Bacillus Thuringiensis Israelensis for the Control of Dengue Vectors Systematic Literature Review

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Bacillus thuringiensis israelensis (Bti) for the control of dengue

vectors: systematic literature review

R. Boyce1, A. Lenhart2, A. Kroeger 2,3, R. Velayudhan4, B. Roberts5 and O. Horstick 6

1 Department of Internal Medicine, Massachusetts General Hospital, Boston, MA, USA2 Liverpool School of Tropical Medicine, Liverpool, UK3 Special Programme for Research and Training in Tropical Diseases, World Health Organization, Geneva, Switzerland 4 Department for the Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland 5 London School of Hygiene, Tropical Medicine, London, UK6 Institute of Public Health & University of Heidelberg, Heidelberg, Germany

Abstract objective To systematically review the literature on the effectiveness of Bacillus thuringiensis

israelensis (Bti) , when used as a single agent in the field, for the control of dengue vectors.

method Systematic literature search of the published and grey literature was carried out using the

following databases: MEDLINE, EMBASE, Global Health, Web of Science, the Cochrane Library,WHOLIS, ELDIS, the New York Academy of Medicine Gray Literature Report, Africa-Wide and

Google. All results were screened for duplicates and assessed for eligibility. Relevant data were

extracted, and a quality assessment was conducted using the CONSORT 2010 checklist.

results Fourteen studies satisfied the eligibility criteria, incorporating a wide range of interventions

and outcome measures. Six studies were classified as effectiveness studies, and the remaining eight

examined the efficacy of Bti in more controlled settings. Twelve (all eight efficacy studies and 4 of 6

effectiveness studies) reported reductions in entomological indices with an average duration of control

of 2 – 4 weeks. The two effectiveness studies that did not report significant entomological reductions

were both cluster-randomised study designs that utilised basic interventions such as environmental

management or general education on environment control practices in their respective control groups.

Only one study described a reduction in entomological indices together with epidemiological data,

reporting one dengue case in the treated area compared to 15 dengue cases in the untreated area

during the observed study period.conclusion While Bti can be effective in reducing the number of immature Aedes in treated

containers in the short term, there is very limited evidence that dengue morbidity can be reduced

through the use of Bti alone. There is currently insufficient evidence to recommend the use of Bti as a

single agent for the long-term control of dengue vectors and prevention of dengue fever. Further

studies examining the role of Bti in combination with other strategies to control dengue vectors are

warranted.

keywords dengue, vector control, Bacillus thuringiensis israelensis, Aedes

Introduction

Dengue is the most rapidly advancing vector-borne dis-

ease in the world (Special Programme for Research andTraining in Tropical Diseases, WHO/TDR 2007). Over-

all, it is estimated that 2.5 billion people, or roughly one-

third of the world’s population, live in dengue-endemic

areas. Annually, an estimated 50 – 100 million cases of

dengue fever and several hundred thousand cases of

severe dengue occur.

In the absence of any vaccine and preventive drugs,

controlling the mosquito vectors of dengue (principally

Aedes aegypti) is the only way to prevent and control

dengue transmission. Chemical and biological agents

remain important components of dengue vector control

programmes. Unfortunately, the widespread use of chemi-cal insecticides has contributed to increasing resistance to

these agents among A. aegypti, especially in the Americas

and the Caribbean (Rodriguez et al. 2005; Harris et al.

2010).

Biological control, ‘based on the introduction of organ-

isms that prey upon, parasitise, compete with or other-

wise reduce populations of the target species’, is

considered a practical alternative to the application of

564 © 2013 Blackwell Publishing Ltd

Tropical Medicine and International Health doi:10.1111/tmi.12087

volume 18 no 5 pp 564 – 577 may 2013



chemical insecticides in controlling mosquito vectors of

disease (Special Programme for Research and Training in

Tropical Diseases, WHO/TDR 2009). In addition to

reducing both toxicity to non-target species and environ-

mental contamination, biological control also offersreduced potential for resistance development. However,

biological control agents can be comparatively expensive

and logistically more challenging to deploy and maintain

compared to traditional chemical agents.

Bacillus thuringiensis var. israelensis (Bti) is a gram-

positive, spore-forming entomopathogenic bacterium first

isolated in 1976 (Goldberg & Margalit 1977). As a bio-

logical control agent, Bti has demonstrated high efficacy

against target organisms, primarily mosquito and black

fly larvae (Mittal 2003; Lacey 2007). Bacillus thuringien-

sis israelensis exerts its lethal effects through producing a

variety of toxic proteins that are ingested by the larvae of

susceptible organisms. These toxins are then activated inthe gut of the larvae where they cause disruption of the

cell membranes and death of the organism. The specific-

ity of this mechanism has been demonstrated in multiple

studies with no adverse effects on non-target inverte-

brates and vertebrates (Lee & Scott 1989; Merritt et al.

1989; Lacey & Mulla 1990; Saik et al. 1990). Because of

the complex mechanism of action involving many pro-

teins, the potential for resistance development is greatly

reduced. Bacillus thuringiensis israelensis is available in a

number of formulations that can be applied by hand or

with conventional spray equipment (Lacey 2007), allow-

ing Bti to be utilised in a variety of breeding habitats.

To date, no systematic review of the scientific literaturehas been undertaken to examine the evidence for the

effectiveness of Bti against dengue vectors. The objective

of this study was to provide a systematic review of the

effectiveness of Bti, when used as a single agent in the

field, for the control of dengue vectors and prevention of

dengue fever.

Methods

This review follows the reporting guidelines set forth in

the PRISMA statement for systematic reviews and meta-

analyses (Liberati et al. 2009).

Eligibility criteria

The eligibility criteria for the reviewed literature included

the following: (i) research with an experimental design

producing primary quantitative data, (ii) research con-

ducted in the field, defined as any community or environ-

ment where dengue vectors naturally occur, (iii) the use

of Bti as a single agent to control dengue vectors, (iv)

clear information on Bti formulation and dosing, (v)

outcome measures reported as immature indices (i.e.

Stegomyia indices, oviposition indices and/or presence/

absence of immature stages of Aedes) and (vi) a mini-

mum follow-up period of at least 20 days. Only litera-ture reported in English was included. Conference

abstracts and proceedings from conferences were

excluded.

Search strategy

The literature search and analysis was developed and car-

ried out through March 2012, by two data extractors.

The search terms derived from three major categories: (i)

dengue disease, which included ‘dengue’ and ‘dengue

hemorrhagic fever’, (ii) the Bti intervention and (iii) the

outcome, which centred on reductions in dengue vector

density as measured by various entomological indices.The search included both free text and subject heading

terms.

