scholarly journals Which indoor residual spraying insecticide best complements standard pyrethroid long-lasting insecticidal nets for improved control of pyrethroid resistant malaria vectors?

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245804
Author(s):  
Thomas Syme ◽  
Augustin Fongnikin ◽  
Damien Todjinou ◽  
Renaud Govoetchan ◽  
Martial Gbegbo ◽  
...  
Keyword(s):  
Vector Control ◽  
Mosquito Control ◽  
Indoor Residual Spraying ◽  
Residual Effect ◽  
Blood Feeding ◽  
Additive Effect ◽  
Malaria Vectors ◽  
Vector Population ◽  
Pirimiphos Methyl ◽  
The Impact

Background Where resources are available, non-pyrethroid IRS can be deployed to complement standard pyrethroid LLINs with the aim of achieving improved vector control and managing insecticide resistance. The impact of the combination may however depend on the type of IRS insecticide deployed. Studies comparing combinations of pyrethroid LLINs with different types of non-pyrethroid IRS products will be necessary for decision making. Methods The efficacy of combining a standard pyrethroid LLIN (DuraNet®) with IRS insecticides from three chemical classes (bendiocarb, chlorfenapyr and pirimiphos-methyl CS) was evaluated in an experimental hut trial against wild pyrethroid-resistant Anopheles gambiae s.l. in Cové, Benin. The combinations were also compared to each intervention alone. WHO cylinder and CDC bottle bioassays were performed to assess susceptibility of the local An. gambiae s.l. vector population at the Cové hut site to insecticides used in the combinations. Results Susceptibility bioassays revealed that the vector population at Cové, was resistant to pyrethroids (<20% mortality) but susceptible to carbamates, chlorfenapyr and organophosphates (≥98% mortality). Mortality of wild free-flying pyrethroid resistant An. gambiae s.l. entering the hut with the untreated net control (4%) did not differ significantly from DuraNet® alone (8%, p = 0.169). Pirimiphos-methyl CS IRS induced the highest mortality both on its own (85%) and in combination with DuraNet® (81%). Mortality with the DuraNet® + chlorfenapyr IRS combination was significantly higher than each intervention alone (46% vs. 33% and 8%, p<0.05) demonstrating an additive effect. The DuraNet® + bendiocarb IRS combination induced significantly lower mortality compared to the other combinations (32%, p<0.05). Blood-feeding inhibition was very low with the IRS treatments alone (3–5%) but increased significantly when they were combined with DuraNet® (61% - 71%, p<0.05). Blood-feeding rates in the combinations were similar to the net alone. Adding bendiocarb IRS to DuraNet® induced significantly lower levels of mosquito feeding compared to adding chlorfenapyr IRS (28% vs. 37%, p = 0.015). Conclusions Adding non-pyrethroid IRS to standard pyrethroid-only LLINs against a pyrethroid-resistant vector population which is susceptible to the IRS insecticide, can provide higher levels of vector mosquito control compared to the pyrethroid net alone or IRS alone. Adding pirimiphos-methyl CS IRS may provide substantial improvements in vector control while adding chlorfenapyr IRS can demonstrate an additive effect relative to both interventions alone. Adding bendiocarb IRS may show limited enhancements in vector control owing to its short residual effect.

scholarly journals Can pyrethroid-piperonyl butoxide (PBO) nets reduce the efficacy of indoor residual spraying with pirimiphos-methyl against pyrethroid-resistant malaria vectors?

2021 ◽  
Author(s):  
Thomas Syme ◽  
Martial Gbegbo ◽  
Dorothy Obuobi ◽  
Augustin Fongnikin ◽  
Abel Agbevo ◽  
...  
Keyword(s):  
Indoor Residual Spraying ◽  
Blood Feeding ◽  
Antagonistic Effect ◽  
Malaria Vectors ◽  
Cytochrome P450 Enzymes ◽  
Vector Population ◽  
Mosquito Mortality ◽  
Pirimiphos Methyl ◽  
The Impact ◽  
Permanet 3.0

