Browsing by Author "Dadzie, S. K."

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    Characterization of Malaria Transmission and Insecticide Susceptibility Status of Anopheles Gambiae Sensu Lato Gilles (Diptera: Culicidae) In Shai-Osudoku District of Southern Ghana
    (University of Ghana, 2015-07) Ononye, N. C.; Dadzie, S. K.; Aboagye-Antwi, F.; Kyerematen, R.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS)
    Malaria is a major public health problem in most developing countries. In Ghana, it is hyper-endemic with children under-five years, pregnant women and non-immune visitors being at greatest risk. The National Malaria Control Programme recognizes the use of Insecticide-Treated Nets (ITNs) as one of the multiple prevention tools in the control of the malaria vectors. But due to problems associated with ITNs which include rapid loss of bio-efficacy as a result of repeated washings and low re-treatment rates, long-lasting insecticide-treated nets (LLINs) have been developed. For new LLINs, evaluation in the field is required before they are recommended for use in malaria vector control. A site in the Shai-Osudoku district in southern Ghana has been proposed for testing new LLIN products. In preparation for such field trial, baseline data on indices of malaria transmission such as species composition, man-biting rate, sporozoite rates and entomological inoculation rates (EIR) as well as insecticide susceptibility status and resistance mechanism in the main malaria vector were investigated in some communities in Asutsuare area, a sub-district of Shai-Osudoku district. Mosquito larvae and pupae were collected using dipping method, reared to the adult stage and used for the insecticide susceptibility bioassays. Adult mosquitoes were sampled using human landing catches and pyrethrum spray catches. These were morphologically identified and then to sibling species of the Anopheles gambiae complex by the polymerase chain reaction (PCR) assay. Identified An. gambiae s.s. were further subjected to PCR assays for the identification of the molecular forms and the detection of the leucine to phenylalanine knockdown resistance (kdr) gene mutation. The heads and thoraces of An. gambiae samples were tested for the presence of circumsporozoite antigens/proteins of Plasmodium falciparum using the enzyme-linked immunosorbent assay (ELISA) method. The susceptibility bioassays were carried out using the standard WHO diagnostic bioassay kits and were performed on non-blood fed female mosquitoes of 2- to 5- day old. A total of 3,410 mosquitoes were collected from the four communities during the study period. 85.9% were Culicines, 12.2% An. gambiae s.l., 1.2% An. pharoensis, 0.6% An. coustani and 0.2% An. funestus. An. gambiae s.s. was the only identified member of the An. gambiae s.l. and it consisted of both the An. coluzzii and S molecular forms, with An. coluzzii being predominant (98.9%). No hybrids of the two molecular forms were found. Higher proportion of An. gambiae at the study sites (with exception of Volivo/Atrobinya) were observed biting indoors relative to outdoors with peak biting activity in the second, third and fourth quarters of the night. Man-biting rate was higher in Kewum as compared with the rest of the study sites. Sporozoite rate of 0.24 % and an overall annual Entomological Inoculation Rate (EIR) of 4.9 infective bites per man per year (ib/m/y) were estimated in the study sites. The susceptibility test results showed that An. gambiae populations in Asutsuare are resistant to all the pyrethroids (deltamethrin, permethrin, lambdacyhalothrin, cyfluthrin and etofenprox) insecticides tested but highly resistant to permethrin. The estimated frequency of knockdown resistance (kdr) genotypes F(R) was 77%, which is a good criterion for testing LLINs that are effective against resistant mosquitoes under field conditions.