The search strategy was applied to the following data-

bases to locate peer-reviewed studies: MEDLINE, EM-

BASE, Global Health, Web of Science, the Cochrane

Library and WHOLIS. The following databases were

searched for grey literature: ELDIS, the New York Acad-

emy of Medicine Gray Literature Report, Africa-Wide

and Google. Because of the limited search options avail-

able in many of the grey literature databases, a broad

search strategy was employed, typically including only

the terms ‘dengue’ and/or ‘Bacillus thuringiensis’.

Study selection, data extraction

All results were screened for duplicates by author, title,

journal and publication date. In the first stage, results

were screened based on the title and abstract only. The

full text of those studies that were not excluded was

then reviewed for final assessment. The reference section

of each of the selected publications was reviewed to

identify additional relevant studies. Relevant informa-

tion, including study design, setting and Bti formulation,

from each of the selected studies was extracted, and

when information was unclear from the reported results,

an attempt was made to contact the correspondingauthor. Studies were first classified as either efficacy

studies, where Bti was placed in targeted containers that

were observed for reductions in immature stages, or

effectiveness studies, where Bti was used to treat con-

tainers or peridomestic areas, and surveyed for reduc-

tions in classical entomological indices. Study designs

were subsequently divided into three categories:

randomised or quasi-randomised controlled trials (RCT),

© 2013 Blackwell Publishing Ltd 565

Tropical Medicine and International Health volume 18 no 5 pp 564 – 577 may 2013

R. Boyce et al. BTI and dengue: a systematic review



cluster-randomised controlled trials (CRCT) and non-

randomised controlled trials (NRCT).

Analysis

Because the majority of the included studies were non-

randomised, it was not possible to utilise an existing, val-

idated instrument for assessing risk of bias. Instead, the

CONSORT 2010 checklist served as a framework to

describe limitations in the conduct and reporting of the

included studies. No studies were excluded for quality

reasons if the eligibility criteria were met, but limitations

and possible biases are reported in the results section.

Different Bti formulations and methods of application,

together with varying statistical analyses and outcome

measures across the studies, precluded any attempt at

meta-analysis.

Results

Study selection

After screening out duplicates, the literature search identi-fied 355 articles for assessment. Fourteen articles met the

eligibility criteria. Of these, nine were identified from the

published literature databases and three from the grey

literature search (Phan-Urai et al. 1995; Haq et al. 2004;

Lam et al. 2010). The most common reasons for exclu-

sion were as follows: interventions did not use Bti (190

studies), the manuscripts were review articles and/or of

non-experimental design (93 articles) or the studies took

place in laboratory or semi-field settings (33 articles). A

review of the references cited in the articles that met the

eligibility criteria yielded one additional study (Dua et al.

1993). One more article (Tan et al. 2012) that was

Academic databases

Medline, EMBASE, Global Health,WHOLIS, Cochrane Library

Gray literature

ELDIS, NY Academy of Medicine GrayLiterature Report, Africa-Wide, Google

Screening for duplicates

Combined results (n = 354)

Screening by title & abstractExcluded (n = 309)

Included (n = 45)

-Bti not studied (n = 190)

-Review or non-experimental design (n = 87)

-Abstract only (n = 18)

-Laboratory or semi-field design (n = 14)

Screening by full text

Met eligibility criteria (n = 12)

Excluded (n = 33)

-Laboratory or semi-field design (n = 19)

-Combination intervention (n = 7)

-Review or non-experimental design (n = 6)

-Non-dengue vector (n = 1)

New study list of references (n = 13)

Newly published study (n = 14)

Included (n = 14)

Figure 1 Flow chart describing paper selection and inclusion/ exclusion process.






published during manuscript preparation was included in

the review. No further studies were included after review-

ing the references of this additional article. Figure 1 sum-

marises the selection process.

The 14 included studies are summarised in Tables 1and 2, in which they are assigned a unique identifier for

reference purposes in the remainder of this manuscript.

General study characteristics

All studies were published between 1993 and 2012. Ten

of the studies were conducted in South-East Asia, with

India being the most common location (1, 2, 3, 5 in

Table 1). Three studies were conducted in South America

(4, 6, 11 in Tables 1 and 2) and one in the Caribbean

(10 in Table 1). In most studies, the setting was selected

because of a high incidence of dengue or elevated pre-

intervention entomological indices. No study incorpo-rated economic analysis or provided cost data for consid-

eration.

Study designs

Six studies were classified as effectiveness studies; the

remaining eight examined the efficacy of Bti in more

controlled settings. The most common study design was

the NRCT, which was used in 10 studies. Three were

CRCTs (4, 10, 11 in Tables 1 and 2), often considered

the ‘gold standard for such research’, and 1 was a RCT

(13 in Table 1). Eight studies used various breeding con-

tainers (water tanks, water jars, discarded tires, plants)as the unit of allocation, 4 used households (4, 8, 11,

12 in Table 2), and 2 used land areas (7 and 14 in

Table 2). All studies incorporated a control group, the

majority of which received only entomological surveil-

lance. Two of the control groups received education

and/or environmental management interventions (4, 11

in Table 2), and one control group received ‘standard

control strategies’ consisting of weekly temephos treat-

ment (7 in Table 2). Two control areas were unexpect-

edly treated with extensive space spraying mid-way

through the study due to a dengue outbreak (8, 14 in

Table 2).

The sample size varied significantly across studies. Thesmallest study (5 in Table 1) examined only five cement

tanks in each of the two intervention groups compared to

eight control tanks, while the largest study (4 in Table 2)

incorporated more than 1000 households. The duration

of follow-up ranged from 20 days (5 in Table 1) to

15 months (4 in Table 2) with a median follow-up of

6 weeks. Three studies (9, 10, 14 in Tables 1 and 2) pre-

specified the period of follow-up.

Nearly all studies provided a rudimentary description

of the study setting, often limited to geographical loca-

tion and previous estimates of dengue incidence. Less

commonly reported was information on potential con-

founding factors such as the socio-economic status of res-idents, housing construction and infrastructure. Weather

conditions, either historical or during the intervention

period, were reported in only five studies (4, 7, 10, 11,

12 in Tables 1 and 2).

Outcome measures

The most commonly reported outcome measures in the

efficacy studies were larval and pupal densities, defined as

the mean number of larvae or pupae per container, and

per cent reduction in infestation using Mulla’s formula

(Mulla et al. 1971). Four studies (6, 9, 12, 14 in Tables 1

and 2) also monitored the ‘average larval free period’ orthe amount of time after application of the intervention

that potential habitats remained free from Aedes larvae.

