Department of Animal Biology and Conservation Science (DABCS)
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Item Bulk‐up synchronization of successive larval cohorts of Anopheles gambiae and Anopheles coluzzii through temperature reduction at early larval stages: effect on emergence rate, body size and mating success(Malaria Journal, 2021) Zubair, Q.; Matthews, H.; Sougoufara, S.; Mujeeb, F.; Ashall, S.; Aboagye‑Antwi, F.; Tripet, F.Background: Malaria persists as a huge medical and economic burden. Although the number of cases and death rates have reduced in recent years, novel interventions are a necessity if such gains are to be maintained. Alternative methods to target mosquito vector populations that involve the release of large numbers genetically modified mosquitoes are in development. However, their successful introduction will require innovative strategies to bulk-up mosquito numbers and improve mass rearing protocols for Anopheles mosquitoes. Methods: The relationship between mosquito aquatic stage development and temperature was exploited so that multiple cohorts of mosquitoes, from separate egg batches, could be synchronized to ‘bulk-up’ the number of mosquitoes released. First instar larvae were separated into two cohorts: the first, maintained under standard insectary conditions at 27oC, the second subjected to an initial 5-day cooling period at 19oC. Results: Cooling of 1st instars slowed the mean emergence times of Anopheles coluzzii and Anopheles gambiae by 2.4 and 3.5 days, respectively, compared to their 27oC counterparts. Pupation and emergence rates were good (> 85 %) in all conditions. Temperature adjustment had no effect on mosquito sex ratio and adult fitness parameters such as body size and mating success. Conclusions: Bulk-up larval synchronization is a simple method allowing more operational flexibility in mosquito production towards mark-release-recapture studies and mass release interventions.Item Characterization of Anopheles gambiae s.l. and insecticide resistance profile relative to physicochemical properties of breeding habitats within Accra Metropolis, Ghana(Tanzania Journal of Health Research, 2011-07) Kabula, B.I.; Attah, P.K.; Wilson, M.D.; Boakye, D.A.Malaria is endemic in Ghana as in most countries of sub-Saharan Africa. This study was conducted to characterize Anopheles gambiae s.l. and determine pyrethroid resistance profiles relative to physicochemical properties of breeding habitats in Accra, Ghana. Eight aquatic habitats containing Anopheles larvae were identified and from each habitat, larvae and water were sampled. Adult An. gambiae reared from larvae were morphologically identified and tested for permethrin (0.75%) and deltamethrin (0.05%) resistance using WHO bioassay method. An. gambiae s.s. found were identified to their molecular levels and kdr mutation detected using PCR-based methods. Twenty-nine physicochemical parameters of each water sample were measured and their levels connected with pyrethroid resistance and proportions of An. gambiae s.s. molecular forms in habitats. A total of 2,257 mosquitoes were morphologically identified as An. gambiae s.l. and all 224 processed for PCR were identified as An. gambiae s.s., of which 56.46% and 43.54% were M and S-forms, respectively. Both forms occurred in sympatry in all larval habitats and no S/M hybrids were detected. However, M-form larvae were in high proportion in polluted habitats than the S-form. An. gambiae s.s. was highly resistant to both deltamethrin and permethrin with mortality rates of 42.98-70.0% and 6.5-20.0% respectively. The frequency of kdr mutation was 60.5% (n=195). This mutation occurred in both S and M-forms, but was mainly associated with the S-form (X 2=10.92, df =1, P=0.001). Carbonate and pH were both selected in discriminant function analysis as best predictors of high proportion of M-form in the habitats. The adaptation of An. gambiae s.s. in polluted aquatic habitats coupled with occurrence of insecticide resistance is quite alarming particularly for urban malaria control and needs further exploration in a wider context.Item Studies on the feeding behaviour of larvae of the predaceous mosquito culex (LUTZIA) tigripes grandpre and chamoy (üIPTERA: CULICIDAE)(Insect Science and its Application, 2000-12) Appawu, M.A.; Dadzie, S.K.; Quartey, S.Q.Experiments were carried out to determine the factors that influence the feeding behaviour of Cnkx tigripes, a mosquito whose larvae are predators of other mosquito larvae. The results indicated that the efficiency of predatory activities of Cx tigripes larvae increased as they developed from 1st to 4th instar with regard to the number of mosquito prey larvae they consumed in a given period of time. Fourth instars of Cx tigripes are the most voracious of all the stages and are better adapted for catching and consuming all stages of mosquito larvae. The mean number of mosquito larvae consumed in 24 hours increased with increasing prey density. When offered a mixture of different prey species and larval stages, Cx tigripes larvae consistently selected 4th instars of mosquitoes over pupae and preferred Acdes negypti larvae to the larvae of Cx qiiinquefasciatns and Anopheles gambiae. Prey size, density and mobility were also found to influence prey selection by Cx tigripes. ©2000ICIPE.Item Bio-efficacy, user perception and acceptability of pyrethroid based mosquito coils in controlling Anopheles gambiae s.l., in some parts of Accra, Ghana(Japanese Journal of Medical Entomology and Zoology. Vol. 65 No. 3p. 139-145, 2014) Adu-Acheampong, S.; Kyerematen, R.; Dadzie, S.; Appawu, M.; Boakye, D.; Williams, J.This study was to provide baseline information on patterns of coil usage, user acceptability and susceptibility levels of mosquito coils in some parts of Accra, Ghana. Three hundred and twenty questionnaires were administered to obtain information on knowledge and perception of respondents on the usage of mosquito coils. Adult Anopheles gambiae mosquitoes were tested for resistance to pyrethroid based mosquito coils using WHO standard protocol for testing household insecticide products. A total of 152 out of 320 respondents were direct users of coils. Close to 62% of this number frequently changes brands of coil they use. Over 61% of coil users indicated their willingness to continue to use coils even though there are adverse effects after use. Anopheles gambiae s.s. was the only species that was found in the study area. Mortalities of An. gambiae s.s. after exposure to coils were 37% for Angel®, 37.5% for Lord® and 15% for Heaven mosquito coil brands. More than half of the inhabitants in the area used coils to prevent mosquito bites. However, high levels of resistance was detected for all the three pyrethroid-based coils because West African kdr was detected in about 59% of samples of Anopheles gambiae s.s. that survived the exposure.