Bacterial larvicides for vector control: mode of action of toxins and implications for resistance

Ferreira, Lígia Maria; Silva-Filha, Maria Helena Neves Lobo

doi:10.1080/09583157.2013.822472

Cited by 24 publications

(20 citation statements)

References 188 publications

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“…The ICPs produced by Bti comprise both CYT and CRY proteins. The CYT proteins act synergistically with the CRY proteins (Ferreira and Silva-Filha 2013) and larvae possibly consumed various ratios of these proteins thereby causing differences in the time it takes to achieve mortality.…”

Section: Discussionmentioning

confidence: 99%

Mortality Patterns ofSimulium vittatumLarvae (Diptera: simuliidae) Following Exposure to Insecticidal Proteins Produced byBacillus thuringiensisVar.israelensis

Iburg

Gray²,

Noblet³

2015

Journal of the American Mosquito Control Association

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Products containing insecticidal crystalline proteins (ICPs) produced by Bacillus thuringiensis var. israelensis (Bti ICPs) are used to suppress vector and nuisance populations of black flies. The efficacy of an application of these products is often determined by a posttreatment evaluation of larval mortality. Larvae are typically removed from the substrate at some point in time after application of the product and mortality is determined. The time necessary for the effects of Bti ICPs to cause morality in exposed larvae can vary, and there is little consensus on how long operators should wait before evaluating larval mortality. This study was conducted to provide more information to larvicide applicators when performing posttreatment evaluations. Simulium vittatum larvae were exposed to Bti ICPs under controlled conditions and the mortality was monitored over time. Larvae exposed to operational concentrations of ICPs exhibited maximum mortality, approximately 87%, after 4 h. Exposure of larvae to 1/3 of that concentration resulted in similar mortality; however, the maximum mortality was not reached until 8 h postexposure. Additional experiments revealed that maximum mortality and time to maximum mortality can also be affected by components in the larval medium. Larval mortality was compared between larvae exposed to Bti ICPs in moderately hard water, medium containing 50 parts per million (ppm) of kaolinite, and medium containing 50 ppm of cellulose. The clay material had no significant effect on larval mortality or time to achieve maximum mortality. When cellulose was present in the medium, the time to maximum mortality was increased 50% and overall mortality was reduced by more than 40%.

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Section: Discussionmentioning

confidence: 99%

Mortality Patterns ofSimulium vittatumLarvae (Diptera: simuliidae) Following Exposure to Insecticidal Proteins Produced byBacillus thuringiensisVar.israelensis

Iburg

Gray²,

Noblet³

2015

Journal of the American Mosquito Control Association

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“…Interestingly, evaluation of eld populations of Cx. pipiens without history of Bti exposure has shown variations of resistance ratios ranging from less than 3-to 10-fold [23]. Therefore, this inherent variability in Cx.…”

Section: Introductionmentioning

confidence: 99%

Resistance Development to Diflubenzuron and Bacillus Thuringiensis Subsp. Israelensis of Culex Pipiens f. Pipiens and Culex Pipiens f. Molestus (Diptera: Culicidae) and its Effects on Their Winter Survival

Ioannou¹,

Hadjichristodoulou²,

Kyritsi³

et al. 2020

Preprint

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Background: The Culex pipiens mosquito consists of two forms named pipiens and molestus that exhibit substantial differences in their biology including overwintering behavior. Diflubenzuron (DFB) and Bacillus thuringiensis subsp. israelensis (Bti) are among the most widely used larvicides for controlling Cx. pipiens populations. The high dependency on these two larvicides, pose major concerns for resistance development. The evolution and stability of resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions such as the winter period. The aim of the present study was to explore the resistance development of pipiens and molestus forms to both larvicides and its potential fitness costs on their winter survival.Methods: Colonies of both forms of Cx. pipiens were established from the same area. Following the World Health Organization protocols (WHO), the efficacy of both larvicides was determined for each mosquito population. Then, larvae from each form were selected for three successive generations by applying fixed doses corresponding to IE80 (IE: Inhibition of adult Emergence) and LC80 (LC: Lethal Concentration) for DFB and Bti respectively. At the end of this process, the resistance levels and the winter survival of the selected populations relative to controls (colonies that received no selection) were determined.Results: Contrary to Bti, selection with DFB induced different levels of resistance between the two forms of Cx. pipiens. The selected populations of Cx. pipiens f. molestus to both larvicides exhibited a high fitness cost in terms of reduced winter larval survival rates relative to control. Moreover, the obtained adults of the Bti selected population experienced significantly shorter lifespan compared to control and DFB selected population. On the other hand, selection with both DFB and Bti had no apparent effects on Cx. pipiens f. pipiens female winter survival rates relative to control. Furthermore, the reproductive parameters and the longevity of the overwintered females were similar between the selected populations and the control. Conclusions: Our findings are expected to contribute on the better understanding of the resistance development and evolution of the two forms of Cx. pipiens to DFB and Bti allowing the adoption of appropriate resistance management strategies.