In the community effectiveness trials, oviposition indices

and the Stegomyia indices (the house index (number of

positive houses per 100 houses), container index (number

of positive containers per 100 containers) and Breteau

index (number of positive containers per 100 houses))

were more commonly reported (WHO/SEARO 1999).

Only one study reported clinical outcomes from routinely

collected epidemiological data (14 in Table 2).

Entomological surveillance protocols were clearly

reported in 10 of the studies, while four studies (2, 4, 6,

13 in Tables 1 and 2) provided no or limited informationregarding entomological sampling methods. Five studies

(1, 2, 3, 5, 9 in Table 1) did not incorporate statistical

precision estimates or significance tests in the reporting of

outcomes.

Interventions

A wide range of formulations and application methods

were utilised in the studies. Seven studies (2, 4, 6, 9, 10,

11, 12 in Tables 1 and 2) incorporated slow-release Bti

tablets or briquettes, seven studies (1, 3, 5, 7, 8 14 in

Tables 1 and 2) used manual or motorised spray equip-

ment to apply Bti, and three studies (2, 8, 13 in Tables 1and 2) applied Bti granules or powder directly into posi-

tive breeding sites. The majority of the efficacy trials uti-

lised only a single application of Bti in the study

containers. In contrast, all of the effectiveness trials

repeated application of Bti in differing frequencies as out-

lined in Table 2. Seven studies incorporated multiple

intervention groups, comparing the effect of various for-

mulations or dosages of Bti (1, 2, 5, 6 in Table 1) or






Table 1 Summary of efficacy studies evaluating the use of Bti for the control of dengue vectors

No. Reference Setting Objectives

Study design

and duration Bti formulation Intervention group(s)

1. Ansari and

Razdan

(1999)

D el hi, I nd ia E val ua te t he Bt H-14

granule formulation

under laboratory and

field conditions

against Aedes aegypti

NRCT

4 weeks

Bti H-14 granules

Potency not reported

Manufacturer not reported

Single spray

application

of Bti H-14 applied to

20 evaporation

coolers and 36

discarded tires at

three different doses

(0.25, 0.50 and

1.0 g/m2)

2. Batra et al.

(2000)

D el hi, I nd ia E val ua te t he

effectiveness of 3

formulations of Bti

against immature

A. aegypti in coolers

and tires

NRCT

6 weeks

Bacticide (1000 ITU/mg)

Biotech International, Delhi

Vectobac DT (1900 ITU/mg)

Vectobac G (3500 ITU/mg)

Abbott Laboratories

Single application

of Bti in 5 different

formulations/doses:

(1) 15 desert coolers

with Vectobac

G at 2 g/cooler

(2) 65 desert

coolers with

Vectobac DT at

0.75 g/cooler(3) 10 desert

coolers with

Bacticide powder

at 1.0 g/cooler

(4) 35 discarded tires

with Vectobac DT

at one tablet

(0.375 g) per tire

(5) 20 discarded tires

with Vectobac DT at

two tablets

(0.75 g) per tire

3. Dua et al.

(1993)

Hardwar,

India

Evaluate Bactoculicide

for its efficacy to

control mosquitos

(Aedes, Anopheles,

Culex) breeding in

factory scraps in anindustrial area

NRCT

6 weeks

Bactoculicide

Potency not reported

Bordsk Chemical,

Moscow

Single application of

Bactoculicide

sprayed over the

standing water in

73 industrial

scrap containerspositive for mosquito

larvae

at a dosage of 0.5 g/m2

5. Haq et al.

(2004)

Surat City,

India

Evaluate spraying of

two bacterial larvicide

formulations for

efficacy against

Anopheles, Culex and

Aedes mosquitoes

under the operational

conditions of an urban

malarial control

programme

NRCT

20 days

Bacticide

WP (1000 ITU/mg)

Biotech International,

Delhi

Vectobac 12AS

(1200 ITU/mg)

Aventis Crop

Sciences

(1) Bacticide sprayed

at 5 kg/ha in 5

cemented tanks and

chambers at

15 construction sites;

retreatment at 10 days

(2) Vectobac

sprayed at 11 kg/ha

in 5 cemented

tanks and chambers

at 16 construction sites;

retreatment at 10 days






Control group(s)

Principal outcomes and

statistical analysis Results Study conclusions

No treatment of

4 evaporation

coolers and

6 discarded tires

Larval density and

per cent reduction

(Mulla)

No statistical testing

of results

Reduction at 4 weeks:

Evaporation coolers:

0.25 g/m2= 46.3%

0.5 g/m2= 100%

1.0 g/m2= 100%

Discarded tires:

0.25 g/m2= 47.7%

0.5 g/m2= 100%

1.0 g/m2= 100%

The formulation was most

effective at a dose of 0.5 g/m2

with larvicidal activity persisting

for up to 4 weeks. Bt H-14 may be

used for control of dengue,

but studies examining relative

efficacy and cost-effectiveness

are required

No treatment

of 10 desert

coolers

Per cent of breeding

sites positive for

3rd/4th stage instars

and pupae; per cent

reduction (Mulla)


of results

Per cent reduction

Intervention 1: Vectobac

G 2 weeks = 100%

4 weeks = 66.7%

6 weeks = 16.7%

Intervention 2: Vectobac DT

2 weeks = 100%

4 weeks = 86.5%

6 weeks = 28.8%

Intervention 3: Bacticide2 weeks = 100%

4 weeks = 25.0%

6 weeks = 12.5%


2 weeks = 100%

4 weeks = 60.9%

6 weeks = 6.3%


2 weeks = 100%

4 weeks = 100%

6 weeks = 0%

Results showed that Bti

formulations provide complete

control of A. aegypti

larvae for 2 – 4 weeks. Study

highlights the practical

community-based

application of Bti.

Use of these formulations is

effective and more

user-friendlythan conventional methods

No treatment of

10 industrial

scrap containers

positive for

mosquito larvae

Larval density of

3rd/4th stage instars,

per cent reduction

(Mulla)


of results

Per cent Reduction:

24 hrs: 100%

10 days: 100%

14 days: 97.7%

24 days: 98.4%

5th week: 100%6th week: 90%

Bactoculicide appeared to

be the best solution for

controlling mosquito breeding

in such problematic habitats,

controlling mosquito breeding

for up to 5 weeks

No treatment of

8 cemented

tanks and

chambers at

15 construction

sites

Pupal/larval densities

and per cent

reduction

(Mulla)

No statistical

testing

of results

(1) Bacticide provided 100%

reduction for duration

of the study

(2) Vectobac provided 100%

reduction through day 3; 53.1%

reduction on day 17 after

retreatment

Study demonstrated that

biolarvicides should be used

at an interval of 7 – 10 days.

