scholarly journals High efficacy of microbial larvicides for malaria vectors control in the city of Yaounde Cameroon following a cluster randomized trial

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christophe Antonio-Nkondjio ◽  
P. Doumbe-Belisse ◽  
L. Djamouko-Djonkam ◽  
C. S. Ngadjeu ◽  
A. Talipouo ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Entomological Inoculation Rate ◽  
Larval Density ◽  
Control Measures ◽  
Rapid Expansion ◽  
Malaria Vectors ◽  
High Efficacy ◽  
Intervention Area ◽  
Breeding Habitats ◽  
The City

AbstractThe rapid expansion of insecticide resistance and outdoor malaria transmission are affecting the efficacy of current malaria control measures. In urban settings, where malaria transmission is focal and breeding habitats are few, fixed and findable, the addition of anti-larval control measures could be efficient for malaria vector control. But field evidences for this approach remains scarce. Here we provide findings of a randomized-control larviciding trial conducted in the city of Yaoundé that support the efficacy of this approach. A two arms random control trial design including 26 clusters of 2 to 4 km2 each (13 clusters in the intervention area and 13 in the non-intervention area) was used to assess larviciding efficacy. The microbial larvicide VectoMax combining Bacillus thuringiensis var israelensis (Bti) and Bacillus sphaericus in a single granule was applied every 2 weeks in all standing water collection points. The anopheline density collected using CDC light traps was used as the primary outcome, secondary outcomes included the entomological inoculation rate, breeding habitats with anopheline larvae, and larval density. Baseline entomological data collection was conducted for 17 months from March 2017 to July 2018 and the intervention lasted 26 months from September 2018 to November 2020. The intervention was associated with a reduction of 68% of adult anopheline biting density and of 79% of the entomological inoculation rate (OR 0.21; 95% CI 0.14–0.30, P < 0.0001). A reduction of 68.27% was recorded for indoor biting anophelines and 57.74% for outdoor biting anophelines. No impact on the composition of anopheline species was recorded. A reduction of over 35% of adult Culex biting densities was recorded. The study indicated high efficacy of larviciding for reducing malaria transmission intensity in the city of Yaoundé. Larviciding could be part of an integrated control approach for controlling malaria vectors and other mosquito species in the urban environment.

scholarly journals High efficacy of microbial larvicides for malaria vectors control in the city of Yaounde Cameroon: a cluster randomised study

2021 ◽  
Author(s):  
Christophe Antonio-Nkondjio ◽  
Patricia Doumbe-Belisse ◽  
Landre Djamouko-Djonkam ◽  
Carmene Sandra Ngadjeu ◽  
Abdou Talipouo ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Entomological Inoculation Rate ◽  
Control Measures ◽  
Rapid Expansion ◽  
Malaria Vectors ◽  
High Efficacy ◽  
Intervention Area ◽  
Breeding Habitats ◽  
Anopheline Larvae ◽  
The City

Abstract The rapid expansion of insecticide resistance and outdoor malaria transmission are affecting the efficacy of current malaria control measures. In urban settings, where malaria transmission is focal and breeding habitats are few, fix and findable, the addition of anti-larval control measures could be efficient for malaria vector control. But field evidences for this approach remains scarce. Here we provide findings of a randomized-control larviciding trial conducted in the city of Yaoundé that support the efficacy of this approach. A two arms random control trial design including 26 clusters of 2 to 4 km2 each (13 clusters in the intervention area and 13 in the non-intervention area) was used to assess larviciding efficacy. The microbial larvicide VectoMax®G combining Bacillus thuringiensis var israelensis (Bti) and Bacillus sphaericus in a single granule was applied twice per month in all standing water collection points. The biting anopheline density collected using CDC light traps was used as the primary outcome, secondary outcomes included the entomological inoculation rate, breeding habitats with anopheline larvae, and larval density. Baseline entomological data collection was conducted for 17 months from March 2017 to July 2018 and the intervention lasted 26 months from September 2018 to November 2020. The intervention was associated with a reduction of over 85% of habitats with anopheline larvae. The application of the larvicide also resulted in a reduction of 68% of adult anopheline biting density and of 79% of the entomological inoculation rate (OR 0.21; 95% CI 0.14–0.30, P < 0.0001). A reduction of 68.27% was recorded for indoor biting anophelines and 57.74% for outdoor biting anophelines. No impact on the composition of anopheline species was recorded. A reduction of over 35% of adult Culex biting densities was recorded. The study also assessed the impact of the microbial larvicide on non-target organisms and registered no significant impact of the larvicide VectoMax on the aquatic microfauna diversity. The study indicated high efficacy of larviciding for reducing malaria transmission intensity in the city of Yaoundé. Larviciding could be part of an integrated control approach for controlling malaria vectors and other mosquito species in the urban environment.

