Human Habitats and Malaria Vector Control in Benin: Current Situation and Implications for Effective Control

Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) are the main indoor malaria vector tools control tools. The study examined housing characteristics and investigated the relationship between the total volume of household possessions, the volume of the sleeping room, and the hanging of LLINs. A total of 831 bedrooms were randomly selected in Benin in 2015. The findings showed that mud walls were predominant in rural areas (more than 75%), while metal roofs were common (77.3% - 97.9%). Battery-powered lighting was prevalent in rural areas in Northern (97%), while open-flame oil lamps were commonly used in rural areas in Southern (86%). The availability of correct bedding was low, ranging from 1% to 10% in all households. 20% of the bedrooms had at least 50% of their volume occupied by household possessions in urban areas. In rural areas, bedrooms without LLINs had a lower mean rate ratio of the volume occupied by possessions per the total volume of the room compared to bedrooms with at least one LLIN installed (p < 0.0001). The characteristics of human habitats are not favourable to the correct use of vector control intervention indoors. It is therefore important to improve people’s living conditions as the next step for malaria elimination.

Astrodaucus persicus as a new source of bioinsectisides against malaria vector, Anopheles stephensi

Objective: To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi(An. stephensi).Methods: Twenty five third instar larvae of An. stephensi were exposed to various concentrations(10–160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment.Results: Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values(LC_(50) and LC_(90)) of34.49 g/L and 108.61 g/L, respectively. Chloroform fraction of fruits extract was the second larvicidal sample with LC_(50) of 45.11 g/L and LC_(90) of 139.36 g/L. Petroleum ether fractions of fruits and roots and methanol fraction of fruits showed moderate toxicity against An. stephensi.Conclusions: Astrodaucus persicus is a potential source of valuable and natural larvicidal compounds against malaria vector, An. stephensi and can be used in mosquitoes control programs as an alternative to synthetic insecticides.

Application of Auto-regressive Linear Model in Understanding the Effect of Climate on Malaria Vectors Dynamics in the Three Gorges Reservoir

It is important to understand the dynamics of malaria vectors in implementing malaria control strategies. Six villages were selected from different sections in the Three Gorges Reservoir fc,r exploring the relationship between the climatic ｜：actors and its malaria vector density from 1997 to 2007 using the auto-regressive linear model regressi^n method. The result indicated that both temperature and precipitation were better modeled as quadratic rather than linearly related to the density of Anopheles sinensis.

A Review of Agricultural Pesticides Use and the Selection for Resistance to Insecticides in Malaria Vectors

Most national malaria control programmes rely extensively on pyrethroid insecticides to control mosquito vectors of this disease. Unfortunately, the intensive use of this class of insecticides both in public health and agriculture has led to its reduced efficacy. The objective of this review was to assess the role of agricultural pesticides use on the development of resistance to insecticides in malaria vectors and the potential impact of this resistance on control activities. We searched library catalogues and public databases for studies that included data on resistance to the major classes of insecticides: organochlorines, carbamates, organophosphates and pyrethroids, in the malaria vectors of Anopheles genera. There is a strong geographical bias in published studies many originating from West African countries. Several studies demonstrate that resistance to pyrethroids is widespread in the major malaria vectors of the Anopheles gambiae and Anopheles funestus complexes. Assessing the impact of insecticide resistance on vector control is complicated owing to the lack of studies into the epidemiological consequences of resistance on the control of malaria and other vector borne diseases.

Evaluation of Malaria Transmission and Vector Control Strategies in the Dry Season in the Cotonou V Health Zone, Benin, West Africa

The anarchic urbanization of certain African cities favors the multiplication of the malaria parasite. Thus, the urgent mobilization of African cities is essential to combat this health risk. It is, therefore, with the objective of contributing to the investigation of problem areas that the present study evaluates malaria transmission and vector control strategies in the Cotonou V health zone in particular. This is a cross-sectional study taking into account four neighborhoods, including Wologuèdè, Sainte Rita, Gbèdjromèdé and the area around Etoile Rouge. Two nocturnal captures on voluntary humans and the method of spray were carried out in the dry season from December 2021 to February 2022. On the captured Anopheles, the ELISA Circum-Sporozoite Protein test was performed to determine the infectivity and calculate some transmission parameters. Finally, we conducted a survey using the second stage sampling method with one step to ask selected households about their knowledge of vector control methods, their use and the physical integrity of LLINs. We collected 2386 culicidae of which the majority was Culex quinquefasciatus. After the ELISA test, the 29 Anopheles tested, showed no infectivity, i.e. an EIR of 0 pi/h/n. In addition, 99% of the populations in the Cotonou V area use LLINs to protect themselves. However, coils, door and window screens, aerosol sprays, skin and household repellents, and periodic indoor spraying were used. Finally, the majority of nets observed had T1 tears, but there were also T2, T3 and T4 nets (P-value = 0.0). This study confirms that malaria transmission during the dry season in the Cotonou V health zone is almost negligible but not non-existent. Also, populations are exposed to the nuisance of Culex quinquefasciatus mosquitoes continuously throughout the year.