As the uptake of pyrethroid-PBO ITNs increases, their combination with IRS insecticides could become an operational reality in many malaria-endemic communities. Pirimiphos-methyl is a pro-insecticide requiring activation by mosquito cytochrome P450 enzymes to induce toxicity while PBO blocks activation of these enzymes in pyrethroid-resistant vector mosquitoes. PBO may thus antagonise the toxicity of pirimiphos-methyl IRS when combined with pyrethroid-PBO ITNs. The impact of combining two major brands of pyrethroid-PBO ITNs (Olyset Plus, PermaNet 3.0) with pirimiphos-methyl IRS (Actellic 300CS) was evaluated against pyrethroid-resistant Anopheles gambiae sl in two parallel experimental hut trials in southern Benin in comparison to bendiocarb IRS and each intervention alone. The wild vector population was resistant to pyrethroids but susceptible to pirimiphos-methyl and bendiocarb. PBO pre-exposure partially restored deltamethrin toxicity but not permethrin. Mosquito mortality in experimental huts was significantly improved in the combinations of bendiocarb IRS with Olyset Plus (33%) and PermaNet 3.0 (38%) compared to bendiocarb IRS alone (14 to 16%, p<0.001), demonstrating an additive effect. Conversely, mortality was significantly reduced in the combinations of pirimiphos-methyl IRS with Olyset Plus (59%) and PermaNet 3.0 (55%) compared to pirimiphos-methyl IRS alone (77 to 78%, p<0.001), demonstrating an antagonistic effect. Combining pirimiphos-methyl IRS with the pyrethroid-PBO ITNs provided significantly improved mosquito mortality (55 to 59%) compared to the pyrethroid-PBO ITNs alone (22 to 26%) and improved blood-feeding inhibition relative to the IRS alone. This study provided evidence of an antagonistic effect when pyrethroid-PBO ITNs were combined with pirimiphos-methyl IRS in the same household resulting in lower levels of vector mosquito mortality compared to the IRS alone. Pirimiphos-methyl IRS also showed potential to significantly enhance malaria control when deployed to complement pyrethroid-PBO ITNs in an area where PBO fails to fully restore susceptibility to pyrethroids.

scholarly journals Reduced exposure to malaria vectors following indoor residual spraying of pirimiphos-methyl in a high-burden district of rural Mozambique with high ownership of long-lasting insecticidal nets: entomological surveillance results from a cluster-randomized trial

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Joseph M. Wagman ◽  
Kenyssony Varela ◽  
Rose Zulliger ◽  
Abuchahama Saifodine ◽  
Rodaly Muthoni ◽  
...  
Keyword(s):  
Controlled Trial ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Light Traps ◽  
High Burden ◽  
Randomized Controlled ◽  
Pirimiphos Methyl ◽  
Cluster Randomized ◽  
The Impact ◽  
Long Lasting Insecticidal Nets

Abstract Background The need to develop new products and novel approaches for malaria vector control is recognized as a global health priority. One approach to meeting this need has been the development of new products for indoor residual spraying (IRS) with novel active ingredients for public health. While initial results showing the impact of several of these next-generation IRS products have been encouraging, questions remain about how to best deploy them for maximum impact. To help address these questions, a 2-year cluster-randomized controlled trial to measure the impact of IRS with a microencapsulated formulation of pirimiphos-methyl (PM) in an area with high ownership of long-lasting insecticidal nets (LLINs) was conducted in a high-transmission district of central Mozambique with pyrethroid resistant vectors. Presented here are the results of the vector surveillance component of the trial. Methods The 2 year, two-armed trial was conducted in Mopeia District, Zambezia Province, Mozambique. In ten sentinel villages, five that received IRS with PM in October–November 2016 and again in October–November 2017 and five that received no IRS, indoor light trap collections and paired indoor-outdoor human landing collections catches (HLCs) were conducted monthly from September 2016 through October 2018. A universal coverage campaign in June 2017, just prior to the second spray round, distributed 131,540 standard alpha-cypermethrin LLINs across all study villages and increased overall net usage rates in children under 5 years old to over 90%. Results The primary malaria vector during the trial was Anopheles funestus sensu lato (s.l.), and standard World Health Organization (WHO) tube tests with this population indicated variable but increasing resistance to pyrethroids (including alpha-cypermethrin, from > 85% mortality in 2017 to 7% mortality in 2018) and uniform susceptibility to PM (100% mortality in both years). Over the entire duration of the study, IRS reduced An. funestus s.l. densities by 48% (CI95 33–59%; p < 0.001) in indoor light traps and by 74% (CI95 38–90%; p = 0.010) during indoor and outdoor HLC, though in each study year reductions in vector density were consistently greatest in those months immediately following the IRS campaigns and waned over time. Overall there was no strong preference for An. funestus to feed indoors or outdoors, and these biting behaviours did not differ significantly across study arms: observed indoor-outdoor biting ratios were 1.10 (CI95 1.00–1.21) in no-IRS villages and 0.88 (CI95 0.67–1.15) in IRS villages. The impact of IRS was consistent in reducing HLC exposures both indoors (75% reduction: CI95 47–88%; p = 0. < 0.001) and outdoors (68% reduction: CI95 22–87%; p = 0.012). While substantially fewer Anopheles gambiae s.l. were collected during the study, trends show a similar impact of IRS on this key vector group as well, with a 33% (CI95 7–53%; p = 0.019) reduction in mosquitoes collected in light traps and a non-statistically significant 39% reduction (p = 0.249) in HLC landing rates. Conclusion IRS with PM used in addition to pyrethroid-only LLINs substantially reduced human exposures to malaria vectors during both years of the cluster-randomized controlled trial in Mopeia—a high-burden district where the primary vector, An. funestus s.l., was equally likely to feed indoors or outdoors and demonstrated increasing resistance to pyrethroids. Findings suggest that IRS with PM can provide effective vector control, including in some settings where pyrethroid-only ITNs are widely used. Trial registrationclinicaltrials.gov, NCT02910934. Registered 22 September 2016, https://www.clinicaltrials.gov/ct2/show/NCT02910934.

