract
A study was undertaken to determine the seroprevalence of African horse sickness virus antibodies, isolate and characterize the virus responsible as well as identify potential risk factors in the equine population of selected study areas in Ethiopia. In total 1265 serum samples originating from 824 donkeys, 383 horses and 58 mules were collected from September 2005 to mid of April 2006. Competitive Enzyme Linked Immunosorbent Assay (C-ELISA) configuration was employed to determine the presence of AHSV antibodies. The apparent prevalence of AHSV was found to be 29.7% (95% CI = 26.8-33.0) in donkeys, 10.4% (95% CI = 7.8-14.0) in horses and 10.3% (95% CI =4.8-22.1) in mules. The overall apparent seroprevalence of AHSV was found to be 23% (95% CI=20.8-25.4). There is significant variation amongst the types of equidae in seropositivity (P<0.05). Statistically significant (P<0.05) difference in seroprevalence was observed in the different study areas, confirming the existence of agro-ecology based variation in the occurrence of African horse sickness. The highest seroprevalence of AHSV was documented in the lowlands followed by midland and highland areas. This has direct correlation with the ecological distribution of the Culicoides vectors. As for age dependent variation in seroprevalence no statistical significant difference was found. All age groups as well as male and female populations were equally affected. The risk of acquiring AHS is more than two fold (OR = 2.1) with respect to the types of equidae affected. Moreover, agro-ecology contributes nearly two fold (OR =1.5) for the occurrence of African horse sickness. There is strong association among C-ELISA result of AHSV antibodies, types of equidae and agro-ecology, but age is not part of the interaction. However, sex has weak effect to precipitate the occurrence of African horse sickness. Active disease search was conducted with the aim of virus isolation and identification. After three blind passages were carried out on vero cell lines the sample was subjected to I-ELISA configuration. However, the result was negative. In the presence of the disease in the field with classical pathognomonic signs and postmortem lesions the negative result is probably due to the improper handling of the tissues processed. The indigenous knowledge base of equine owners about African horse sickness in the study areas was assessed through a structured questionnaire format. The survey result indicated that, the indigenous knowledge of owners was found to be unsatisfactory.
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Equidae, AHSV, Seroprevalence, Risk factors, C-ELISA