scholarly journals Effect of wall type, delayed mortality and mosquito age on the residual efficacy of a clothianidin-based indoor residual spray formulation (SumiShield™ 50WG) in southern Mozambique

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0248604
Author(s):  
Helena Marti-Soler ◽  
Mara Máquina ◽  
Mercy Opiyo ◽  
Celso Alafo ◽  
Ellie Sherrard-Smith ◽  
...  
Keyword(s):  
Vector Control ◽  
Disease Transmission ◽  
Indoor Residual Spraying ◽  
World Health ◽  
Malaria Vector Control ◽  
Mosquito Vector ◽  
Post Exposure ◽  
Mosquito Mortality ◽  
Residual Efficacy ◽  
Delayed Mortality

Indoor residual spraying (IRS) is one of the main malaria vector control strategies in Mozambique alongside the distribution of insecticide treated nets. As part of the national insecticide resistance management strategy, Mozambique introduced SumiShield™ 50WG, a third generation IRS product, in 2018. Its residual efficacy was assessed in southern Mozambique during the 2018–2019 malaria season. Using a susceptible Anopheles arabiensis strain, residual efficacy was assessed on two different wall surfaces, cement and mud-plastered walls, using standard WHO (World Health Organization) cone bioassay tests at three different heights. Female mosquitoes of two age groups (2–5 and 13–26 day old) were exposed for 30 minutes, after which mortality was observed 24h, 48h, 72h, and 96h and 120h post-exposure to assess (delayed) mortality. Lethal times (LT) 90, LT50 and LT10 were estimated using Bayesian models. Mortality 24h post exposure was consistently below 80%, the current WHO threshold value for effective IRS, in both young and old mosquitoes, regardless of wall surface type. Considering delayed mortality, residual efficacies (mosquito mortality equal or greater than 80%) ranged from 1.5 to ≥12.5 months, with the duration depending on mortality time post exposure, wall type and mosquito age. Looking at mortality 72h after exposure, residual efficacy was between 6.5 and 9.5 months, depending on wall type and mosquito age. The LT50 and LT10 (i.e. 90% of the mosquitoes survive exposure to the insecticides) values were consistently higher for older mosquitoes (except for LT10 values for 48h and 72h post-exposure mortality) and ranged from 0.9 to 5.8 months and 0.2 to 7.8 months for LT50 and LT10, respectively. The present study highlights the need for assessing mosquito mortality beyond the currently recommended 24h post exposure. Failure to do so may lead to underestimation of the residual efficacy of IRS products, as delayed mortality will lead to a further reduction in mosquito vector populations and potentially negatively impact disease transmission. Monitoring residual efficacy on relevant wall surfaces, including old mosquitoes that are ultimately responsible for malaria transmission, and assessing delayed mortalities are critical to provide accurate and actionable data to guide vector control programmes.

scholarly journals Effect of wall type, delayed mortality and mosquito age on the residual efficacy of a clothianidin-based indoor residual spray formulation (SumiShield™ 50WG) in southern Mozambique

2021 ◽  
Author(s):  
Helena Marti-Soler ◽  
Mara Maquina ◽  
Mercy Opiyo ◽  
Celso Alafo ◽  
Ellie Sherrard-Smith ◽  
...  
Keyword(s):  
Vector Control ◽  
Disease Transmission ◽  
Indoor Residual Spraying ◽  
World Health ◽  
Malaria Vector Control ◽  
Mosquito Vector ◽  
Post Exposure ◽  
Mosquito Mortality ◽  
Residual Efficacy ◽  
Delayed Mortality