scholarly journals Characterization of Potential Larval Habitats and Spatial Distribution of Anopheles Species Larvae During the Dry Season in Mutare City, Zimbabwe: a Cross-sectional Study

2021 ◽  
Author(s):  
Aramu Makuwaza ◽  
Paddington Tinashe Mundagowa ◽  
Tapiwa Gowera ◽  
Nobert Mudare ◽  
Mukuma Lubinda ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Human Activities ◽  
Rapid Expansion ◽  
Malaria Vectors ◽  
Major Public Health Problem ◽  
Larval Habitats ◽  
Breeding Habitats ◽  
Urban Settlements ◽  
Mosquito Breeding ◽  
The City

Abstract Background: Malaria is traditionally known to be concentrated in rural areas but the disease is increasingly becoming a major public health problem for urban settlements in Africa. National malaria reports show that Mutare City had the greatest endemic malaria burden among all urban settlements in Zimbabwe. To prevent malaria outbreaks, it is essential to monitor malaria vectors in populous urban centers to establish the foci of the vectors while they are still small. This study sought to identify, describe, quantify, geocode mosquito potential larval habitats and their spatial distribution within the city. Methods: Mutare City was divided into four regions and the study was conducted from June to November 2019. Larval sampling of 223 potential habitats was done and the collected larvae were reared until they became adult mosquitoes before being morphologically identified using the keys developed by Gillies and Coetzee. Data were entered and analyzed using Epi Info version 7.2.1.0 statistical package.Results: Anopheline speciation showed that the city was infested with Anopheles funestus (4.9%), An. arabiensis (0.3%), An. pretoriensis (91.3%) An. coustani (0.5%), An. rufipes (2.8%), and An. maculipalpis (0.2%). Overall, An. funestus group was the predominant with An. arabiensis complex less common. The species composition of An. funestus group varied significantly among the sampling habitats. Results showed most mosquito breeding habitats were due to human activities such as agriculture, earth mining, and leaking piped water valves. The digging of shallow wells for domestic use in the high-density areas also contributed to the increase in mosquito breeding habitats.Conclusion: The most significant malaria vectors in the city were An. funestus ss and An. arabiensis. The proliferation of larval habitat hotspots in Mutare City was being fueled by human activities related to earning a living and housing construction. Effective interventions for enhanced larval source management could use a multi-sectoral approach involving all the urban stakeholders. Considering the rapid expansion of the city, more investment is needed to target the most productive habitats by fixing leaking water pipes and frequent application of larvicides with greater residual activity to treat permanent habitats particularly before the rainy season.

scholarly journals A Comprehensive Analysis on Abundance, Distribution, and Bionomics of Potential Malaria Vectors in Mannar District of Sri Lanka

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Nayana Gunathilaka ◽  
Menaka Hapugoda ◽  
Rajitha Wickremasinghe ◽  
Wimaladharma Abeyewickreme
Keyword(s):  
Waste Water ◽  
Sri Lanka ◽  
Current Knowledge ◽  
Breeding Habitat ◽  
Control Measures ◽  
Malaria Vectors ◽  
Detailed Knowledge ◽  
Lagoon Water ◽  
Breeding Habitats ◽  
The Mean

