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Wanji S, Kengne-Ouafo JA, Esum ME, Chounna PWN, Tendongfor N, Adzemye BF, Eyong JEE, Jato I, Datchoua-Poutcheu FR, Kah E, Enyong P, Taylor DW. Situation analysis of parasitological and entomological indices of onchocerciasis transmission in three drainage basins of the rain forest of South West Cameroon after a decade of ivermectin treatment. Parasit Vectors 2015; 8:202. [PMID: 25886166 PMCID: PMC4393872 DOI: 10.1186/s13071-015-0817-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 03/19/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Community-Directed Treatment with Ivermectin (CDTI) is the main strategy adopted by the African Programme for Onchocerciasis control (APOC). Recent reports from onchocerciasis endemic areas of savannah zones have demonstrated the feasibility of disease elimination through CDTI. Such information is lacking in rain forest zones. In this study, we investigated the parasitological and entomological indices of onchocerciasis transmission in three drainage basins in the rain forest area of Cameroon [after over a decade of CDTI]. River basins differed in terms of river number and their flow rates; and were characterized by high pre-control prevalence rates (60-98%). METHODS Nodule palpation and skin snipping were carried out in the study communities to determine the nodule rates, microfilarial prevalences and intensity. Simulium flies were caught at capture points and dissected to determine the biting, parous, infection and infective rates and the transmission potential. RESULTS The highest mean microfilaria (mf) prevalence was recorded in the Meme (52.7%), followed by Mungo (41.0%) and Manyu drainage basin (33.0%). The same trend was seen with nodule prevalence between the drainage basins. Twenty-three (23/39) communities (among which 13 in the Meme) still had mf prevalence above 40%. All the communities surveyed had community microfilarial loads (CMFL) below 10 mf/skin snip (ss). The infection was more intense in the Mungo and Meme. The intensity of infection was still high in younger individuals and children less than 10 years of age. Transmission potentials as high as 1211.7 infective larvae/person/month were found in some of the study communities. Entomological indices followed the same trend as the parasitological indices in the three river basins with the Meme having the highest values. CONCLUSION When compared with pre-control data, results of the present study show that after over a decade of CDTI, the burden of onchocerciasis has reduced. However, transmission is still going on in this study site where loiasis and onchocerciasis are co-endemic and where ecological factors strongly favour the onchocerciasis transmission. The possible reasons for this persistent and differential transmission despite over a decade of control efforts using ivermectin are discussed.
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Affiliation(s)
- Samuel Wanji
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Jonas A Kengne-Ouafo
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Mathias E Esum
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Patrick W N Chounna
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Nicholas Tendongfor
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Bridget F Adzemye
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Joan E E Eyong
- Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon. .,Department of Biological Sciences, Faculty of Science, University of Bamenda, P.O. Box 39, Bambili, North West Region, Bamenda, Cameroon.
| | - Isaac Jato
- Tropical Medicine Research station, P.O. Box 55, Kumba, Cameroon.
| | - Fabrice R Datchoua-Poutcheu
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Research Foundation for Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon.
| | - Elvis Kah
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Department of Geography, University of Yaounde1, Yaounde, Cameroon.
| | - Peter Enyong
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon. .,Tropical Medicine Research station, P.O. Box 55, Kumba, Cameroon.
| | - David W Taylor
- Division of Pathway Medicine, School for Biomedical Studies, University of Edinburgh, 49 Little France Crescent, Edinburgh, EH16 4SB, UK.
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Richman AM, Dimopoulos G, Seeley D, Kafatos FC. Plasmodium activates the innate immune response of Anopheles gambiae mosquitoes. EMBO J 1997; 16:6114-9. [PMID: 9321391 PMCID: PMC1326295 DOI: 10.1093/emboj/16.20.6114] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Innate immune-related gene expression in the major disease vector mosquito Anopheles gambiae has been analyzed following infection by the malaria parasite, Plasmodium berghei. Substantially increased levels of mRNAs encoding the antibacterial peptide defensin and a putative Gram-negative bacteria-binding protein (GNBP) are observed 20-30 h after ingestion of an infected blood-meal, at a time which indicates that this induction is a response to parasite invasion of the midgut epithelium. The induction is dependent upon the ingestion of infective, sexual-stage parasites, and is not due to opportunistic co-penetration of resident gut micro-organisms into the hemocoel. The response is activated following infection both locally (in the midgut) and systemically (in remaining tissues, presumably fat body and/or hemocytes). The observation that Plasmodium can trigger a molecularly defined immune response in the vector constitutes an important advance in our understanding of parasite-vector interactions that are potentially involved in malaria transmission, and extends knowledge of the innate immune system of insects to encompass responses to protozoan parasites.
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Affiliation(s)
- A M Richman
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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