Larvicidal and repellent potential of Moringa oleifera against malarial vector,Anopheles stephensi Liston(Insecta:Diptera:Culicidae)

Objective:To evaluate the larvicidal and pupicidal potential of the methanolic extracts from Moringa oleifera(M.oleifera) plant seeds against malarial vector Anopheles stephensi(A.stephensi) mosquitoes at different concentrations(20,40,60,80 and 100 ppm).Methods:M.oleifera was collected from the area of around Bharathiar University,Coimbatore.The dried plant materials were powdered by an electrical blender.From each sample,100 g of the plant material were extracted with 300 mL of methanol for 8 h in a Soxhlet apparatus.The extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material(residue) from Arcang amara and Ocimum basilicum,respectively.One gram of the each plant residue was dissolved separately in 100 mL of acetone(stock solution) from which different concentrations, i.e.,20,40,60,80 and 100 ppm were prepared.Results:Larvicidal activity of M.oleifera exhibited in the first to fourth instar larvae of the A.stephensi,and the LC_(50) and LC_(90) values were 57.79 ppm and 125.93 ppm for the first instar,63.90 ppm and 133.07 ppm for the second inslar,72.45 ppm and 139.82 ppm for the third instar,78.93 ppm and 143.20 ppm for the fourth instar,respectively. During the pupal stage the methanolic extract of M.oleifera showed that the LC_(50),and LC_(90) values were 67.77 ppm and 141.00 ppm,respectively.Conclusions:The present study indicates that the phytochemicals derived from M.oleifera seeds extracts are effective mosquito vector control agents and the plant extracts may be used for further integrated pest management programs.

Partial genomic organization of ribosomal protein S7 gene from malaria vector Anopheles stephensi

In this study, we describe the partial genomic organization of ribosomal protein S7 gene isolated from the mosquito Anopheles stephensi. Initially a 558 bp partial cDNA sequence was amplified as precursor mRNA sequence containing 223 bp long intron. 5＇ and 3＇ end sequences were recovered using end specific rapid amplification of cDNA ends （RACE） polymerase chain reaction. The full-length cDNA sequence was 914 nucleotide long with an open reading frame capable of encoding 192 amino acid long protein with calculated molecular mass of 22174 Da and a pI point of 9.94. Protein homology search revealed 〉75% identity to other insect＇s S7 ribosomal proteins. Analysis of sequence alignment revealed several highly conserved domains, one of which is related to nuclear localization signal （NLS） region of human rpS7. Interestingly, intron nucleotide sequence comparison with A. gambiae showed a lesser degree of conservation as compared to coding and untranslated regions. Like this, early studies on the genomic organization and cDNA/ Expressed sequence tag analysis （EST） could help in genome annotation ofA. stephensi, and would be likely to be sequenced in the future.

The Dynamics of Vector-Host Feeding Contact Rate with Saturation: A Case of Malaria in Western Kenya

In this study, we develop an expression for a saturated mosquito feeding rate in an SIS malaria model to determine its effect on infection and transmission dynamics of malaria in the highlands of Western Kenya. The basic reproduction number is established as a sharp threshold that determines whether the disease dies out or persists in the population. Precisely, if , the disease-free equilibrium is globally asymptotically stable and the disease always dies out and if , there exists a unique endemic equilibrium which is globally stable and the disease persists. The contribution of the saturated contact rate to the basic reproduction number and the level of the endemic equilibrium are also analyzed.

