Deforestation and the spatio-temporal distribution of savannah and forest members of the Simulium damnosum complex in southern Ghana and south-western Togo

Show simple item record Wilson, M.D. Cheke, R.A. Flasse, S.P.J. Grist, S. Osei-Ateweneboana, M.Y. Tetteh-Kumah, A. Fiasorgbor, G.K. Jolliffe, F.R. Boakye, D.A. Hougard, J.-M. Yameogo, L. Post, R.J. 2019-02-28T10:34:02Z 2019-02-28T10:34:02Z 2002-11
dc.identifier.other Vol. 96(6): pp 632-9
dc.identifier.other DOI: 10.1016/S0035-9203(02)90335-4
dc.description.abstract Spatio-temporal data on cytotaxonomic identifications of larvae of different members of the Simulium damnosum complex collected from rivers in southern Ghana and south-western Togo from 1975 until 1997 were analysed. When the data were combined, the percentages of savannah blackflies (S. damnosum sensu stricto and S. sirbanum) in the samples were shown to have been progressively increasing since 1975. The increases were statistically significant (P < 0.001), but the rates of increase were not linear. Further analyses were conducted according to the collection seasons and locations of the samples, to account for possible biases such as savannah flies occurring further south in the dry season or a preponderance of later samples from northern rivers having more savannah flies. These analyses showed that the increasing trend was statistically significant (P < 0.0001) only during the periods April to June and October to December. The presence of adult savannah flies carrying infective larvae (L3) indistinguishable from those of Onchocerca volvulus in the study zone was confirmed by examinations of captured flies. The percentages of savannah flies amongst the human-biting populations and the percentages with L3s in the head were higher during dry seasons than wet seasons and the savannah species were found furthest south (5°25′N) in the dry season. Comparisons of satellite images taken in 1973 and 1990 over a study area in south-western Ghana encompassing stretches of the Tano and Bia rivers demonstrated that there have been substantial increases in urban and savannah areas, at the expense of forest. This was so not only for the whole images but also for subsamples of the images taken at 1, 2, 4, 8 and 16 km distant from sites alongside the River Tano. At every distance from the river, the percentages of pixels classified as urban or savannah have increased in 1990 compared with 1973, while those classified as degraded or dense forest have decreased. The possibility that the proportionate increases in savannah forms of the vectors of onchocerciasis, and hence in the likelihood of the transmission of savannah strains of the disease in formerly forested areas, were related to the decreases in forest cover is discussed. en_US
dc.language.iso en en_US
dc.publisher Transactions of the Royal Society of Tropical Medicine and Hygiene en_US
dc.subject Deforestation en_US
dc.subject Forest en_US
dc.subject Ghana en_US
dc.subject Onchocerciasis en_US
dc.subject Remote-sensing en_US
dc.subject Savannah en_US
dc.subject Simulium damnosum cytospecies en_US
dc.subject Togo en_US
dc.subject Transmission en_US
dc.title Deforestation and the spatio-temporal distribution of savannah and forest members of the Simulium damnosum complex in southern Ghana and south-western Togo en_US
dc.type Article en_US

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  • Parasitology Department [248]
    The Department of Parasitology conducts research into parasitic diseases of public health importance with the overall goal of reducing their transmission and the heavy disease burden that they impose on affected populations. The Department maintains focus on parasitic diseases in general. These include major diseases such as malaria, and others listed under the Neglected Tropical Diseases (NTD) control initiative such as, lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis, trypanosomiasis and leishmaniasis.

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