AbstractBackgroundIndoor residual spraying (IRS) is one of the main malaria vector control strategies in Mozambique alongside the distribution of insecticide treated nets. As part of the national insecticide resistance management strategy, Mozambique introduced SumiShield™ 50WG, a third generation IRS product, in 2018. Its residual efficacy was assessed in southern Mozambique during the 2018-2019 malaria season.MethodsTwo different wall surfaces, cement and mud-plastered surfaces, daily mosquito mortality up to 120 hours post-exposure, and older mosquitoes (13-26d old) were included in standard WHO (World Health Organization) cone bioassay tests. Lethal times (LT) 90, LT50 and LT10 were estimated using Bayesian models.ResultsMortality 24h post exposure was consistently below 80%, the current WHO threshold value for effective IRS, in both young and old mosquitoes, regardless of wall surface type. Considering delayed mortality, residual efficacies (mosquito mortality equal or greater than 80%) ranged from 1 to ≥12 months, with the duration depending on mortality time post exposure, wall type and mosquito age. Looking at mortality 72h after exposure, residual efficacy was between 6 and 9 months, depending on wall type and mosquito age. Mortality of older mosquitoes was significantly higher on mud-surfaces compared to cemented-surfaces 24h post exposure, but this difference was not significant for the delayed mortalities. The LT50 and LT10 (i.e. 90% of the mosquitoes survive exposure to the insecticides) values were consistently higher for older mosquitoes using the 24h post-exposure observations and ranged from 0.2 to 5.7 months and 0.2 to 7.2 months for LT50 and LT10, respectively.ConclusionsThe present study highlights the need for assessing mosquito mortality beyond the currently recommended 24h post exposure. Failure to do so may lead to underestimation of the residual efficacy of IRS products, as delayed mortality will lead to a further reduction in mosquito vector populations and potentially negatively impact disease transmission. Monitoring residual efficacy on relevant wall surfaces, including old mosquitoes that are ultimately responsible for malaria transmission, and assessing delayed mortalities are critical to provide accurate and actionable data to guide vector control programmes.

scholarly journals Quantifying and characterizing hourly human exposure to malaria vectors bites in rural southwest Burkina Faso

2019 ◽  
Author(s):  
D.D Soma ◽  
B Zogo ◽  
P Taconet ◽  
A Somé ◽  
S Coulibaly ◽  
...  
Keyword(s):  
Burkina Faso ◽  
Vector Control ◽  
Rural Area ◽  
Malaria Vector ◽  
Human Exposure ◽  
Protective Efficacy ◽  
Indoor Residual Spraying ◽  
World Health ◽  
Malaria Vectors ◽  
Malaria Vector Control

AbstractBackgroundTo sustain the efficacy of malaria vector control, the World Health Organization (WHO) recommends the combination of effective tools. Before designing and implementing additional strategies in any setting, it is critical to monitor or predict when and where transmission occurs. However, to date, very few studies have quantified the behavioural interactions between humans and Anopheles vectors. Here, we characterized residual transmission in a rural area of Burkina Faso where long lasting insecticidal nets (LLIN) are widely used.MethodsWe analysed data on both human and malaria vectors behaviours from 27 villages to measure hourly human exposure to vector bites in dry and rainy seasons using mathematical models. We estimated the protective efficacy of LLINs and characterised where (indoors vs. outdoors) and when both LLIN users and non-users were exposed to vector bites.ResultsThe percentage of the population who declared sleeping under a LLIN the previous night was very high regardless of the season, with an average LLIN use ranging from 92.43% to 99.89%. The use of LLIN provided > 80% protection against exposure to vector bites. The proportion of exposure for LLIN users was 29-57% after 05:00 and 0.05-12 % before 20:00. More than 80% of exposure occurred indoors for LLIN users and the estimate reached 90% for children under five years old in the dry cold season.ConclusionsThis study supports the current use of LLIN as a primary malaria vector control tool. It also emphasises the need to complement LLIN with indoor-implemented measures such as indoor residual spraying (IRS) and/or house improvement to effectively combat malaria in the rural area of Diébougou. Furthermore, malaria elimination programmes would also require strategies that target outdoor biting vectors to be successful in the area.

Susceptibility of Anopheles gambiae complex to carbamates and organophosphate insecticides in Uyo, Akwa Ibom State, Nigeria

2020 ◽  
Vol 41 (1) ◽  
pp. 114-118
Author(s):  
N.I. Udoidung ◽  
K.N. Opara ◽  
P.D. Okodi ◽  
N.D. Ekpo ◽  
I. Atting
Keyword(s):  
Vector Control ◽  
Anopheles Gambiae ◽  
Malaria Vector ◽  
Control Strategies ◽  
Sub Saharan Africa ◽  
World Health ◽  
Malaria Vector Control ◽  
Insecticide Susceptibility ◽  
Post Exposure ◽  
Organophosphate Insecticides