Effect of Bendiocarb (Ficam^®80% WP) on Entomological Indices of Malaria Transmission by Indoor Residual Spraying in Burkina Faso, West Africa

Context: The vector control is essential in malaria prevention strategies in several endemic countries in Africa including Burkina Faso. The high transmission of malaria occurs during the period of high vector abundance (August to October) in Burkina Faso. Therefore, a vector control strategy based on the use of indoor residual spraying targeting this period should provide effective protection against malaria. This study aimed to evaluate the effect of bendiocarb applied in indoor residual spraying on entomological parameters of malaria transmission in a pyrethroid resistance area in southwestern, Burkina Faso. Methods: CDC light trap and early morning collections by pyrethrum spray catches were performed monthly to determine the change in entomological parameter within malaria vector in sprayed (Diebougou) and unsprayed sites (Dano). The female’s malaria vectors collected by both methods were used to determine their blood feeding pattern, biting and sporozoites rates as well as the malaria transmission risk estimated by entomological inoculation rate. Results: A total of 26,276 mosquitoes (13,555 anopheline and 12,721 other culicines) were collected using both CDC light trap (9158 mosquitoes) and PSC collection methods (17,118 mosquitoes) from June to December 2012. An. gambiae complex was the predominant species collected. An. gambiae was the predominant species collected (P = 0.0005), comprising 88% of the total collected and the most infected species. Malaria vectors densities were significantly lower in sprayed villages (n = 4303) compared with unsprayed villages (n = 12,569) during post-spraying period (P = 0.0012). In addition, mean human biting rate of An. gambiae s.l. and An. funestus s.l. were significantly lower in sprayed areas compared to unsprayed areas (P < 0.05). Overall, malaria vector transmission risk was significant four-fold lower in villages which received IRS (P = 0.0001) whatever the malaria vectors species (An. gambiae s.l. and An. An. funestus s.l.). Conclusions: The results showed that in the sprayed area (Diebougou), vector densities, human biting rates and malaria transmission risks were very lower than unsprayed areas (Dano). The findings also showed a change in vector behavior especially within An. funestus s.l. which became more zoophagic following IRS. The indoor residual spraying could be promoted as a control tool in areas where malaria transmission occurs during a given period of year.

Case Study for Undetermined Mosquito Species by Polymerase Chain Reaction in Western Burkina Faso

Introduction: Malaria eradication campaigns all over the world are largely based on parasite and vector control. Vector identification, whether morphological or molecular, is an essential component of vector control. This study analyzed the possible causes of indeterminate polymerase chain reaction (PCR) results for mosquito species in Western part of Burkina Faso. Methodology: From July 2021 to November 2021, mosquitoes were collected during the period of high malaria transmission in the village of Séguéré, Houet province, Burkina Faso, and morphologically identified. After DNA extraction, samples were amplified by sine 200× PCR to identify species of the Anopheles gambiae complex. Indeterminate samples were then selected for further analysis. The parameters studied were: DNA dilution, the effect of protocol adjusting, and the type of protocol used. Results: A total of 130 “indeterminate” DNAs diluted 1:10 were analyzed. After dilution, the mean amount was 14.73 ± 3.59 ng/μL and absorbance 1.71 ± 0.1. PCR chain reaction yielded 94.62% (123/130) anopheline species in SINE PCR, 5.38% (7/130) “negative”. A significant difference between SINE PCR before dilution and after dilution was observed (P < 0.001). Identification tests carried out using other protocols gave no positive results. From these results, we note that the adaptation of the protocol significantly reduced the polymerase amplification results of the species. Conclusion: It is therefore necessary to respect the amplification protocols. However, the persistence of “indeterminate” results suggests that further studies should be carried out to shed more light on the subject.

Eradication of malaria through genetic engineering:the current situation

Malaria is an intra-cellular parasitic protozoon responsible for millions of deaths annually.Host and parasite genetic factors are crucial in affecting susceptibility to malaria and progression of the disease.Recent increased deployment of vector controls and new artemisinin combination therapies have dramatically reduced the mortality and morbidity of malaria worldwide.However, the gradual emergence of parasite and mosquito resistance has raised alarm regarding the effectiveness of current artemisinin-based therapies.In this review,mechanisms of anti-malarial drug resistance in the Plasmodium parasite and new genetically engineered tools of research priorities are discussed.The complexity of the parasite lifecycle demands novel interventions to achieve global eradication.However,turning laboratory discovered transgenic interventions into functional products entails multiple experimental phases in addition to ethical and safety hurdles.Uncertainty over the regulatory status and public acceptance further discourage the implementation of genetically modified organisms.