Liquid Vectobac had a relative

ease of operation compared

to Bacticide. Biolarvicides

can be incorporated

as part of integrated vector

control program






Table 1 (Continued )


Study design

and duration Bti formulation Intervention group(s)

6. Kroeger et al.

(1995)

Cucuta,

Columbia

Three objectives: (1)

describe people’s

knowledge, attitudes and

practices regarding

dengue fever, (2) analyse

infestation of the

community with

A. aegypti and (3) test

the efficacy of Bti with

respect to the level and

duration of larval

reduction in water tanks

NRCT

48 days

Culinex tablets

(33 000 ITU/mg)

Valent BioSciences 2 tablets of Culinex

(33 000 ITU/mg)

per 50 l in 143 household water

tanks used for laundry

1 tablet of Culinex

(33 000 ITU/mg)

per 50 l in 6 household

water tanks used for laundry

2 tablets of Culinex

(33 000 ITU/mg) per 50 l in

61 household watertanks used for laundry


(33 000 ITU/mg) per 50 l in

11 household water tanks

used for laundry that were

regularly emptied during

first 10 days of observation

9. Mahilum

et al. (2005)

Cebu City,

Philippines

Evaluate the present

dengue situation and

control strategies to

include a survey of

mosquito breeding zsites

and infestation rates, an

evaluation of people’sknowledge, attitude and

practices towards

dengue infection and the

efficacy of Bti tablets

against A. aegypti larvae

NRCT

21 days

Vectobac DT/Culinex

tablets (2700 ITU/mg)

Valent BioSciences

11 positive breeding sites,

including drums, pails,

cement basins, discarded tires

and water jars, were treated

at a single application of

1 tablet for sites <50 l capacity

and 2 tablets for sites >50l capacity

10. Marcombe

et al. (2011)

Vauclin,

Martinique

Characterise the

resistance status of

A. aegypti larvae from

Martinique to

conventional and

alternative insecticides

and to assess their

efficacy and residual

activity under simulated

and field conditions

CRCT

105 days

Vectobac DT

(3400 ITU/mg)

Abbott Laboratories

Three communities each had 5

positive breeding sites selected

for a single treatment with one

of 4 insecticides: Bti (5 mg/l),

diflubenzuron, pyriproxyfen

or spinosad, for a total of

15 interventions sites

per insecticide

13. Sulaiman

et al. (1999)

Kuala

Lumpur,Malaysia

Compare the efficacy of

Abate (temephos) andVectobac G against

Aedes albopictus in

bromeliads in the field.

RCT

4 weeks

Vectobac G

(200 ITU/mg)Abbott Laboratories

Forty-five bromeliad plants chosen

at random and divided into3 groups of 15 plants assigned

to receive a single application

of either (1) Vectobac G at 1 g

per plant, (2) Abate at 1 g per

plant or (3) no treatment

Bti, Bacillus thuringiensis israelensis; RCT, randomised controlled trials; CRCT, cluster-randomised controlled trials; NRCT,

non-randomised controlled trials.






Control group(s)

Principal outcomes and

statistical analysis Results Study conclusions

(1) Culinex vs. no

larvicide

Length of time until tank

reinfested with 3rd or 4th

larval instar

Wilcoxon rank-sum test and

chi-square test

Intervention 1:

>90% of treated tanks remained free of

reinfestation for 30 days, compared to <30%

of untreated tanks (no P-value reported)

Application of Bti led to a rapid and total elimination of

mosquito larvae with an effect that lasted for more than a

month. Lower doses were less efficacious and should not

be recommended. Community acceptance of Bti was

higher than that of temephos, largely because of the lack

of effect on water quality and taste. Further studies are

required to evaluate the relative reliability and costs

compared to traditional larvicides

No treatment of 22

household water tanks

used for laundry

(2) Culinex (33 000

ITU/mg) vs. Culinex

(8000 ITU/mg)

Intervention 2:

100% of 33 000 ITU treated tanks free of

reinfestation for 28 days, compared to only

6 days in those tanks treated with 8,00 ITU

formulation (P = 0.025)

1 tablet of Culinex

(8000 ITU/mg) per 50 l

in 20 household water

tanks used for laundry

(3) Two vs. one tablet

of Culinex

(33 000 ITU/mg)

per tank

Intervention 3:

100% of tanks treated with 2 tablets free of

reinfestation for 28 days, compared to only

6 days in tanks treated with only 1 tablet

(P = 0.02)1 tablet of Culinex

(33 000 ITU/mg) per

50 l in 60 householdwater tanks used for

laundry

(4) Effect of changing

water

Intervention 4: 100% of tanks in both

groups free for 10 days; >90% of tanks in

both groups free for 28 days with decrease to

approximately 50% at 34 days in tanks that

are not emptied; slightly higher proportion of

emptied tanks free at all time periods

(P < 0.01)


(33 000 ITU/mg) per

50 l in 39 household

water tanks used for

laundry that were not

emptied during first ten

days of observation

Three positive breeding

sites including a 200-l

drum, a 25-l can and a

200-l plastic container

received no treatment

Mortality rates of larvae

observed at 3-day intervals

No statistical testing of results

Control sites were infested throughout the

duration of the study, while the intervention

sites showed 100% mortality for the initial

6 days of the study. Reinfestation was noted

in some containers as early as 9 days, but the

majority of containers remained free of

larvae for up to 18 days

Duration of Bti efficacy was less in field conditions than

under semi-field conditions, perhaps due to heavy rains. Bti

should be incorporated in integrated mosquito control

programmes and is a useful supplement or replacement for

conventional insecticides

3 communities each

had 5 positive breeding

sites to serve as an

untreated control (15

total)

Larval and pupal density;

relative density (Mulla)

Log transformation and ANOVA

There was a strong and significant difference

over time between treatment groups

(P < 0.001). Bti demonstrated a fast killing

effect with RD decreasing from 100% to 1%

(95% CI 0.4 – 4%), but low residual activity

with larval densities returning to 22% (95%

CI 7 – 49%) of initial size after 28 days

A lower residual activity for all insecticides in field trials

compared to semi-field trials was observed. The poor

efficacy of Bti may render control of A. aegypti

populations in Martinique difficult. Mosquitos were,

however, fully susceptible to Bti despite more than

12 years of use

Fifteen plants assigned

to the no treatmentgroup

Per cent mortality of immatures

ANOVA

Vectobac G yielded 97.8% mortality 24 hrs

after treatment, 76.2% 1 week aftertreatment and 65.4% 2 weeks after

treatment. This reduction was not

significantly different from Abate (P > 0.05),

but was significantly different from the

control (P < 0.01). After 2 weeks, there was

no significant differences between the

intervention and control groups

Both insecticides would be effective in a similar

environment with residual activity of up to 1 week






Table 2 Summary of effectiveness studies evaluating the use of Bti for the control of dengue vectors


