A New Dawn By Sam Adewoye Pdf Download

Malaria infects over 250 million people and claims the lives of approximately 438,000 individuals annually. Approximately 90% of these deaths occur in Africa, predominantly in children aged 5 years and under [1]. Anopheles gambiae is the major vector of malaria in sub-Saharan Africa. Current control of malaria transmission is through control of the insect vector and efforts to reduce biting events that can result in disease transmission. As the female anopheline mosquito focuses its behavioural activity including blood-feeding to the night phase of the light:dark (LD) cycle, the mosquito bed net has become a key barrier method in malaria transmission control. However, it is fast becoming apparent that the efficacy of established methods of control, namely insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS) are compromised by both resistance to insecticides [2, 3] and by behavioural adjustments made presumably via changes in the genetic composition of the Anopheles vector mosquito populations [4,5,6,7,8,9,10,11]. It has been observed in various anophelines that the specific timing of biting activity can change under selective pressure, thereby resulting in a temporal shift. This can result in more biting events occurring either earlier in the night, dawn or during the early daytime (i.e. becoming daytime biters), and thereby make the efficacy of the bed net significantly reduced. It is for this reason that efforts are being made by the vector research community to develop new strategies to complement existing control methods, including control of outdoor residual mosquito populations. In line with this approach, we explored the efficacy of timed exposure to light as a potential method to reduce biting behaviour in An. gambiae mosquitoes.

In this study, we have developed a technique to reduce the incidence of biting and to disrupt the normal profile of nocturnal flight activity of the anopheline mosquito. Using exposure to white light presented at timed intervals during the late daytime, dusk, dawn, and during the night, we have demonstrated dramatic reductions in mosquito biting of humans as well as increased or decreased levels of mosquito flight activity, dependent upon the specific timing of light delivery. To reduce mosquito host-seeking and biting events, and thereby reduce malaria transmission, we propose that the photic exposure method could be used to augment current insect control techniques or be implemented as a stand-alone approach.

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To investigate the sustained biting inhibition effect observed earlier (Fig. 2), and assess its effectiveness as a method to inhibit biting throughout the night, we measured biting propensity every 2 h following precisely-timed light pulses presented every 2 h (Fig. 5). This protocol meant that mosquitoes assessed progressively later into the night would have received an accumulation of light pulses; i.e. mosquitoes assessed at ZT14 received one light pulse, mosquitoes assessed at ZT16 received two pulses, and mosquitoes assessed at ZT18, three pulses, and so on, such that the last population of mosquitoes to be tested for biting at CT24/0 received a total of six pulses. Light-treated mosquitoes displayed a significant decrease in biting propensity compared to controls. Significant differences between treatment and control were detected at ZT14, ZT16, ZT18 and CT24/0, but not at ZT20 or ZT22. While the suppressive effect of light upon biting can be observed at all phases of the night tested (i.e. the mean values for biting propensity are consistently lower than non-pulsed controls), clearly there is a distinct drop-off in efficacy of this sustained effect for 2 h during the late night (ZT20 and ZT22), followed by a return to robust suppression at the start of subjective dawn (CT24/0).

Based on the observations of these experiments, we expanded this approach to photic manipulation of the mosquitoes to develop a method to reduce biting propensity throughout the night by exposing mosquitoes to a series of light pulses presented every 2 h. We hypothesised that this protocol would result in a sustained inhibition of blood-feeding behaviour throughout the duration of the night. In this fourth experiment, the protocol elicited a sustained suppression of biting activity that was observed during the early to middle of the night, as well as at the very end of the night/dawn (ZT14, 16, 18 and CT0/24). While statistically significant differences were not observed for ZT20 and ZT22, the means for the pulsed groups were lower than the time matched control groups. This was somewhat surprising as we had hypothesised that the sustained response would be equal at all times of the night. However, these data suggest in a manner similar to the immediate responses tested in experiment 3, that the sustained effects of light are influenced by an underlying circadian property of the system. Additionally, the change in biting propensity may reflect an increased homeostatic drive to blood feed as the night progresses that then competes with the light-suppressive mechanism. However, despite the reduced efficacy of light delivered during the middle of the night, the sustained response using the multiple pulse approach provided suppression of biting during the early to middle night and late night/dawn phases of the night. As these times of night are critical phases of the diel cycle when humans are most susceptible to biting events as they are unprotected when not sleeping under a bed net, the results of the experiment suggest that indeed this multi-pulse method might be effective in the control of mosquito biting events in the field.

At present, insecticide-treated bed nets and indoor residual spraying of insecticides are heavily relied upon to prevent the transmission of malaria; however, as mosquitoes are becoming increasingly resistant to insecticidal treatments, and Plasmodium spp. become resistant to drug treatments [3, 57], there is a necessity for the ongoing development of novel and innovative control strategies. The current data illustrates the development of a method for the manipulation of mosquito biting and flight/locomotor activity behaviours using exposure to white light presented at timed intervals or during the late daytime, dusk, dawn, and during the night. This treatment may provide a useful method to augment current insect control methods, as well as acting alone, to reduce host-seeking (which involves flight) and biting events.

In the first theme, Falola and Aderinto map out the major historiographical perspectives in the production of historical knowledge in the Nigerian geographical region, especially with the consolidation of British imperial interests in the nineteenth century. Deftly analyzing methodological approaches and historiographical interpretations, they engage [End Page 156] problematic imperial interventions that have defined the meaning of Africa in the Western imagination, especially since the eighteenth century. As African diasporic thought acquired momentum after the British abolition of Atlantic slavery starting in 1807, pan-Africanist thinkers offered redemptive intellectual replies to prevailing Western distortions of the African past. Despite cultural nationalist tendencies, pan-Africanists were not predictable propagandists. As educators, journalists, and missionaries, they envisioned a Nigerian modernist project at the dawn of the twentieth century. They were precursors to the historical scholarship that shaped the analysis of two subsequent themes: the areas of historical studies, and the Nigerian nationalist historiography. e24fc04721