Field evaluation of Veeralin, an alpha-cypermethrin + PBO long-lasting insecticidal net, against natural populations of Anopheles funestus in experimental huts in Muheza, Tanzania

Background: Metabolic resistance is a serious challenge to current insecticide-based interventions. The extent to which it affects natural populations of mosquitoes including their reproduction ability remains uncharacterised. Here, we investigated the potential impact of the glutathione S-transferase L119F-GSTe2 resistance on the mating competitiveness of male Anopheles funestus, in Cameroon. Methods: Swarms and indoor resting collections took place in March, 2018 in Tibati, Cameroon. WHO tube and cone assays were performed on F1 mosquitoes from indoor collected females to assess the susceptibility profile of malaria vectors. Mosquitoes mated and unmated males collected in the swarms were genotyped for the L119F metabolic marker to assess its association with mating male competitiveness. Results: Susceptibility and synergist assays, showed that this population was multiple resistant to pyrethroids, DDT and carbamates, likely driven by metabolic resistance mechanisms. Cone assays revealed a reduced efficacy of standard pyrethroid-nets (Olyset and PermaNet 2.0) with low mortality (<25%) whereas synergist PBO-Nets (Olyset Plus and PermaNet 3.0) retained greater efficacy with higher mortality (>80%). The L119F-GSTe2 mutation, conferring pyrethroid/DDT resistance, was detected in this An. funestus population at a frequency of 28.8%. In addition, a total of 15 mating swarms were identified and 21 An. funestus couples were isolated from those swarms. A comparative genotyping of the L119F-GSTe2 mutation between mated and unmated males revealed that heterozygote males 119L/F-RS were less able to mate than homozygote susceptible (OR=7.2, P<0.0001). Surprisingly, heterozygote mosquitoes were also less able to mate than homozygote resistant (OR=4.2, P=0.010) suggesting the presence of a heterozygote disadvantage effect. Overall, mosquitoes bearing the L119-S susceptible allele were significantly more able to mate than those with 119F-R resistant allele (OR=2.1, P=0.03). Conclusion: This study provides preliminary evidences that metabolic resistance potentially exerts a fitness cost on mating competiveness in resistant mosquitoes.

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Efficacy of two PBO long lasting insecticidal nets against natural populations of Anopheles gambiae s.l. in experimental huts, Kolokopé, Togo

PLoS ONE ◽

10.1371/journal.pone.0192492 ◽

2018 ◽

Vol 13 (7) ◽

pp. e0192492 ◽

Cited By ~ 8

Author(s):

Guillaume K. Ketoh ◽

Koffi M. Ahadji-Dabla ◽

Joseph Chabi ◽

Adjovi D. Amoudji ◽

Georges Y. Apetogbo ◽

...

Keyword(s):

Anopheles Gambiae ◽

Natural Populations ◽

Experimental Huts ◽

Anopheles Gambiae S.L ◽

Long Lasting Insecticidal Nets

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Bio-efficacy and wash resistance of MAGNet long-lasting insecticidal net against wild populations of Anopheles funestus in experimental huts in Muheza, Tanzania

Malaria Journal ◽

10.1186/s12936-019-2973-x ◽

2019 ◽

Vol 18 (1) ◽

Author(s):

Eliningaya J. Kweka ◽

Patrick K. Tungu ◽

Aneth M. Mahande ◽

Humphrey D. Mazigo ◽

Subira Sayumwe ◽

...

Keyword(s):

Anopheles Funestus ◽

Blood Feeding ◽

Personal Protection ◽

Feeding Rates ◽

Feeding Inhibition ◽

Experimental Huts ◽

Host Seeking ◽

Mosquito Mortality ◽

Resistant Population ◽

Long Lasting Insecticidal Nets

Abstract Background The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35–7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus. Methods MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05). Results The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN. Conclusion Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.