Rapid emergence in insecticide resistance among malaria vector populations to commonly used public health insecticides poses a challenge to current malaria vector control strategies and interventions in sub- Saharan Africa. This study was conducted to determine the susceptibility status of female An.gambiae s.l to Propoxur (0.01%) and bendiocarb (0.1%) (carbamate) and pirimiphosmethyl (0.25%) (organophosphate) insecticides in Uyo Metropolis, Akwa Ibom State, Nigeria. The larvae of An. gambiae s.l were collected from natural water bodies and other potential breeding sites from different sites in Uyo Metropolis. Insecticide susceptibility bioassays were performed according to the World Health Organization standard operating procedures on 2-3 days old, sugar-fed but none blood fed female Anopheles mosquitoes. Post exposure mortality after 24 hours and knockdown values for KDT50 and KDT95 were calculated. Knock-down at 1 hour insecticide exposure ranged from 94 % to 100 %. Mortality after 24 hours post exposure was 100% for all insecticides except Propoxur which was 98 %. There was high variability in KDT50 and KDT95 values (in minutes) with propoxur (4.337 and 15.620), Bendiocarb (9.523 and 20.996) and pirimiphosmethyl (39.908 and 61.722) respectively. Adopting the WHO criteria, the mosquitoes were not resistant to any of the insecticides tested. The results therefore showed that vector control campaigns employing the use of any of these insecticides in the study area would not be compromised. However, there is need for continued monitoring to ensure early detection of resistance. Keywords: Anopheles gambiae; insecticide susceptibility; Uyo; Akwa Ibom State; Nigeria.

scholarly journals Ivermectin as an endectocide may boost control of malaria vectors in India and contribute to elimination

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Sundus Shafat Ahmad ◽  
Manju Rahi ◽  
Poonam Saroha ◽  
Amit Sharma
Keyword(s):  
Vector Control ◽  
Malaria Elimination ◽  
Control Strategies ◽  
Mosquito Species ◽  
Indoor Residual Spraying ◽  
World Health ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Malaria Vector Control ◽  
Indian Government

AbstractMalaria constitutes one of the largest public health burdens faced by humanity. Malaria control has to be an efficient balance between diagnosis, treatment and vector control strategies. The World Health Organization currently recommends indoor residual spraying and impregnated bed nets as two malaria vector control methods that have shown robust and persistent results against endophilic and anthropophilic mosquito species. The Indian government launched the National Framework for Malaria Elimination in 2016 with the aim to achieve the elimination of malaria in a phased and strategic manner and to sustain a nation-wide malaria-free status by 2030. India is currently in a crucial phase of malaria elimination and novel vector control strategies maybe helpful in dealing with various challenges, such as vector behavioural adaptations and increasing insecticide resistance among the Anopheles populations of India. Ivermectin can be one such new tool as it is the first endectocide to be approved in both animals and humans. Trials of ivermectin have been conducted in endemic areas of Africa with promising results. In this review, we assess available data on ivermectin as an endectocide and propose that this endectocide should be explored as a vector control tool for malaria in India. Graphical Abstract

scholarly journals Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Henry Ddumba Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. This study examined the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18–0.65, p = 0.001), but not Anopheles gambiae sensu stricto (s.s.) nor Anopheles arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49–0.94, p = 0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002–0.009, p < 0.001), and An. funestus sensu lato (s.l.) (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005–0.004, p < 0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07–0.33, p < 0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviourally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

scholarly journals Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria

2020 ◽  
Vol 376 (1818) ◽  
pp. 20190817 ◽  
Author(s):  
Joel Hellewell ◽  
Ellie Sherrard-Smith ◽  
Sheila Ogoma ◽  
Thomas S. Churcher
Keyword(s):  
Disease Transmission ◽  
Pyrethroid Resistance ◽  
Control Strategies ◽  
Indoor Residual Spraying ◽  
Additional Benefit ◽  
Sub Saharan Africa ◽  
Outdoor Biting ◽  
Mosquito Mortality ◽  
The Impact ◽  
Long Lasting Insecticidal Nets

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.

scholarly journals Residual and Fumigant Effects of Bendiocarb WP80 in a Malarious Areas in Borderline of Iran and Pakistan  

2021 ◽  
Author(s):  
Mohammad Reza Abai ◽  
Hassan Vatandoost ◽  
Hossein Dorzadeh ◽  
Mansoreh Shayeghi ◽  
Ahmad Ali Hanafi-bojd ◽  
...  
Keyword(s):  
Vector Control ◽  
Anopheles Stephensi ◽  
Indoor Residual Spraying ◽  
Residual Effect ◽  
Malaria Vector Control ◽  
Biological Assays ◽  
The Public ◽  
Main Activity ◽  
Contact Bioassay ◽  
Old Females