Background. A detailed knowledge of the distribution of the malaria vectors in Mannar district of Sri Lanka has not been studied after 1927. Past records indicated the presence of only seven species of anophelines, namely, An. culicifacies, An. subpictus, An. barbirostris, An. peditaeniatus, An. nigerrimus, An. Jamesii, and An. maculatus. There have been many changes in terms of distribution of Anopheles in the district over time. Methods. Entomological surveillance was conducted on a monthly basis, comprising indoor hand collection, window trap collection, cattle-baited net collection, cattle-baited hut collection, and larval survey from June 2010 to June 2012 in 12 study areas under three entomological sentinel sites. The relationship between seven abiotic variables of the breeding habitats was measured. Pearson’s correlation coefficients were used to determine the associations between climatic variables and anopheline densities. Results. A total of 74,181 mosquitoes belonging to 14 Anopheles species were recorded. An. subpictus was the most predominant species from all techniques representing 92% (n=68,268) of the total anopheline collection. However, Anopheles culicifacies was not recorded from any site during the study period. Larval surveys identified 12 breeding habitat categories including waste water collections, lagoon water collections, and drains which were not recorded as breeding habitats by previous studies. The mean dissolved oxygen level of waste water collections was 3.45±0.15 mg/l. The mean salinity and conductivity of lagoon water collections were 21105±1344 mg/l and 34734±1974 μs/cm, respectively. Conclusion. The present study provides the updated knowledge on anopheline distribution and vector bionomics. Therefore, documentation of the current knowledge would be useful for learners and health authorities to design appropriate vector control measures in the prevention of reintroduction of malaria.

scholarly journals Genetic diversity of Anopheles coustani in high malaria transmission foci in southern and central Africa

2020 ◽  
Author(s):  
Ilinca I. Ciubotariu ◽  
Christine M. Jones ◽  
Tamaki Kobayashi ◽  
Thierry Bobanga ◽  
Mbanga Muleba ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Malaria Transmission ◽  
Malaria Parasite ◽  
Indoor Residual Spraying ◽  
Control Measures ◽  
Sub Saharan Africa ◽  
Health Concern ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Internal Transcribed Spacer Region

AbstractDespite ongoing malaria control efforts implemented throughout sub-Saharan Africa, malaria remains an enormous public health concern. Current interventions such as indoor residual spraying with insecticides and use of insecticide-treated bed nets are aimed at targeting the key malaria vectors that are primarily endophagic and endophilic. While these control measures have resulted in a substantial decline in malaria cases and continue to impact indoor transmission, the importance of alternative vectors for malaria transmission has been largely neglected. Anopheles coustani, an understudied vector of malaria, is a species previously thought to exhibit mostly zoophilic behavior. However, recent studies from across Africa bring to light the contribution of this and ecologically similar anopheline species to human malaria transmission. Like many of these understudied species, An. coustani has greater anthropophilic tendencies than previously appreciated, is often both endophagic and exophagic, and carries Plasmodium falciparum sporozoites. These recent developments highlight the need for more studies throughout the geographic range of this species and the potential need to control this vector. The aim of this study was to explore the genetic variation of An. coustani mosquitoes and the potential of this Anopheles species to contribute to malaria parasite transmission in high transmission settings in Nchelenge District, Zambia, and the Kashobwe and Kilwa Health Zones in Haut-Katanga Province, the Democratic Republic of the Congo (DRC). Morphologically identified An. coustani specimens that were trapped outdoors in these study sites were analyzed by PCR and sequencing for species identification and blood meal sources, and malaria parasite infection was determined by ELISA and qPCR. Fifty specimens were confirmed to be An. coustani by the analysis of mitochondrial DNA cytochrome c oxidase subunit I (COI) and ribosomal internal transcribed spacer region 2 (ITS2). Further, maximum likelihood phylogenetic analysis of COI and ITS2 sequences revealed two distinct phylogenetic groups within this relatively small regional collection. Our findings indicate that both An. coustani groups have anthropophilic and exophagic habits and come into frequent contact with P. falciparum, suggesting that this potential alternative malaria vector might elude current vector controls in Northern Zambia and Southern DRC. This study sets the groundwork for more thorough investigations of bionomic characteristics and genetic diversity of An. coustani and its contribution to malaria transmission in these regions.