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Small-scale field evaluation of push-pull system against early- and outdoor-biting malaria mosquitoes in an area of high pyrethroid resistance in Tanzania

Wellcome Open Research ◽

10.12688/wellcomeopenres.13006.1 ◽

2017 ◽

Vol 2 ◽

pp. 112 ◽

Cited By ~ 4

Author(s):

Arnold S. Mmbando ◽

Halfan S. Ngowo ◽

Masoud Kilalangongono ◽

Said Abbas ◽

Nancy S. Matowo ◽

...

Keyword(s):

Pyrethroid Resistance ◽

Field Evaluation ◽

Blood Feeding ◽

Small Scale ◽

Insecticide Treated Nets ◽

High Coverage ◽

Pull System ◽

Experimental Huts ◽

Outdoor Biting ◽

Significant Difference

Background: Despite high coverage of indoor interventions like insecticide-treated nets, mosquito-borne infections persist, partly because of outdoor-biting, early-biting and insecticide-resistant vectors. Push-pull systems, where mosquitoes are repelled from humans and attracted to nearby lethal targets, may constitute effective complementary interventions. Methods: A partially randomized cross-over design was used to test efficacy of push-pull in four experimental huts and four local houses, in an area with high pyrethroid resistance in Tanzania. The push-pull system consisted of 1.1% or 2.2% w/v transfluthrin repellent dispensers and an outdoor lure-and-kill device (odour-baited mosquito landing box). Matching controls were set up without push-pull. Adult male volunteers collected mosquitoes attempting to bite them outdoors, but collections were also done indoors using exit traps in experimental huts and by volunteers in the local houses. The collections were done hourly (1830hrs-0730hrs) and mosquito catches compared between push-pull and controls. An. gambiae s.l. and An. funestus s.l. were assessed by PCR to identify sibling species, and ELISA to detect Plasmodium falciparum and blood meal sources. Results: Push-pull in experimental huts reduced outdoor-biting for An. arabiensis and Mansonia species by 30% and 41.5% respectively. However, the reductions were marginal and insignificant for An. funestus (12.2%; p>0.05) and Culex (5%; p>0.05). Highest protection against all species occurred before 2200hrs. There was no significant difference in number of mosquitoes inside exit traps in huts with or without push-pull. In local households, push-pull significantly reduced indoor and outdoor-biting of An. arabiensis by 48% and 25% respectively, but had no effect on other species. Conclusion: This push-pull system offered modest protection against outdoor-biting An. arabiensis, without increasing indoor mosquito densities. Additional experimentation is required to assess how transfluthrin-based products affect mosquito blood-feeding and mortality in push-pull contexts. This approach, if optimised, could potentially complement existing malaria interventions even in areas with high pyrethroid resistance.

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Chromosomal and environmental determinants of morphometric variation in natural populations of the malaria vector Anopheles funestus in Cameroon

Infection Genetics and Evolution ◽

10.1016/j.meegid.2011.03.003 ◽

2011 ◽

Vol 11 (5) ◽

pp. 940-947 ◽

Cited By ~ 37

Author(s):

Diego Ayala ◽

Harling Caro-Riaño ◽

Jean-Pierre Dujardin ◽

Nil Rahola ◽

Frederic Simard ◽

...

Keyword(s):

Malaria Vector ◽

Natural Populations ◽

Anopheles Funestus ◽

Environmental Determinants ◽

Morphometric Variation

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Experimental huts trial of the efficacy of pyrethroids/piperonyl butoxide (PBO) net treatments for controlling multi-resistant populations of Anopheles funestus s.s. in Kpomè, Southern Benin

Wellcome Open Research ◽

10.12688/wellcomeopenres.14589.1 ◽

2018 ◽

Vol 3 ◽

pp. 71 ◽

Cited By ~ 2

Author(s):

Romaric Akoton ◽

Genevieve M. Tchigossou ◽

Innocent Djègbè ◽

Akadiri Yessoufou ◽

Michael Seun Atoyebi ◽

...