Abstract Background: Malaria and leishmaniasis are the public health problems in southern Iran. The main activity of vector control is indoor residual spraying using pyrethrpids. The aim of study was to evaluate the biological assays of bendiocarb WP at different surfaces of wall. Materials and Methods: The residual effect of bendicocarb WP80 at 400 mg/m2 was evauated on various local surfaces of rooms such as mud and plaster as well as thatch roofs and wooden. WHO standard cones using contact bioassays were carried out using laboratory reared sugar-fed, 48-72 h old females of Anopheles stephensi . Contact bioassays were carried out on sprayed surfaces for 150 days.Results: Contact bioassay on surfaces treated with bendicocarb WP80 diffferent surfaces was estimated about 2 months. Fumigant tests of bendicocarb WP80 at 400 mg/m2 revealed 50-93.83% mortality with one month persistency.Discussion: The rsults hsowed that carbamte insecticide could be used as rotation with pyrethroids for malaria vector control .

scholarly journals Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors: a cost-effective supplement for malaria interventions

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Guofa Zhou ◽  
Eugenia Lo ◽  
Andrew K. Githeko ◽  
Yaw A. Afrane ◽  
Guiyun Yan
Keyword(s):  
Cost Effectiveness ◽  
Vector Control ◽  
Malaria Vector ◽  
Indoor Residual Spraying ◽  
Cost Effective ◽  
Control Measures ◽  
Malaria Vector Control ◽  
Potential Cost ◽  
Outdoor Transmission ◽  
Indoor And Outdoor

AbstractThe issues of pyrethroid resistance and outdoor malaria parasite transmission have prompted the WHO to call for the development and adoption of viable alternative vector control methods. Larval source management is one of the core malaria vector interventions recommended by the Ministry of Health in many African countries, but it is rarely implemented due to concerns on its cost-effectiveness. New long-lasting microbial larvicide can be a promising cost-effective supplement to current vector control and elimination methods because microbial larvicide uses killing mechanisms different from pyrethroids and other chemical insecticides. It has been shown to be effective in reducing the overall vector abundance and thus both indoor and outdoor transmission. In our opinion, the long-lasting formulation can potentially reduce the cost of larvicide field application, and should be evaluated for its cost-effectiveness, resistance development, and impact on non-target organisms when integrating with other malaria vector control measures. In this opinion, we highlight that long-lasting microbial larvicide can be a potential cost-effective product that complements current front-line long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) programs for malaria control and elimination. Microbial larviciding targets immature mosquitoes, reduces both indoor and outdoor transmission and is not affected by vector resistance to synthetic insecticides. This control method is a shift from the conventional LLINs and IRS programs that mainly target indoor-biting and resting adult mosquitoes.

scholarly journals Using Gene Drive Technologies to Control Vector-Borne Infectious Diseases

2018 ◽  
Vol 10 (12) ◽  
pp. 4789 ◽  
Author(s):  
Stephanie James ◽  
Karen Tountas
Keyword(s):  
Disease Transmission ◽  
Sub Saharan Africa ◽  
Reproductive Capacity ◽  
World Health ◽  
Mosquito Vector ◽  
Gene Drive ◽  
African Region ◽  
Safety Testing ◽  
Malaria Burden ◽  
Health Organization

After years of success in reducing the global malaria burden, the World Health Organization (WHO) recently reported that progress has stalled. Over 90% of malaria deaths world-wide occurred in the WHO African Region. New tools are needed to regain momentum and further decrease the burden of malaria. Gene drive, an emerging technology that can enhance the inheritance of beneficial genes, offers potentially transformative solutions for overcoming these challenges. Gene drives may decrease disease transmission by interfering with the growth of the malaria parasite in the mosquito vector or reducing mosquito reproductive capacity. Like other emerging technologies, development of gene drive products faces technical and non-technical challenges and uncertainties. In 2018, to begin addressing such challenges, a multidisciplinary group of international experts published comprehensive recommendations for responsible testing and implementation of gene drive-modified mosquitoes to combat malaria in Sub-Saharan Africa. Considering requirements for containment, efficacy and safety testing, monitoring, stakeholder engagement and authorization, as well as policy and regulatory issues, the group concluded that gene drive products for malaria can be tested safely and ethically, but that this will require substantial coordination, planning, and capacity development. The group emphasized the importance of co-development and co-ownership of products by in-country scientists.

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