scholarly journals High malaria transmission sustained by Anopheles gambiae s.l. occurring both indoors and outdoors in the city of Yaoundé, Cameroon

2018 ◽  
Vol 3 ◽  
pp. 164 ◽  
Author(s):  
Patricia Doumbe-Belisse ◽  
Carmene Sandra Ngadjeu ◽  
Nadege Sonhafouo-Chiana ◽  
Abdou Talipouo ◽  
Landre Djamouko-Djonkam ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Public Health Problem ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Major Public Health Problem ◽  
Infection Status ◽  
Mosquito Abundance ◽  
Biting Rate ◽  
The City

Background: Malaria remains a major public health problem in Cameroon; however, despite reports on the adaptation of anopheline species to urban habitats, there is still not enough information on malaria transmission pattern in urban settings. In the frame of a larval control trial in the city of Yaoundé, we conducted baseline surveys to assess malaria transmission dynamics in this city. Methods: Adult mosquitoes were collected indoors and outdoors using CDC light traps and human landing catches from March 2017 to March 2018 in 30 districts of Yaoundé, Cameroon. Mosquitoes were sorted by genus and identified to the species level using PCR. The TaqMan method and ELISA were used to determine mosquito infection status to Plasmodium. Bioassays were conducted to assess female Anopheles gambiae susceptibility to insecticides. Results: A total of 218,991 mosquitoes were collected. The main malaria vectors were An. gambiae s.l. (n=6154) and An. funestus s.l. (n=229). Of the 1476 An. gambiae s.l. processed by PCR, 92.19% were An. coluzzii and 7.81% An. gambiae. An. funestus s.l. was composed of 93.01% (173/186) An. funestus and 4.84% (13/186) An. leesoni. The average biting rate of anopheline was significantly high outdoor than indoor (P=0.013). Seasonal variation in mosquito abundance and biting rate was recorded. The infection rate by Plasmodium falciparum was 2.13% (104/4893 mosquitoes processed). The annual entomological inoculation rate was found to vary from 0 to 92 infective bites/man/year (ib/m/y). Malaria transmission risk was high outdoor (66.65 ib/m/y) compared to indoor (31.14 ib/m/y). An. gambiae s.l. was found highly resistant to DDT, permethrin and deltamethrin. High prevalence of the West Africa kdr allele 1014F was recorded and this was not found to influence An. gambiae s.l. infection status.   Conclusion: The study suggests high malaria transmission occurring in the city of Yaoundé and call for immediate actions to improve control strategies.

Influence of climatic factors on aggression and infectivity of Anopheles in the districts the Indoor Residual Spray (IRS) in Northern Benin, West Africa.

2019 ◽  
Author(s):  
André SOMINAHOUIN ◽  
Germain Gil Padonou ◽  
Rodrigue Landéhou ◽  
Albert Sourou Salako ◽  
Hermann Sagbohan ◽  
...  
Keyword(s):  
Wind Speed ◽  
Vector Control ◽  
Malaria Transmission ◽  
Climatic Factors ◽  
Control Strategies ◽  
Meteorological Data ◽  
Blood Feeding ◽  
Control Measures ◽  
Malaria Vectors ◽  
Significant Difference