Study design and

duration Bti f or mu la ti on I nt er ve nt io n g ro up (s )

4. Favier et al.

(2006)

Brazilia, Brazil Determine the influence of climate

and of environmental vector

control with or without insecticide

on Aedes aegypti larval indices and

pupal density

CRCT

18 months

Mosquito Dunks (7000

ITU/mg)

Summit Chemical

Four intervention groups, each containing

environmental management plus:

(1) Temephos (Abate) at 1 ppm in

all containers

(2) Temephos (Abate) at 1 ppm in all

containers in all premises

(3) Bti (Mosquito Dunks) in all

containers in positive premises only

(4) Methoprene-S (Altosid) in all

containers in positive premises only

7. Lam et al.

(2010)

Western

Singapore

Investigate the efficacy of Bti

against Aedes albopictus in a

forested military training ground

where source reduction in natural

breeding sites is difficult and non-

specific insecticides may cause

harm to the ecosystem

NRCT

3 months

Vectobac WG (3000 ITU)

Valent BioSciences

130 ha sprayed with Bti at a dosage of

500 g/ha every 2 weeks using motorised

back-pack and vehicle-mounted sprayers

8. Lee et al.

(2008)

Selangor State,

Malaysia

Determine the impact of larviciding

with a Bti formulation, Vectobac

WG, on the adult mosquito

population in a dengue endemic

site in Selangor State, Malaysia

NRCT

12 weeks

Vectobac WG

(3000 ITU/mg)

Valent BioSciences

Two residential areas (20 houses each)

received a single indoor treatment of

Vectobac WG in all water containers

>50 l at a dosage of 8 mg/l combined

with back-pack spraying of all outdoor

larval habitats at a dosage of 500 g/ha

every 2 weeks

1 1. O cam po

et al. (2009)

Cali, Columbia Evaluate two control methods for

A. aegypti that can be used by the

community: lethal ovitraps and Bti

briquettes

CRCT

4 months

Bactimos briquettes

(7000 ITU/mg)

Summit Chemicals

Four neighbourhoods, each had one

block (40 houses) randomly selected to

receive education and either (1) lethal

ovitraps, (2) Bti briquettes in main

breeding sites, (3) lethal ovitraps + Bti

briquettes or (4) no insecticide (control);

Bti dosage was 1/4 briquette in each

water storage tank (76 total), which

were replaced monthly

12. Phan-Urai

et al. (1995)

Chanthaburi

Province,

Thailand

Evaluate the Bti H-14 formulated

tablet for Aedes larvae in a rural

village of Chanthaburi Province

NRCT

17 weeks

Larvitab 1-g tablet

(600 ITU/mg)

Manufacturer

not reported

Bti at a dosage of 1 g per 200 l was

applied to all potential breeding sites,

including water storage containers,

cement baths and ant guards, in a single

village (61 houses) in Chanthaburi

Province. Treatment was repeated when

containers were reinfested with mosquito

larvae

14. Tan et al.

(2012)

Shah Alam,

Malaysia

Comparing the efficacy of BTI

(Vectobac) against Aedes

albopictus and A. aegypti

RCT

1 year

Vectobac WG

(3000 ITU/mg)

Valet Biosciences

Corporation

One residential area (300 houses) received

7 biweekly cycles of Vectobac WG,

followed by 7 weekly cycles, followed by

4 biweekly cycles in all mapped

potential and actual outdoor larval

habitats

Bti, Bacillus thuringiensis israelensis; RCT, randomised controlled trials; CRCT, cluster-randomised controlled trials; NRCT,

non-randomised controlled trials.






Control group(s)

Principal outcomes and statistical

analysis Results Study conclusions

Only environmental

management, defined as

incitation to container

removal when possible or

emptying water

in storage containers

in all premises

House index, container index,

Breteau index, pupal density

Nonparametric tests with 95% CI

for indices and Mann – Whitney

U -test for proportions

No significant differences in larval indices

and pupal density between control and

intervention groups

In moderately infested areas, insecticides do not

improve upon environmental vector control.

Infestations could be further reduced by focusing on

residences and containers particularly at risk

128 ha treated with

standard control

strategies comprised of

weekly oiling of ground

larval habitats and

monthly treatment of

permanent water bodies

with temephos

Ovitrap index, larval density,

per cent reduction (Mulla)

t -test for OI and larval density

Per cent reduction in ovitrap index at

intervention site:

Month 1 = 14.2% (P < 0.05)

Month 2 = 47.9% (P < 0.05)

Month 3 = 66.0% (P < 0.05)

Per cent reduction in larval density at

intervention site:

Month 1 = 59.3% (P < 0.05)

Month 2 = 53.2% (P < 0.05)Month 3 = 80.0% (P < 0.05)

Wide application of Bti into vegetation to treat all

natural breeding sites produced a significant decline

of the adult A. albopictus population compared to

the control This is an innovative approach that can

be easily adapted to all communities to successfully

suppress the A. albopictus adult population

One untreated residential

area that was treated with

extensive space spraying

6 weeks into the trial due

to a dengue outbreak

Ovitrap index and larval density

t -test for OI and larval density

The OI significantly decreased in both study

sites 4 weeks after initiating the

intervention, declining from 57.5% to

19.1% (P < 0.05) at one site and 66.7% to

30.3% (P < 0.05) at another. This decline

in the OI was paralleled by a similar decline

in both A. aegypti and Aedes albopictus

larval densities. An increase in OI and larval

density was observed in both

sites following cessation of the

intervention. The OI at the control site

remained high until the initiation of

space spraying following a dengue outbreak

Widespread application of Vectobac WG at targeted

larval habitats is able to provide control of dengue

vectors. Space spraying of Bti was found to be

superior to traditional methods of application in

terms of effectiveness, coverage and labour.

