Browsing by Author "Garms, R."
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Item Assessments of the transmission of Onchocerca volvulus by Simulium sanctipauli in the Upper Denkyira District, Ghana, and the intermittent disappearance of the vector(Parasitology Research, 2015-01) Garms, R.; Badu, K.; Owusu-Dabo, E.; Baffour-Awuah, S.; Adjei, O.; Debrah, A.Y.; Nagel, M.; Biritwum, N.K.; Gankpala, L.; Post, R.J.; Kruppa, T.F.Following studies on the transmission of Onchocerca volvulus (Leuckart) by Simulium sanctipauli Vajime & Dunbar (Diptera, Simuliidae) in Upper Denkyira District in Ghana in 2001 and 2002 (Kutin et al., Med Vet Ent 18:167–173, 2004), further assessments were carried out in 2006 and 2013/2014 to determine whether transmission parameters had changed since community-directed ivermectin treatment (CDTI) began in 1999. There were no marked changes of the transmission intensities in 2006. Only slight, but non-significant, reductions were observed in infection rates of parous flies with larval stages (L1–L3) of O. volvulus from 44.1 % (of 1672 parous flies) in 2001/2002 to 42.1 % (506) in 2006 and from 6.5 to 5.9 % of flies carrying infective larvae in their heads. This suggested that there was an ongoing transmission in the area and the parasite reservoir in the human population was still high. Unexpectedly, further assessments conducted in October 2013 and March and October 2014 revealed that the vector S. sanctipauli had apparently disappeared and transmission had ceased, probably as a result of intensified gold mining activities along the rivers Ofin and Pra. The water of both rivers was extremely turbid, heavily loaded with suspended solids, probably preventing the development of blackfly larvae. Some breeding and biting of Simulium yahense Vajime & Dunbar was observed in a small tributary of the Pra, the Okumayemfuo, which is not affected by gold mining. However, the infection rate of flies was low, only 3.7 % of 163 parous flies were infected with first stage (L1) larvae of O. volvulus. © 2015, Springer-Verlag Berlin Heidelberg.Item Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa(Philosophical Transactions of the Royal Society B: Biological Sciences, 2015-04) Cheke, R.A.; Basáñez, M.-G.; Perry, M.; White, M.T.; Garms, R.; Obuobie, E.; Lamberton, P.H.L.; Young, S.; Osei-Atweneboana, M.Y.; Intsiful, J.; Shen, M.; Boakye, D.A.; Wilson, M.D.Development times of eggs, larvae and pupae of vectors of onchocerciasis (Simulium spp.) and of Onchocerca volvulus larvae within the adult females of the vectors decrease with increasing temperature. At and above 258C, the parasite could reach its infective stage in less than 7 days when vectors could transmit after only two gonotrophic cycles. After incorporating exponential functions for vector development into a novel blackfly population model, it was predicted that fly numbers in Liberia and Ghana would peak at air temperatures of 298C and 348C, about 38C and 78C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 298C and of savannah flies (Ghana) at 308C. Small temperature increases (less than 28C) might lead to changes in geographical distributions of different vector taxa. When the new model was linked to an existing framework for the population dynamics of onchocerciasis in humans and vectors, transmission rates and worm loads were projected to increase with temperature to at least 338C. By contrast, analyses of field data on forest flies in Liberia and savannah flies in Ghana, in relation to regional climate change predictions, suggested, on the basis of simple regressions, that 13–41% decreases in fly numbers would be expected between the present and before 2040. Further research is needed to reconcile these conflicting conclusions. © 2015 The Author(s) Published by the Royal Society. All rights reserved.