Local climate changes and the spread of malaria in Rwanda

A population’s health makes it possible to draw conclusions about a country’s general development level. In connection with local climatic changes, for example, we can assess how well a society adjusts to the new conditions. To that effect, it has been observed during the last few years that global climate change can also affect human health in various ways. We can differentiate direct health impacts (e.g. extreme weather events, natural catastrophes caused by the weather) from indirect ones. However, the indirect consequences cause by far the greater damages to health. They are being spread increasingly by vectors (mosquitoes, ticks, etc.). Especially when a vector-carried infectious disease (e.g. malaria) migrates into areas where it is not endemic, considerable societal problems can result. The people living there would be immunologically unprepared.

SEIR Model and Simulation for Vector Borne Diseases

An epidemic model is a simplified means of describing the transmission of infectious diseases through individuals. The modeling of infectious diseases is a tool which has been used to study the mechanisms by which diseases spread, to predict the future course of an outbreak and to evaluate strategies to control an epidemic. Epidemic models are of many types. Here, SEIR model is discussed. We first discuss the basics of SEIR model. Then it is applied for vector borne diseases. Steady state conditions are derived. A threshold parameter R0 is defined and is shown that the disease will spread only if its value exceeds 1. We have applied the basic model to one specific diseases-malaria and did the sensitivity analysis too using the data for India. We found sensitivity analysis very important as it told us the most sensitive parameter to be taken care of. This makes the work more of practical use. Numerical simulation is done for vector and host which shows the population dynamics in different compartments.

From control to eradication of malaria:the end of being stuck in second gear?

More than 2 billion people are at risk of malaria,which primarily affects poor populations in tropical and subtropical areas,including Southern Asia.As malaria incidence has been reduced strongly in some parts of endemic regions by combinations of interventions,including artemisinin-based therapies and insecticide-treated bed nets,a new goal has been established recently by charity foundations which support research on malaria:the worldwide eradication of the pathology.Doing away with control approaches which have been applied for the last 50 years and more focus on elimination objectives will deeply change priorities in the area of malaria treatment,chemoprevention,vector control,vaccine research and health system assessment.In this review,actual knowledge on pathogenesis and pharmacology is discussed,and new drugs, vaccines and insecticides are described.

2021年和2022年铜陵市传疟媒介监测分析

目的了解铜陵市传疟媒介种群分布、密度、季节消长及夜间活动等规律,为防治工作提供科学依据。方法2021年和2022年5—10月,采用诱蚊灯全通宵诱蚊法和室外全通宵双层叠帐人诱法开展传疟媒介按蚊监测。结果2021年和2022年铜陵市灯诱法捕获按蚊142只,人诱法捕获按蚊30只,经形态学鉴定均为中华按蚊。2021年、2022年按蚊密度分别为0.1597、0.1690只/(灯·h),鸡棚的按蚊密度两年均保持较高水平,中华按蚊密度高峰期出现在6—7月,中华按蚊夜间捕获高峰时段在4:00—5:00。结论铜陵市中华按蚊分布广泛,存在输入性疟疾传播的风险。

具有蚊子叮咬偏好性的扩散疟疾模型的动力学

为了探讨季节性、蚊子叮咬的偏好性和人类的扩散对疟疾传播的影响,该文提出了一个部分退化的周期反应扩散模型.利用动力系统的持续性理论,研究了模型关于基本再生数R_(0)的阈值动力学.即当R_(0)<1时,疾病灭绝;而当R_(0)>1时,疾病一致持续,且会发生季节性的流行.数值上发现了忽略空间异质性和蚊子叮咬的偏好性会低估疾病传染的风险.

消除疟疾目标后口岸防输入对策探讨

本文概述了中国消除疟疾的主要历程和伟大成就,重点分析了消除疟疾目标后,中国口岸面临的防输入的压力,从建立健全多部门联防联控机制、加强我国卫生检疫技术法规和标准体系建设、强化科技创新、加强人才和物资储备、提升口岸卫生检疫能力、加强来自高危地区的重点人群的主动监测、加强口岸病媒生物的监测能力等方面提出建设性意见,为全国各个口岸开展防止疟疾输入工作提供参考,进一步巩固中国消除疟疾的成果。