Keyword(s):

High Performance ◽

Anopheles Funestus ◽

Piperonyl Butoxide ◽

World Health ◽

Experimental Huts ◽

New Generation ◽

Type 3 ◽

Southern Benin

Background: Insecticides resistance in Anopheles mosquitoes limits Long-Lasting Insecticidal Nets (LLIN) used for malaria control in Africa, especially Benin. This study aimed to evaluate the bio-efficacy of current LLINs in an area where An. funestus s.l. and An. gambiae have developed multi-resistance to insecticides, and to assess in experimental huts the performance of a mixed combination of pyrethroids and piperonyl butoxide (PBO) treated nets on these resistant mosquitoes. Methods: The study was conducted at Kpomè, Southern Benin. The bio-efficacy of LLINs against An. funestus and An. gambiae was assessed using the World Health Organization (WHO) cone and tunnel tests. A released/recapture experiment following WHO procedures was conducted to compare the efficacy of conventional LLINs treated with pyrethroids only and LLINs with combinations of pyrethroids and PBO. Prior to huts trials, we confirmed the level of insecticide and PBO residues in tested nets using high performance liquid chromatography (HPLC). Results: Conventional LLINs (Type 2 and Type 4) have the lowest effect against local multi-resistant An. funestus s.s. and An. coluzzii populations from Kpomè. Conversely, when LLINs containing mixtures of pyrethroids and PBO (Type 1 and Type 3) were introduced in trial huts, we recorded a greater effect against the two mosquito populations (P < 0.0001). Tunnel test with An. funestus s.s. revealed mortalities of over 80% with this new generation of LLINs (Type 1 and Type 3),while conventional LLINs produced 65.53 ± 8.33% mortalities for Type 2 and 71.25 ±7.92% mortalities for Type 4. Similarly, mortalities ranging from 77 to 87% were recorded with the local populations of An. coluzzii. Conclusion: This study suggests the reduced efficacy of conventional LLINs (Pyrethroids alone) currently distributed in Benin communities where Anopheles populations have developed multi-insecticide resistance. The new generation nets (pyrethroids+PBO) proved to be more effective on multi-resistant populations of mosquitoes.

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Investigation of the influence of a glutathione S-transferase metabolic resistance to pyrethroids/DDT on mating competitiveness in males Anopheles funestus, African malaria vector

Wellcome Open Research ◽

10.12688/wellcomeopenres.15013.1 ◽

2019 ◽

Vol 4 ◽

pp. 13 ◽

Cited By ~ 3

Author(s):

Magellan Tchouakui ◽

Billy Tene Fossog ◽

Brigitte Vanessa Ngannang ◽

Doumani Djonabaye ◽

Williams Tchapga ◽

...

Keyword(s):

Natural Populations ◽

Anopheles Funestus ◽

Resistance Mechanisms ◽

Malaria Vectors ◽

Glutathione S Transferase ◽

Metabolic Resistance ◽

Mating Competitiveness ◽

Metabolic Marker ◽

Susceptible Allele ◽

Permanet 3.0

Background: Metabolic resistance is a serious challenge to current insecticide-based interventions. The extent to which it affects natural populations of mosquitoes including their reproduction ability remains uncharacterised. Here, we investigated the potential impact of the glutathione S-transferase L119F-GSTe2 resistance on the mating competitiveness of male Anopheles funestus, in Cameroon. Methods: Swarms and indoor resting collections took place in March, 2018 in Tibati, Cameroon. WHO tube and cone assays were performed on F1 mosquitoes from indoor collected females to assess the susceptibility profile of malaria vectors. Mosquitoes mated and unmated males collected in the swarms were genotyped for the L119F metabolic marker to assess its association with mating male competitiveness. Results: Susceptibility and synergist assays, showed that this population was multiple resistant to pyrethroids, DDT and carbamates, likely driven by metabolic resistance mechanisms. Cone assays revealed a reduced efficacy of standard pyrethroid-nets (Olyset and PermaNet 2.0) with low mortality (<25%) whereas synergist PBO-Nets (Olyset Plus and PermaNet 3.0) retained greater efficacy with higher mortality (>80%). The L119F-GSTe2 mutation, conferring pyrethroid/DDT resistance, was detected in this An.funestus population at a frequency of 28.8%. In addition, a total of 15 mating swarms were identified and 21 An. funestus couples were isolated from those swarms. A comparative genotyping of the L119F-GSTe2 mutation between mated and unmated males revealed that heterozygote males 119L/F-RS were less able to mate than homozygote susceptible (OR=7.2, P<0.0001). Surprisingly, heterozygote mosquitoes were also less able to mate than homozygote resistant (OR=4.2, P=0.010) suggesting the presence of a heterozygote disadvantage effect. Overall, mosquitoes bearing the L119-S susceptible allele were significantly more able to mate than those with 119F-R resistant allele (OR=2.1, P=0.03). Conclusion: This study provides preliminary evidences that metabolic resistance potentially exerts a fitness cost on mating competiveness in resistant mosquitoes.