Additionally, Bti did not produce any undesirable

environmental consequences

One block from each of

the 4 neighbourhoods

was randomly selected to

receive no insecticide,

but only education

(environmental control,

emptying water jars)

House index, pupal index (mean

pupae per house) and adult index

(per cent of houses infested with

adult Aedes)

Poisson regression

Entomological indices obtained during the

intervention period were not significantly

different between treatment groups and

controls. During the entire study period

(341 visits), only one water tank treated

with Bti was positive for larvae. Positive

containers consisted mostly of plants in

water and small containers. Bti briquettes

were not used routinely in 40% of houses

Pre-intervention education and environmental

management may have contributed to the lack of

effect seen with interventions. Decrease in pupal

density did not eliminate presence of adult

mosquitoes in homes to a level sufficient to prevent

transmission suggesting larger buffer zone may be

required to address breeding sites outside of the

residential areas. Use of Bti briquettes may have

induced people to change water more often

No treatment of similar

breeding sites in a single

village (92 houses) in

Chanthaburi province.

House index, container index,

Breteau index, per cent reduction

(Mulla), average larva free period,

landing and biting rates

F -test, t -test

Significant reductions (P < 0.05) in the

intervention area were observed, with

averages of:

HI = 69.8%

CI = 84.1%

BI = 84.4%

Landing rate = 73.9%

Biting rate = 73.6%

No similar trend observed in control area.

Average larval free period was longest in

drinking containers (16.4 + / 2.5 weeks),

followed by ant guard, washing and bathingcontainers

The Bti formulation was very practical and effective

for the control of A. aegypti larvae in Thai

communities. The intervention was readily accepted

by the community

One residential area

without BTI application.

However, intensive

pyrethroid fogging

operation in study weeks

37 – 54 due to a dengue

outbreak

Ovitrap index and larval density

Routine epidemiological data on

dengue cases

Chi-square test for OI

t -test for larval density

OI was suppressed to below 10% and

maintainted up to 4 weeks post-treatment

Outdoor OI remained at 40% in the

untreated site (P < 0.05)

1 dengue case in the treated area

15 dengue cases in the untreated area

BTI application can suppress A. aegypti and Aedes

albopictus populations at a dengue endemic site with

a temephos-resistant population and potentially

interrupt dengue transmission in humans






comparing the effect of Bti to other insecticides (4, 10 in

Tables 1 and 2) or lethal ovitraps (11 in Table 2) with a

standard control. The most common insecticide of com-

parison was temephos, which was used in two of the

studies (4, 10 in Tables 1 and 2).

Efficacy and effectiveness of Bti interventions

Each of the eight efficacy studies reported a post-inter-

vention reduction in the observed density of immature

stages compared to the respective control group. In gen-

eral, these were non-randomised studies using containers

as the unit of allocation. In the community-based effec-

tiveness studies, the results were less clear, with 4 of the

6 studies (7, 8, 12, 14 in Tables 1 and 2) reporting signif-

icant but time-limited reductions in entomological indi-

ces. The two effectiveness studies that did not show

significant reductions employed basic interventions suchas environmental management (4 in Table 2) or general

education on environment control practices (11 in

Table 2), in the respective control groups. The other

study that used standard dengue vector control practices

as the control comparison (7 in Table 1), did, however,

report a relative reduction in entomological indices in the

Bti intervention area.

In the efficacy studies looking only at targeted breeding

sites, Bti demonstrated a rapid killing effect, typically

eliminating all larvae from treated containers within

24 h. The vast majority of containers remained free of

larvae for the first 2 weeks of observation. However,

reinfestation of some containers did occur within 7 –

9 days of treatment (5, 9 in Table 1). Only one study (3

in Table 1) reported 100% reduction in larval density for

more than 4 weeks with a single application of Bti. Simi-

lar results were demonstrated in another study (1 in

Table 1), but the study period was limited to 4 weeks.

Five studies examined the effect of repeated Bti treat-

ments (7, 8, 11, 12, 14 in Table 2). Two of these studies

sprayed Bti every 2 weeks (7, 8 in Table 2), in 1 study,

Bti briquettes were replaced every month (11 in Table 2),

in another study, Bti briquettes were replaced when the

containers were reinfested (12 in Table 2), and in 1 study

(14 in Table 2), Bti was sprayed in biweekly and weekly

cycles. In four of the studies (7, 8, 12, 14 in Table 2), therepeated application of Bti at various frequencies resulted

in significant (P < 0.05) reductions in the density of

immature stages compared to the control over the course

of treatment. Each of these four studies also examined

the effect on adult dengue vector populations, either

through ovitrap indices or landing and biting rates. In

each study, a decline in the adult mosquito population

was observed, typically only after the second application

of Bti, which occurred in the fourth to sixth week of the

trial. This delayed effect is thought to be due to the sur-

vival of already existing adult mosquitoes, which would

not have been affected by larvicidal applications of Bti.

The study by Lee et al. (8 in Table 2) showed a reboundin the adult and larval indices within 6 weeks of cessa-

tion of treatment. Although the study by Ocampo et al.

(11 in Table 2) did not observe any significant reductions

in entomological indices, only one Bti-treated container

was ever found to be positive for mosquito larvae.

The four studies that compared different formulations

of Bti (1, 2, 5, 6 in Table 1) did not suggest evidence of

superior efficacy of any one commercial product. The

results did, however, suggest that higher doses of Bti pro-

vide a longer duration of effect (1, 2, 6 in Table 1). The

per cent reduction in the density of immature stages at

4 weeks nearly doubled with a proportional increase in

Bti concentration in these three studies. The study by An-sari and Razdan (1 in Table 1) demonstrated the decreas-

ing marginal benefit of this approach, as both of the

higher concentrations used (0.5 and 1.0 g/m2) achieved

similar results at 4 weeks, suggesting that a similar effect

could be achieved with less cost at the lower dose.

In the two studies where Bti formulations were com-

pared with other insecticides (4, 10 in Tables 1 and 2),

the results were mixed. The study by Favier et al. (4

Table 2) found no significant reductions attributable to

any of the interventions, which included Bti, temephos

and methoprene-S. Here, the authors concluded that

insecticides may not improve on environmental control

practices, which served as the control comparison. Incontrast, the study by Marcombe et al. (2011) showed

that both Bti and pyriproxyfen were effective in initially

lowering larval densities but had a notably lower residual

activity compared to diflubenzuron and spinosad.

Only one study (14 in Tables 1 and 2) linked routinely

collected epidemiological data to the entomological data.

When a dengue outbreak occurred in the study area, only

one case was reported in the Bti intervention area and 15

cases were reported in the control area, suggesting that

the lower mosquito densities in the Bti intervention area

could have had a protective effect.

Acceptability of Bti

Very few of the included studies formally evaluated the

acceptability of Bti application. The study by Haq et al.