海南省部分地区传疟媒介按蚊对4种常用杀虫剂的抗药性测定

目的了解海南省部分地区传疟媒介按蚊对4种常用杀虫剂的抗药性。方法于2008-2010年在多年使用杀虫剂防治疟疾的高疟区昌江县王下乡和东方市江边乡采集媒介按蚊,在昌江县王下乡以人诱法采集大劣按蚊,在东方市江边乡采用牛诱法采集中华按蚊和微小按蚊。取F0代中华按蚊雌蚊、F1代微小按蚊和大劣按蚊雌蚊为测试蚊虫,采用WHO成蚊滤纸接触筒法测定上述测试蚊虫接触4%DDT(1.428g/m2)、0.05%溴氰菊酯(0.0178g/m2)、0.15%氟氯氰菊酯(0.053 4 g/m2)和5%马拉硫磷(1.78 g/m2)等4种杀虫剂的区分剂量60 min内的击倒率,同时设空白对照组。计算半数击倒时间(KT50)和24 h后死亡率,以区分剂量判定抗性级别。结果 DDT、溴氰菊酯和马拉硫磷对大劣按蚊的死亡率均为100%;DDT和溴氰菊酯对大劣按蚊的击倒率分别为82.0%和100%,KT50值分别为46.9 min和18.4 min。DDT、溴氰菊酯、氟氯氰菊酯和马拉硫磷对微小按蚊的死亡率分别为98.1%、99.0%、100%和100%;DDT、溴氰菊酯、氟氯氰菊酯对微小按蚊的击倒率分别为96.3%、99.0%和100%,KT50值分别为31.3 min、16.8 min和7.4 min。DDT、溴氰菊酯和马拉硫磷对中华按蚊的死亡率分别为19.8%、22.9%和43.8%;DDT和溴氰菊酯对中华按蚊的击倒率仅为2.0%,不能测定其KT50。结论本次测试的海南省部分地区的主要传疟媒介大劣按蚊和微小按蚊对常用杀虫剂DDT、溴氰菊酯、马拉硫磷和氟氯氰菊酯等未产生抗药性,而次要媒介中华按蚊对DDT、溴氰菊酯和马拉硫磷有抗药性。

中缅边境(西段)传疟媒介的初步调查

目的了解中缅边境(西段)传疟媒介的分布与构成。方法 2008年8～9月,在中缅边境的中国云南省盈江县及其相邻的缅甸昔懂县6个自然村,用诱蚊灯在人房和牛棚共进行20次通宵诱捕。将捕获的蚊虫以传统方法进行形态学鉴定,然后用复合PCR法鉴别微小按蚊、乌头按蚊和杰普按蚊。同时,抽提部分蚊虫标本总基因组DNA,以巢式PCR方法检测蚊体内的疟原虫感染情况。结果共捕获各类蚊虫4 571只,隶属9属50种,其中按蚊属是优势蚊种,占总量的54.32%(2 483/4 571)。人房和牛棚的按蚊蚊种构成差异有统计学意义,其中人房以腹簇按蚊、微小按蚊和中华按蚊为主,而牛棚以腹簇按蚊(223只)、环纹按蚊(184只)、迷走按蚊(131只)和杰普按蚊(129只)为主。对比有牛村和无牛村中人房的蚊种构成发现,有牛村的人房以微小按蚊(260只)和腹簇按蚊(49只)为主,而无牛村人房则以腹簇按蚊(481只)和中华按蚊(124只)为主。巢式PCR检测1 075只按蚊,其中9只检出疟原虫阳性,分别为微小按蚊(7/408)、乌头按蚊(1/125)和伪威氏按蚊(1/101)。经测序鉴定均为恶性疟原虫感染,目的条带长204 bp。结论中缅边境(西段)蚊虫密度高、种类多,在传疟作用中以微小按蚊最为重要,乌头按蚊和伪威氏按蚊亦为当地的传播媒介。

湖北省1994至2003年疟疾发病与媒介分布

目的 了解传疟媒介在湖北省的分布规律及范围以及与疟疾发病的关系。方法 调查各县 (市 )疟疾发病情况及当地传播媒介种类和分布规律。结果 湖北省疟疾流行的媒介有单纯中华按蚊疟区以及兼有嗜人按蚊疟区 ,通过人血指数调查 ,嗜人按蚊的媒介能量平均高出中华按蚊的 44 .47倍。嗜人按蚊区疟疾发病数占全省发病数的81.3 8%～ 93 .84%。结论 湖北省疟疾近 10年流行主要是在有嗜人按蚊的地区。其特点是发病率高、波动大 ,有些已形成顽固的疫点 ,目前防制重点应放在有嗜人按蚊的地区。