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Title: Seasonal prevalence and distribution of ticks on the Accra Plains of Ghana and their association with dermatophilosis
Author: Koney, Enoch B. M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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The professional and scientific literature on the epidemiology, treatment and economic importance of dermatophilosis has been reviewed, particular attention being paid to the role of ticks, especially Amblyomma variegatum in causing overt disease and tick associated losses. In addition chemical and alternative methods of tick control including the use of resistant breeds of cattle, modification of vegetation and the microclimate, the introduction of tick-resistant grasses and host vaccination against ticks are discussed. An experiment herd of 26 animals and five local herds containing 605 animals on the coastal Plains of Ghana were studied. The seasonal abundance of ticks, their association with dermatophilosis and the systemic effects of the ticks on their hosts were investigated. Four genera, Amblyomma, Boophilus, Rhipicephalus and Hyalomma were identified on cattle, A. variegatum being the predominant tick species occurring throughout the year with peak infestations in the two rainy seasons. A highly significant positive correlation was revealed between A. variegatum and dermatophilosis in four of five local herds. Unexpectedly, a significant correlation was found between Hyalomma rufipes and dermatophilosis twice and between Rhipicephalus senegalensis and dermatophilosis once in the local herds. Clinical dermatophilosis developed two months after severe tick infestation. The immune responsiveness of tick-infested cattle were suppressed as assessed by the lymphocyte transformation test (LTT) and confirmed by [3H]-thymidine incorporation assays. Decreased lymphocyte responsiveness in the Friesian cattle coincided with peak tick levels and clinical dermatophilosis. In vitro lymphocyte responsiveness to Concanavalin A in culture medium containing foetal calf serum was suppressed by serum from cattle infested with ticks. Similarly, serum from cattle infested with ticks and infected with dermatophilosis suppressed lymphocytes derived from 'clean animals' i.e. control animals treated with acaricides.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available