(5 in Table 1) surveyed field staff and noted some opera-

tional challenges and reports of skin irritation after con-

tact with Bacticide. Lee et al. (8 in Table 2) monitored

for potential effects on non-target organisms, but did not

observe any undesirable consequences. Ocampo et al.






(11 in Table 2) reported that the Bactimos briquettes left

a visible residue on water storage containers and specu-

lated that this may have induced residents to clean the

containers more often.

In general, most studies reported that the Bti interven-tion was readily accepted and even preferred over other

measures such as temephos applications because it did

not affect water quality or taste. The study by Ocampo

et al. (11 in Table 2) was the only one to quantify accep-

tance, reporting that 40% of the houses did not routinely

use the briquettes, because householders did not like the

residue the briquettes left in their water.

Discussion

The evidence presented from the efficacy studies suggests

that Bti can be effective in controlling the immature

stages of dengue vector mosquitoes in a variety of breed-ing sites. The killing effect is rapid, typically eliminating

all immature forms from treated containers within 24 h,

with a residual effect that ranges between 2 and 4 weeks.

These results, however, only suggest that Bti is effective

in specifically targeted containers that actually receive

treatment. Given the large number of potential habitats,

the widespread application of Bti to all potential breeding

sites may not be practical.

A better estimate of the overall impact of Bti as single

agent is provided by the effectiveness studies (4, 7, 8, 11,

12, 14 in Table 2). The findings from these studies are

mixed and do not provide conclusive evidence that Bti,

when used a single agent, produces significant reductionsin entomological indices. There are a number of reasons

that might explain the lack of effect. First, investigators

may have failed to identify and treat all potential breed-

ing sites within each household. Thus, while Bti may

have achieved significant reductions in treated containers,

the existence of even a few untreated and productive

breeding sites may have masked the effect of Bti. The

study by Ocampo et al. (11 in Table 2) highlights this

phenomenon, where over the course of the study, only

one of 76 water storage tanks that were treated with Bti

was ever positive for mosquito larvae. However,

untreated smaller containers and containers holding

aquatic plants were often positive for larvae.The comparison of experimental results with untreated

control groups is also important in determining the

impact of Bti as a sole control agent. In all studies where

individual containers were the unit of allocation, the con-

trol containers received no treatment. However, in 2 of

the 4 household and community-level studies (4, 11 in

Table 2), the control group received an intervention in

the form of education and/or environmental management.

Both these studies found no significant differences

between the Bti intervention groups and the control

groups, suggesting that Bti alone provided an equivalent

level of control as what was achieved through education

and/or environmental management.The study by Ocampo et al. (11 in Table 2) also raised

the issue of buffer zones. While it may be possible to

greatly reduce breeding sites within targeted residential

areas, treatment must also extend beyond these areas to

prevent the immigration of adult mosquitoes from non-

treated areas. The flight range of A. aegypti is restricted:

mosquitoes rarely disperse further than 100 m from their

emergence location (Muir & Kay 1998; Harrington et al.

2005). Despite this limited flight range, Ocampo et al.

(11 in Table 2) did not observe a reduction in the pres-

ence of adult mosquitoes in the intervention households.

This result suggests that their buffer zone, which con-

sisted of treatment of one house beyond the interventionblock in every direction, was insufficient. Lee et al. (8 in

Table 2) experienced a similar challenge because they

were unable to treat a factory that was adjacent to one

of their study sites. While they still observed a reduction

in the ovitrap index at this location, the magnitude of the

effect was less pronounced than that of another site,

which was not adjacent to the untreated factory.

The reviewed studies did not provide a generalisable

estimate of community acceptance and uptake of the Bti

interventions. In the majority of the studies, vector sur-

veillance and Bti application were carried out by the

investigators rather than vector control authorities or

members of the community. Given the limits on nationalbudgets for vector control programmes, it is unlikely that

routine control efforts will achieve levels of intensity

comparable to those obtained in these studies.

The majority of the studies failed to assess and com-

pare baseline characteristics between the control and

intervention groups. Additionally, five studies (1, 2, 3, 5,

9 in Table 1) did not incorporate any statistical methods

into their data analyses for the purpose of estimating pre-

cision or comparing results between groups. Without this

information, it is difficult to interpret the significance of

the reported results.

Finally, only one study (14 in Table 2) linked routinely

collected epidemiological data from both the Bti interven-tion and control sites. Although fewer dengue cases were

reported in the intervention area, no information was

available regarding the method or quality of routine epi-

demiological data collection or possible sites of dengue

infection outside of the study area.

Publication bias should be considered as a final limita-

tion of this study, as likely more studies with a positive

outcome are reported in the literature. The diversified






search strategy limits this publication bias; however, it

cannot be completely eliminated.

In summary, there is evidence that Bti is effective in

reducing the density of immature dengue vectors when it

is applied to targeted containers as demonstrated by theefficacy studies. However, the evidence to suggest that

Bti is effective as a single agent, when used in a commu-

nity setting, is limited. Given the increasing prevalence of

insecticide resistance in dengue vectors in many parts of

the world, understanding the control implications of

using alternatives to chemical insecticides such as Bti is

becoming increasingly important. However, there is a

clear need for further studies that utilise cluster-rando-

mised controlled designs to investigate the efficacy and

effectiveness of Bti and to further link entomological out-

comes to dengue transmission measures.

References

Goldberg L & Margalit J (1977) A bacterial spore demonstrating

rapid larvicidal activity against Anopheles sergentii, Uranotae-

nia unguiculata, Aedes aegypti, Culex pipiens, Culex univitat-

tus. Mosquito News, 37, 355 – 358.

Harrington C, Scott T, Lerdthusnee K et al. (2005) Dispersal of

the dengue vector Aedes aegypti within and between rural

communities. American Journal of Tropical Medicine and

Hygiene 72, 209 – 220.

Harris A, Rajatileka S & Ranson H (2010) Pyrethroid resistance

in Aedes aegypti from Grand Cayman. American Journal of

Tropical Medicine and Hygiene 83, 277 – 284.

Lacey L (2007) Bacillus thuringiensis serovariety israelensis and

Bacillus sphaericus for mosquito control. Journal of the Amer-

ican Mosquito Control Association 23, 133 – 163.

Lacey L & Mulla M (1990) Safety of Bacillus thuringiensis

(H-14) and Bacillus sphaericus to non-target organisms in

the aquatic environment. In: Safety of Microbial Insecticides

(eds M Laird, L Lacey & E Davidson) CRC Press, Boca

Raton, pp. 169 – 188.

Lee B & Scott G (1989) Acute toxicity of temephos, fenoxycarb,

diflubenzuron, and methoprene and bacillus thuringiensis var.

israelensis to the mummichog (Fundulus heteroclitus). Bulletin

of Environment Contamination and Toxicology 43, 827 – 832.