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Wild populations of malaria vectors can mate both inside and outside human dwellings

Parasites & Vectors ◽

10.1186/s13071-021-04989-8 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Ismail H. Nambunga ◽

Betwel J. Msugupakulya ◽

Emmanuel E. Hape ◽

Issa H. Mshani ◽

Najat F. Kahamba ◽

...

Keyword(s):

Anopheles Arabiensis ◽

Anopheles Funestus ◽

Alternative Methods ◽

Malaria Vectors ◽

Field Observations ◽

Ecological Significance ◽

Wild Populations ◽

Time Points ◽

Experimental Huts ◽

The Village

Abstract Background Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings. Method Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps. Results Proportions of inseminated females inside the experimental huts in the village increased from approximately 60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps. Conclusion Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers. Graphical Abstract

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Studies in House Leaving and Outside Resting of Anopheles gambiae Giles and Anopheles funestus Giles in East Africa. II.—The Exodus from Houses and the House Resting Population

Bulletin of Entomological Research ◽

10.1017/s000748530002719x ◽

1954 ◽

Vol 45 (2) ◽

pp. 375-387 ◽

Cited By ~ 29

Author(s):

M. T. Gillies

Keyword(s):

Anopheles Gambiae ◽

Ovarian Development ◽

Anopheles Funestus ◽

Cool Season ◽

Natural Conditions ◽

Experimental Hut ◽

Experimental Huts ◽

Hot Season ◽

Anopheles Gambiae Giles ◽

Made In

Observations on the behaviour of Anopheles gambiae Giles and A. funestus Giles in experimental huts and ordinary African houses were carried out in a low-lying area of Tanganyika. Special attention was paid to the exodus of females at different stages of the gonotrophic cycle and to the composition in terms of ovarian development of the house resting population.About 5 per cent. of the biting population of gambiae and the same number of funestus were shown by the use of window traps to be leaving experimental huts after feeding.Forty three per cent. of half-gravid gambiae left an experimental hut at dusk, 12–24 hours after entering for a blood meal, whereas only 3 per cent. of funestus left under the same conditions.Daytime spray catches of gravid gambiae and funestus made in ordinary African houses during the hot season were about 50 per cent. and 30 per cent. lower, respectively, than the corresponding numbers of recently fed specimens. A. funestus therefore makes rather less use of outside shelters than gambiae during the hot months.In the cool season about 50 per cent. of half-gravid and gravid funestus were absent from house catches.No mortality could be detected amongst funestus females resting under natural conditions for 24 hours in an experimental hut.Re-entry of gravid funestus into unoccupied and open types of inhabited houses occurs at dawn.

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High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103875 ◽

1988 ◽

Vol 46 ◽

pp. 362-363

Author(s):

G. E. Tyson ◽

M. J. Song

Keyword(s):

Electron Microscopy ◽

High Voltage ◽

Brine Shrimp ◽

Natural Populations ◽

Three Dimensional ◽

Dimensional Structure ◽

High Voltage Electron Microscopy ◽

Voltage Electron ◽

High Voltage Electron ◽

Infected Adult

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.

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