scholarly journals Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Charles Kakilla ◽  
Alphaxard Manjurano ◽  
Karen Nelwin ◽  
Jackline Martin ◽  
Fabian Mashauri ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Vector ◽  
Lake Victoria ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Vector Species ◽  
Sporozoite Rate ◽  
Pirimiphos Methyl

Abstract Background Vector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk. Methods WHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate. Results Annual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10–12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4–2.9) in unsprayed sites compared to 0.8% (95% CI 0.5–1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites. Conclusion This study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

scholarly journals Efficacy of broflanilide (VECTRON™ T500), a new meta-diamide insecticide, for indoor residual spraying against pyrethroid-resistant malaria vectors

2020 ◽  
Author(s):  
Corine Ngufor ◽  
Renaud Govoetchan ◽  
Augustin Fongnikin ◽  
Estelle Vigninou ◽  
Thomas Syme ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Vector ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Cross Resistance ◽  
Malaria Vector Control ◽  
Application Rates ◽  
Wettable Powder ◽  
Cone Bioassay ◽  
Pirimiphos Methyl

AbstractThe rotational use of insecticides with different modes of action for indoor residual spraying (IRS) is recommended for improving malaria vector control and managing insecticide resistance. A more diversified portfolio of IRS insecticides is required; insecticides with new chemistries which can provide improved and prolonged control of insecticide-resistant vector populations are urgently needed. Broflanilide is a newly discovered insecticide being considered for malaria vector control. We investigated the efficacy of a wettable powder (WP) formulation of broflanilide (VECTRON™ T500) for IRS on mud and cement wall substrates in WHO laboratory and experimental hut studies against pyrethroid-resistant malaria vectors in Benin, in comparison with pirimiphos-methyl CS (Actellic® 300CS). There was no evidence of cross-resistance to pyrethroids and broflanilide in CDC bottle bioassays. In laboratory cone bioassays, mortality of susceptible and pyrethroid-resistant A. gambiae s.l. with broflanilide WP treated substrates was >80% for 6-14 months. At application rates of 100mg/m2 and 150 mg/m2, mortality of wild pyrethroid-resistant A. gambiae s.l. entering treated experimental huts in Covè, Benin was 57%-66% with broflanilide WP and did not differ significantly from pirimiphos-methyl CS (57-66% vs. 56%, P>0.05). Mosquito mortality did not differ between the two application rates and local wall substrate-types tested (P>0.05). Throughout the 6-month hut trial, monthly wall cone bioassay mortality on broflanilide WP treated hut walls remained >80% for both susceptible and resistant strains of A. gambiae s.l.. Broflanilide shows potential to significantly improve the control of malaria transmitted by pyrethroid-resistant mosquito vectors and would thus be a crucial addition to the current portfolio of IRS insecticides.One Sentence SummaryVECTRON™ T500, a new wettable powder formulation of broflanilide developed for indoor residual spraying, showed high and prolonged activity against wild pyrethroid-resistant malaria vectors, on local wall substrates, in laboratory bioassays and experimental household settings in Benin.