Liberati A, Altman D, Tetzlaff J et al. (2009) The PRISMA state-ment for reporting systematic reviews and meta-analyses of

studies that evaluate health care interventions: explanation

and elaboration. PLoS Medicine 6, e1000100.

Merritt R, Walker E, Wilzbach M, Cummins K & Morgan W

(1989) A broad evaluation of B.t.i. for black fly (Diptera:

Simuliidae) control in a Michigan river: efficacy, carry and

nontarget effects on invertebrates and fish. Journal of the

American Mosquito Control Association 5, 397 – 415.

Mittal P (2003) Biolarvicides in vector control: challenges and

prospects. Journal of Vector Borne Diseases 40, 20 – 32.

Muir L & Kay B (1998) Aedes aegypti survival and dispersal

estimated by mark-release-recapture in northern Australia. Amer-

ican Journal of Tropical Medicine and Hygiene 58, 277 – 282.

Mulla M, Norland R, Fanara D, Darwazeh H & Mckean D

(1971) Control of chironomid midges in recreational lakes.

Journal of Economic Entomology 64, 300 – 307.

Rodriguez M, Bisset J, De Armas Y & Ramos F (2005) Pyre-

throid insecticide-resistant strain of Aedes aegypti from Cuba

induced by deltamethrin selection. Journal of the American

Mosquito Control Association 21, 437 – 445.

Saik J, Lacey L & Lacey C (1990) Safety of microbial control

agents to domestic animals and vertebrate wildlife. In: Safety

of Microbial Insecticides (eds M Laird, L Lacey & E David-

son) CRC Press, Boca Raton. pp. 115 – 131.

WHO/ TDR (2007) Special Programme for Research and Train-

ing in Tropical Diseases/World Health Organization. Report

of the Scientific Working Group meeting on dengue. Dengue

Bulletin, 31, 183 – 186.

WHO/ TDR (2007) Special Programme for Research and Train-

ing in Tropical Diseases/World Health Organization. Dengue:

Guidelines for Diagnosis, Treatment, Prevention, and Control.

World Health Organization, Geneva.

WHO/SEARO (1999) Prevention and Control of Dengue and

Dengue Haemorrhagic Fever: Comprehensive Guidelines.

WHO Regional Office for Southeast Asia, New Delhi.

Cited References

Ansari M & Razdan R (1999) Laboratory and field evaluation of

Bacillus thuringiensis H-14 (Bt. H-14) granule formulation

against Aedes aegypti in Delhi, India. Dengue Bulletin 23, 94 – 98.

Batra C, Mittal P & Adak T (2000) Control of Aedes aegyptibreeding in desert coolers and tires by use of Bacillus thuringi-

ensis var. israelensis formulation. Journal of the American

Mosquito Control Association 16, 321 – 323.

Dua V, Sharma S & Sharma V (1993) Application of Bactoculi-

cide (Bacillus thuringiensis H-14) for controlling mosquito

breeding in industrial scrap at BHEL, Hardwar (U.P.). Indian

Journal of Malariology 30, 17 – 21.

Favier C, Degallier N, Vilarinhos P, De Carvalho M, Yoshizawa

M & Knox M (2006) Effects of climate and different manage-

ment strategies on Aedes aegypti breeding sites: a longitudinal

survey in Brasilia (DF, Brazil). Tropical Medicine, Interna-

tional Health 11, 1104 – 1118.

Haq S, Bhatta R, Vaishnavb K & Yadava R (2004) Field evalua-

tion of biolarvicides in Surat city, India. Journal of Vector

Borne Diseases 41, 61 –

66.Kroeger A, Dehlinger U, Burkhardt G, Athehortua W, Anaya H &

Becker N (1995) Community based dengue control in Columbia:

People’s knowledge and practice and the potential contribution

of the biological larvicide Bti (Bacillus thuringiensis israelensis).

Tropical Medicine and Parasitology 46, 241 – 246.

Lam P, Boon C, Yng N & Benjamin S (2010) Aedes albopictus

control with spray application of Bacillus thuringiensis israel-

ensis, strain AM 65 – 52. Southeast Asian Journal of Tropical

Medicine and Public Health 41, 1071 – 1081.






Lee H, Chen C, Masri S, Chiang Y, Chooi K & Benjamin S

(2008) Impact of larviciding with a Bacillus thuringiensis

israelensis formulation, VectoBac WG, on dengue mosquito

vectors in a dengue endemic site in Selangor State, Malaysia.

Southeast Asian Journal of Tropical Medicine, Public Health39, 601 – 609.

Mahilum M, Ludwig M, Madon M & Becker N (2005)

Evaluation of the present dengue situation and control

strategies against Aedes aegypti in Cebu City, Philippines.

Journal of Vector Ecology 30, 277 – 283.

Marcombe S, Darriet F, Agnew P et al. (2011) Field efficacy of

new larvicide products for control of multi-resistant Aedes

aegypti populations in Martinique (French West Indies).

American Journal of Tropical Medicine, Hygiene 84, 118 – 126.

Ocampo C, Gonzalez C, Morales C, Perez M, Wesson D &

Apperson C (2009) Evaluation of community-based strategies

for Aedes aegypti control inside houses. Biomedica 29,

282 – 297.

Phan-Urai P, Kong-Ngamsuk W & Malainual N (1995) Field

trial of Bacillus thuringiensis H-14 (Larvitab) against Aedes

aegypti larvae in Amphoe Khlung, Chanthaburi Province,

Thailand. Journal of Tropical Medicine, Parasitology 18,

35 –

41.Sulaiman S, Pawanchee Z, Wahab A, Jamal J, Sohadi A &

Rahman A (1999) Evaluation of Abate 1-SG and Vectobac G

in bromeliads infested with dengue vector Aedes albopictus

(Skuse) in Kuala Lumpur, Malaysia. Medical Entomology and

Zoology 50, 165 – 167.

Tan A, Loke SR, Benjamin S, Lee HL, Chooi KH & Sofian-

Azirun M (2012) Spray application of Bacillus thuringiensis

israelensis (Bti Strain 65 – 52) against Aedes aegypti (L) and

Ae. albopictus Skuse populations and impact on dengue

transmission in a dengue endemic residential site in Malaysia.

Southeast Asian Journal of Tropical Medicine and Public

Health 43, 296 – 310.

Corresponding Author Olaf Horstick, Institute of Public Health, INF 324, University of Heidelberg, 69120 Heidelberg, Germany.

E-mail: [email protected]




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