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Insecticide Resistance Status of Culex Species in Urban Areas in Ghana

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Insecticide Resistance Status of Culex Species in Urban Areas in Ghana Dissertation zum Erwerb des Doctor of Philosophy (Ph.D.) an der Medizinischen Fakultät der Ludwig-Maximilians-Universität zu München Doctoral Thesis for the awarding of a Doctor of Philosophy (Ph.D.) at the Medical Faculty of Ludwig-Maximilians-Universität, Munich vorgelegt von submitted by ____________________________________ aus (Geburtsort) born in (place of birth) ____________________________________ am (Tag an dem die Dissertation abgeschlossen wurde) submitted on (day of finalization of the thesis) __________________ Supervisors LMU: Title, first name, last name Habilitated Supervisor ______________________________ Direct Supervisor ___________________________ Supervisor External: Local Supervisor ______________________________ Reviewing Experts: 1st Reviewer ___________________________________________ 2nd Reviewer ___________________________________________ Dean: Prof. Dr. med. Dr. h. c. M. Reiser, FACR, FRCR Date of Oral Defence: ___________________________________________ Affidavit Surname, first name Street Zip code, town Country I hereby declare, that the submitted thesis entitled Thesis Title Thesis Title (cont.) Thesis Title (cont.) is my own work. I have only used the sources indicated and have not made unauthorised use of services of a third party. Where the work of others has been quoted or reproduced, the source is always given. The submitted thesis or parts thereof have not been presented as part of an examination degree to any other university. I further declare that the electronic version of the submitted thesis is congruent with the printed version both in content and format. Place, Date Signature PhD Student Key Words Culex, insecticide, insecticide-treated-material, insecticide-resistance, malaria control, nuisance, urban Abstract Background Current strategic plan for malaria control in Ghana includes the attainment of 80% of the general population sleeping under insecticide treated materials (ITM) by 2015. This coverage may not be attained if there is non-compliance in the use of bed nets. Failure of ITM to protect users from nuisance mosquitoes, particularly Culex mosquitoes has been cited as one of the major threats to the sustained use of ITM. A nationwide survey was therefore carried out to determine insecticide resistance status of Culex species and efficacy of ITM against them. Methods and materials Mosquito larvae were sampled from various land use and ecological settings and at different seasons. These were reared to adults and used for the various tests. In adults, insecticide susceptibility tests to eight insecticides as well as cone and tunnel bioassays were performed. Biochemical and molecular analyses were also conducted to determine the resistance mechanisms in the study populations. Results Culex quinquefasciatus and C. decens were the Culex species that were identified in the study area. DDT and deltamethrin resistances were evident across the country. A 1 strong relationship between resistance status and urban size was observed in the study population (Pearson χ2 =48.2; df = 1; P<0.0001). Not only kdr and ace1 mutations but also elevated levels of three detoxifying enzymes were found in the study populations. New ITMs evaluated had reduced efficacy against pyrethroid- resistant Culex mosquitoes. Conclusions Insecticide resistance status of Culex species in urban areas of Ghana was determined. Insecticide resistance level was high in large urban areas. Urbanization and its associated problems as well as ecology and different land use were observed to have some impact on level of insecticide resistance in the Culex population. ITM with synergist and organophosphate insecticides were seen as a possible resistance management tool against pyrethroid-resistant Culex mosquitoes. 2 Table of Content List of figures............................................................................................................. 6 List of tables.............................................................................................................. 8 List of appendices......................................................................................................10 Abbreviations..............................................................................................................11 1) Introduction ................................................................................................................................ 12 2) Literature review ....................................................................................................................... 14 2.1) Mosquito and human welfare ....................................................................................... 14 2.1.1) Biology and behaviour of mosquito ....................................................... 14 2.1.2) Impact of mosquito on human welfare .................................................. 18 2.1.3) Mosquito management strategies ......................................................... 20 2.2) Malaria and malaria control .......................................................................................... 22 2.2.1) Global burden of malaria ....................................................................... 22 2.2.2) Malaria vectors ...................................................................................... 23 2.3) Culex quinquefasciatus and public health ................................................................ 25 2.3.1) Biology and behavior of Culex quinquefasciatus ................................... 25 2.3.2) Potential impact of Culex quinquefasciatus on malaria control ............. 26 2.4) Insecticide use in public health and insecticide resistance ................................. 28 2.4.1) Insecticide use in vector control ............................................................ 28 2.4.2) Insecticide resistance in mosquitoes ..................................................... 30 2.4.3) Insecticide resistance mechanisms ....................................................... 31 2.5) Factors that select for insecticide resistance ........................................................... 36 2.5.1) The role of agriculture ........................................................................... 36 2.5.2) The role of public health ........................................................................ 37 2.5.3) The role of urbanization ........................................................................ 38 2.5.4) The role of microbial flora ..................................................................... 38 2.6) Insecticide resistance management ........................................................................... 39 2.7) Mosquito borne diseases in Ghana and control ..................................................... 40 2.7.1) Burden of malaria and other mosquito-borne diseases in Ghana ......... 40 2.7.2) Malaria control in Ghana ....................................................................... 42 2.7.3) Insecticide resistance profile in Ghana ................................................. 44 3 3) Rationale and Objectives ....................................................................................................... 47 3.1) Rational of the study ....................................................................................................... 47 3.2) Purpose of the study ....................................................................................................... 48 4) Methods ...................................................................................................................................... 49 4.1) Description of study area ............................................................................................... 49 4.2) Mosquito collection .......................................................................................................... 51 4.3) Susceptibility bioassay ................................................................................................... 56 4.4) Molecular analyses .......................................................................................................... 59 4.4.1) DNA extraction ...................................................................................... 59 4.4.2) Detection of kdr and ace1 mutation ...................................................... 61 4.5. Biochemical assays ......................................................................................................... 67 4.5.1) Non-specific esterase microplate assay ................................................ 70 4.5.2) Mixed-function oxidase microplate assay ............................................. 70 4.5.3) Glutathione S-Transferase microplate assay ........................................ 70 4.5.4) Protein assay ........................................................................................ 71 4.6. Evaluation of insecticide treated nets against pyrethroid-resistant Culex quinquefasciatus .............................................................................................................. 72 4.6.1) WHO cone test bioassay ...................................................................... 72 4.6.2) Tunnel test bioassay ............................................................................. 74 4.7. Statistical analyses .......................................................................................................... 77 5) Results .......................................................................................................................................
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