scholarly journals Monitoring of Insecticide Resistance in Anopheles culicifacies in Twelve Districts of Madhya Pradesh, Central India (2017–2019)

2022 ◽  
Vol 2022 ◽  
pp. 1-8
Author(s):  
Ashok K. Mishra ◽  
Praveen K Bharti ◽  
Gyan Chand ◽  
Aparup Das ◽  
Himanshu Jayswar ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Indoor Residual Spraying ◽  
Central India ◽  
Control Programme ◽  
Madhya Pradesh ◽  
Control Measures ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
The Impact

Background. Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are malaria vector control measures used in India, but the development of insecticide resistance poses major impediments for effective vector control strategies. As per the guidelines of the National Vector Borne Disease Control Programme (NVBDCP), the study was conducted in 12 districts of Madhya Pradesh to generate data on insecticide resistance in malaria vectors. Methods. The susceptibility tests were conducted on adult An. culicifacies as per the WHO standard technique with wild-caught mosquitoes. The blood-fed female mosquitoes were exposed in 3 to 4 replicates on each occasion to the impregnated papers with specified discriminating dosages of the insecticides (DDT: 4%, malathion: 5%, deltamethrin: 0.05%, and alphacypermethrin: 0.05%), for one hour, and mortality was recorded after 24-hour holding. Results. An. culicifacies was found resistant to DDT 4% in all the 12 districts and malathion in 11 districts. The resistance to alphacypermethrin was also observed in two districts, and possible resistance was found to alphacypermethrin in seven districts and to deltamethrin in eight districts, while the vector was found susceptible to both deltamethrin and alphacypermethrin in only 3 districts. Conclusion. An. culicifacies is resistant to DDT and malathion and has emerging resistance to pyrethroids, alphacypermethrin, and deltamethrin. Therefore, regular monitoring of insecticide susceptibility in malaria vectors is needed for implementing effective vector management strategies. However, studies to verify the impact of IRS with good coverage on the transmission of disease are required before deciding on the change of insecticide in conjunction with epidemiological data.

scholarly journals Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

2020 ◽  
Author(s):  
Charles Elias Kakilla ◽  
Alphaxard Manjurano ◽  
Karen Nelwin ◽  
Jackline Martin ◽  
Fabian Mashauri ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Vector ◽  
Lake Victoria ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Vector Species ◽  
Sporozoite Rate ◽  
Pirimiphos Methyl

Abstract BackgroundVector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk.MethodsWHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture potentially resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate. ResultsAnnual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n=4,403 IRS sites, 58%, n=2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto (s.l) in unsprayed sites (20.4%, n=858) than in sprayed sites (7.9%, n=595) and fewer Anopheles parensis (2%, n=85 unsprayed, 7.8%, n=591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10-12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI: 1.4-2.9) in unsprayed sites compared to 0.8% (95% CI: 0.5-1.3) in sprayed sites (p=0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites. ConclusionThis study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

scholarly journals Is outdoor-resting behaviour in malaria vectors consistent? Short report from northern Ghana.

2021 ◽  
Author(s):  
Majidah Hamid-Adiamoh ◽  
Davis Nwakanma ◽  
Isaac Sr ◽  
Alfred Amambua-Ngwa ◽  
Yaw A. Afrane
Keyword(s):  
Fluorescent Dyes ◽  
Indoor Residual Spraying ◽  
Blood Feeding ◽  
Northern Ghana ◽  
Malaria Vectors ◽  
Short Report ◽  
Insecticide Treated Nets ◽  
Resting Behaviour ◽  
Vector Population ◽  
Outdoor Resting