Abstract Background: Climate variability influence the diversity and abundance of malaria vectors and thereby on malaria transmission dynamics. Examine its effect on Anopheles parameters involved in transmission may predict the potential malaria hotspot as a right target for its control intervention strategies. Here, we investigated the influence of meteorological parameters on the aggressiveness and infectivity of Anopheles in two health districts zones where IRS has been extended in Northern Benin. Methods: Mosquito collections were carried out using human landing catches to evaluate rates of aggression and infectivity in twelve villages. Concomitantly, meteorological data from synoptic stations of Benin and neighbouring countries were collected in 2016-2017. Results: The spatial distribution of infective bites of An. gambiae is characterized by an intense aggression in the rural villages of the study area. Analysis of variances showed significant HBR difference according to the period but not according to the locality. However, the same analysis carried out with the infectivity rate shows no significant difference according to the period and the locality. In addition, the number of infective bites per man per month is higher in August and October, and the climatic parameters that have mainly favoured aggression are wind speed, humidity, sunshine and temperature. Indeed, the peak of wind speed is concentrated around 1.2 km / h and in September (5 km / h) whereas the aggressiveness score of Anopheles in the region is greater than 10 infective bites per man a year. Conclusion Malaria transmission by Anopheles is influenced by climatic factors. The climate observed in the districts where IRS was extended in northern Benin has a real impact on Anopheles density and weakens current and future vector control strategies. This could lead to a series of modifications observed in anopheline populations just after IRS implementation ranging from a tendency to exophagy, from a decrease in the rate of blood-feeding to changes in the time, and change in aggressiveness. These phenomena most likely contribute to the sustainability of malaria transmission despite vector control measures. Keywords: Infectivity, aggression, Climate, Anopheles gambiae ( s.l. ), IRS, Benin.

scholarly journals Biologically meaningful coverage indicators for eliminating malaria transmission

2012 ◽  
Vol 8 (5) ◽  
pp. 874-877 ◽  
Author(s):  
Samson S. Kiware ◽  
Nakul Chitnis ◽  
Gregor J. Devine ◽  
Sarah J. Moore ◽  
Silas Majambere ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Human Exposure ◽  
Optimal Strategies ◽  
Control Measures ◽  
Malaria Vectors ◽  
Two Dimensional ◽  
Front Line ◽  
High Coverage ◽  
Long Lasting Insecticidal Nets ◽  
Blood Meals

Mosquitoes, which evade contact with long-lasting insecticidal nets and indoor residual sprays, by feeding outdoors or upon animals, are primary malaria vectors in many tropical countries. They can also dominate residual transmission where high coverage of these front-line vector control measures is achieved. Complementary strategies, which extend insecticide coverage beyond houses and humans, are required to eliminate malaria transmission in most settings. The overwhelming diversity of the world's malaria transmission systems and optimal strategies for controlling them can be simply conceptualized and mapped across two-dimensional scenario space defined by the proportion of blood meals that vectors obtain from humans and the proportion of human exposure to them which occurs indoors.

Challenging the Terms of Order: Representations of the Detroit Rebellions, 1967–1968

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Jordan T. Camp
Keyword(s):  
State Violence ◽  
Rapid Expansion ◽  
Capitalist Development ◽  
Civil Structures ◽  
Us History ◽  
Political Struggles ◽  
Stuart Hall ◽  
The Relationship ◽  
The City ◽  
John Clarke

While many analysts have commented on the representation of 1968 campus events and antiwar demonstrations, less attention has been paid to the global significance of the dramatic struggles in industrial Detroit during the period. The meanings of events in the city were intensely fought over. As Stuart Hall, Chas Critcher, Tony Jefferson, John Clarke, and Brian Roberts observed, the events of 1968 were “an act of collective will, the breaks and ruptures stemming from the rapid expansion in the ideology, culture and civil structures of the new capitalism . . . in the form of a ‘crisis of authority.’” In Detroit the crisis of authority was expressed in the form of popular political struggles against racism, state violence, and the contradictions of life in the industrial capitalist city. This article asks and answers the following research questions about the struggle over the meaning of this decisive turning point in US history: What was the relationship between racial ordering, uneven capitalist development, and mass antiracist and class struggles? How did Black working-class organic intellectuals resist and alter hegemonic definitions of the situation? How are the dialectics of insurgency and counterinsurgency to be best theorized during this precise historical conjuncture? 

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