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“…The larval stages develop in fast-moving rivers and streams and feed primarily by using cephalic fans to filter particles from the flowing water (Chance, 1970). A thorough understanding of larval feeding behavior is crucial for successful control strategies considering that biologically based larvicides must be ingested to become active (Ferreira & Silva-Filha, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The application of products containing insecticidal crystalline proteins (ICPs) produced by Bacillus thuringiensis Berliner ssp. israelensis (Bti) has been a successful strategy for suppressing nuisance populations since 1980 (Ferreira & Silva-Filha, 2013). Formulations that contain the ICPs typically contain larger particles to which the proteins are bound.…”

Section: Introductionmentioning

confidence: 99%

“…The larger particles are captured by the cephalic fans of the larvae more efficiently resulting in higher larval mortality (de Barjac & Sutherland, 1990). The ICPs are solubilized in the gut of the larvae and acted on by proteases thus converting the pro-toxin into a toxin (Ferreira & Silva-Filha, 2013). Black fly larvae are only exposed to the ICPs for a brief period of time following application due to the nature of the larval habitat.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Feeding behavior of Simulium vittatum larvae in response to various suspended materials: implications for control using biological larvicides

Iburg

Gray

Noblet

2016

Entomologia Exp Applicata

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Biologically based larvicides used to suppress nuisance populations of black flies (Diptera: Simuliidae) require that the larvae ingest the larvicide for mortality to occur. Materials present in the habitat that alter larval feeding behavior may reduce the effectiveness of the larvicide. This study was conducted to determine the effects that commonly occurring materials in larval habitats have on Simulium vittatum Zetterstedt feeding behavior. Larvae were exposed to 50 p.p.m. of kaolinite clay and 4 p.p.m. of purified diatom frustules. Larvae were also exposed to 10 000 cells or colonies per ml of viable green algae, Chlorella vulgaris Pratt and Scenedesmus quadricauda (Turp) Bréb, and the diatom Cyclotella meneghiniana Kützing to determine the effects that these materials have on larval feeding behavior. Individual larvae were recorded using a digital camcorder to determine the average number of times the larvae extended and retracted their cephalic fans per min (flick rate) in each medium. Following exposure to the selected material, neon red particles (NRP) (DayGlo) were added to the larval medium for 20 min. A spectrophotometric analysis was conducted to determine the average quantity of NRP consumed by larvae per min in each medium. The flick rate and quantity of NRP consumed by larvae was not significantly affected by clay material or viable Chlorella cells. When Scenedesmus colonies or Cyclotella cells were present in the larval medium, larval flick rate and NRP ingestion was significantly reduced. The presence of diatom frustules in the medium resulted in the most severe reduction in larval flick rate and NRP ingestion. The results suggest that larval flick rate can change depending on environmental conditions, and that suppression programs using biologically based larvicides may benefit from investigating the potential correlation between algal counts and treatment efficacy.

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Bacterial larvicides for vector control: mode of action of toxins and implications for resistance

Cited by 24 publications

References 188 publications

Mortality Patterns ofSimulium vittatumLarvae (Diptera: simuliidae) Following Exposure to Insecticidal Proteins Produced byBacillus thuringiensisVar.israelensis

Mortality Patterns ofSimulium vittatumLarvae (Diptera: simuliidae) Following Exposure to Insecticidal Proteins Produced byBacillus thuringiensisVar.israelensis

Resistance Development to Diflubenzuron and Bacillus Thuringiensis Subsp. Israelensis of Culex Pipiens f. Pipiens and Culex Pipiens f. Molestus (Diptera: Culicidae) and its Effects on Their Winter Survival

Feeding behavior of Simulium vittatum larvae in response to various suspended materials: implications for control using biological larvicides

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