Abstract Background Recent reports of a change in the resting behaviour of malaria vectors, from predominantly indoor resting to outdoor resting following blood feeding, have been attributed to selection pressure from use of vector control tools such as indoor residual spraying and long-lasting insecticide-treated nets. Recent studies have observed vectors resting predominantly outdoors in settings where anti-vector tools are extensively deployed. This present study examined if the outdoor resting behaviour in the vector population, is random or indicative of a consistent preference of one resting site over the other. Methods Mark-release-recapture (MRR) experiments were conducted with outdoor-resting Anopheles gambiae and An. funestus mosquitoes collected from pit shelters, animal houses and granaries in two villages in Northern Ghana during rainy and dry seasons. Mosquitoes were marked with fluorescent dyes and released indoors. The experiments were controlled with indoor-resting mosquitoes, which were marked and released outdoors. Species of all recaptured mosquitoes were identified and assessed for consistency in their resting behaviour. Results A total of 4,460 outdoor-resting mosquitoes comprising An. gambiae sensu lato (s.l.) (2,630, 59%) and An. funestus complex (1,830, 41%) were marked and released. Overall, 31 (0.7%) mosquitoes were recaptured mostly from outdoor location comprising 25 (81%) An. gambiae s.l. and 6 (19%) An. funestus complex. Only 3 (10%) of the recaptured mosquitoes were found resting indoors where they were released. The majority of the outdoor-recaptured mosquitoes were An. arabiensis (11, 39%), followed by An. coluzzii (7, 25%); whereas all indoor-recaptured mosquitoes were An. coluzzii. For the control experiment, 324 indoor-resting mosquitoes constituting 313 (97%) An. gambiae s.l. and 11 (3%) An. funestus complex were marked and released. However, none of these was recaptured neither indoors nor outdoors. More mosquitoes were significantly captured and recaptured during rainy season ( Z = 6.579, P < 0.0001). Conclusions The results obtained suggested the tendency for the mosquitoes to retain their outdoor-resting behaviour. Further investigations are required to ascertain if emerging preference for outdoor resting behaviour in malaria vector populations is consistent or a random occurrence.

scholarly journals An evaluation of repellency and feeding inhibition of ethno-medicinal plants against major malaria vectors in southern Ethiopia

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Tekle Olbamo ◽  
Endashaw Esayas ◽  
Tizazu Gebre ◽  
Fekadu Massebo
Keyword(s):  
Medicinal Plants ◽  
Mosquito Control ◽  
Feeding Activity ◽  
Residual Effect ◽  
Malaria Vectors ◽  
Southern Ethiopia ◽  
Control Methods ◽  
Plant Materials ◽  
The Mean ◽  
The Impact

Abstract Background Plant-based mosquito control methods may use as a supplementary malaria vector control strategy. This study aimed to evaluate the effect of smoking ethno-medicinal plants on indoor density and feeding activity of malaria vectors at early hours of the night and its residual effect after midnight in southern Ethiopia. Methods Both field and tent trials were conducted to evaluate the impact of smoking Juniperus procera leaves, Eucalyptus globulus seeds and Olea europaea leaves in Kolla Shara Village from July 2016 to February 2017. For the field trial, five grass-thatched traditional huts (three for ethno-medicinal plants and two as control [only charcoal smoking and non-charcoal smoking]) were used. Indoor host-seeking mosquitoes were collected by CDC light traps. A Latin square design was employed to minimize the bias due to the variation in house location and different sampling nights. For the tent experiment, 25 3–5-day-old starved wild female Anopheles mosquitoes reared from the larvae were released into the tents where a calf was tethered at the mid-point of each tent. Results A total of 614 Anopheles mosquitoes belonging to 5 species were collected from 5 huts, of which 93.4% was An. arabiensis; O. europaea, E. globulus and J. procera reduced the indoor density of An. arabiensis, with the mean percentage drop of 80%, 73% and 70%, respectively. In the tent trial, smoking of these plants had significant knockdown effects and inhibited feeding on the calves (F = 383.5, DF = 3, P < 0.01). The mean knockdown effect due to O. europaea was relatively high (17.7 ± 0.54; 95% CI 16.8–18.6), while it was only 0.9 ± 0.1 (95% CI 0.29–1.52) in the control tents. All the test plants used in the tent trial caused significantly inhibited feeding activity of An. arabiensis on the host (F = 383.5, DF = 3, P < 0.01). About 94.5%, 89.5% and 86% of mosquitoes were unfed because of the smoking effect of O. europaea, E. globulus and J. procera, respectively, whereas only 19.5% were unfed in the control tent. Conclusions Smoking ethno-medicinal plant materials reduced indoor density of malaria vectors and inhibited feeding on calves inside the tents. Thus, plant-based mosquito control methods may play a vital role in reducing mosquito bites in the early hours of the night and thereby reduce residual malaria transmission.

scholarly journals Is Outdoor-Resting Behaviour in Malaria Vectors Consistent? Short Report From Northern Ghana.

2021 ◽  
Author(s):  
Majidah Hamid-Adiamoh ◽  
Davis Nwakanma ◽  
Isaac Sr ◽  
Alfred Amambua-Ngwa ◽  
Yaw A Afrane
Keyword(s):  
Fluorescent Dyes ◽  
Indoor Residual Spraying ◽  
Blood Feeding ◽  
Northern Ghana ◽  
Malaria Vectors ◽  
Short Report ◽  
Insecticide Treated Nets ◽  
Resting Behaviour ◽  
Vector Population ◽  
Outdoor Resting

Abstract BackgroundRecent reports of a change in the resting behaviour of malaria vectors, from predominantly indoor resting to outdoor resting following blood feeding, have been attributed to selection pressure from use of vector control tools such as indoor residual spraying and long-lasting insecticide-treated nets. Recent studies have observed vectors resting predominantly outdoors in settings where anti-vector tools are extensively deployed. This present study examined if the outdoor resting behaviour in the vector population, is random or indicative of a consistent preference of one resting site over the other. MethodsMark-release-recapture (MRR) experiments were conducted with outdoor-resting Anopheles gambiae and An. funestus mosquitoes collected from pit shelters, animal houses and granaries in two villages in Northern Ghana. Mosquitoes were marked with fluorescent dyes and released indoors. The experiments were controlled with indoor-resting mosquitoes, which were marked and released outdoors. Species of all recaptured mosquitoes were identified and assessed for consistency in their resting behaviour. ResultsA total of 4,460 outdoor-resting mosquitoes comprising An. gambiae sensu lato (s.l.) (59%) and An. funestus complex (41%) were marked and released. Overall, 31 (0.7%) mosquitoes (25 An. gambiae s.l. and 6 An. funestus complex) were recaptured mostly from outdoor location. Only 3 of the recaptured mosquitoes were found resting indoors where they were released. The majority of the outdoor-recaptured mosquitoes were An. arabiensis (11, 39%), followed by An. coluzzii (7, 25%); whereas the indoor-recaptured mosquitoes were mainly (3) An. coluzzii. For the control experiment, 324 indoor-resting mosquitoes constituting 313 An. gambiae s.l. and 11 An. funestus complex were marked and released. However, none of these was recaptured neither indoors nor outdoors.ConclusionsThe mosquitoes demonstrated the tendency to retain their outdoor-resting behaviour. Further investigations are required to ascertain if emerging preference for outdoor resting behaviour in malaria vector populations is consistent or a random occurrence.

scholarly journals Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

2020 ◽  
Author(s):  
Charles Elias Kakilla ◽  
Alphaxard Manjurano ◽  
Karen Nelwin ◽  
Jackline Martin ◽  
Fabian Mashauri ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Vector ◽  
Lake Victoria ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Vector Species ◽  
Sporozoite Rate ◽  
Pirimiphos Methyl ◽  
The Impact

Abstract Background: Vector control through long lasting insecticidal nets and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza and Mara. Entomological surveillance was conducted in ten sprayed and four unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk. Methods: WHO Cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (un-baited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture potentially resting malaria vector. A sub-sample of Anopheles were tested by PCR to determine species identity and ELISA for sporozoite rate. Results: Annual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly An. arabiensis (58.1%, n=4,403 IRS sites, 58%, n=2,441 unsprayed sites). There was a greater proportion of An. funestus s.s. in unsprayed sites (20.4%, n=858) than sprayed sites (7.9%, n=595) and fewer An. parensis (2%, n=85 unsprayed, 7.8%, n=591 sprayed). Biting peaks of An. gambiae s.l. followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e. 10-12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI: 1.4-2.9) in unsprayed sites compared to 0.8% (95% CI: 0.5-1.3) in sprayed sites (p=0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites. Conclusion: This study contributes to the understanding of malaria vector species composition, behavior and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

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