EFFICACY OF ATTRACTIVE TOXIC SUGAR BAIT METHOD [ATSB] FOR ANOPHELES IN LATIN AMERICA

Amy Krystosik, MPHJanuary, 2015

Primary objective

• To test the efficacy of attractive toxic sugar baiting [ATSB] methods compared to blank control in the LA context.

Secondary objectives

• To determine the baseline population characteristics of an Anopheline species in terms of resting population; sugar feeding behaviors; and attraction to ASB.

• To measure outcomes of an ATSB according to vector density and age structure [parity].

Attractive Toxic Sugar Baiting Methods (ATSB)• Xu and Barnard, 2003

– Estimated median lethal concentrations (LC50 in %) [of boric acid] at 24-h exposure for male and female An. quadrimaculatus were 0.317% and 0.885%, respectively

• Beier et al., 2012– ATSB methods decimate populations of

Anopheles malaria vectors in arid environments regardless of the local availability of favoured sugar-source blossoms

Schematic ATSB model in experimental setting

Marshall et al. 2013

Measurements

• Density per trapping night

• Parity rates• Treatment dye visible

Mosquito Sampling

• IRB approved for P2 by NIH and National University in Bogota

• Estimate of number of mosquitoes per person

• Recommended by WHO

Human Landing Catches (HLC)

Schematic of Study sites Schematic of expected outcome

Reduce MalariaTransmission

Reduce vectorial capacity

Reduce vector density

Reduce daily mosquito survival rateReplace sugar

meal with ATSB

Parasite positive case

Mosquito uptakes parasites during blood meal

Other IVM methods: IRSS, ITNS, larvicides, source reduction

Mosquito resting, ovipositioning

Mosquito blood meal infects host (3rd gonotrophic cycle)

Asymptomatic Cases

Symptomatic Cases Mosquito

Sugar meal

Vaccine, case detection and treatment, improved housing

Case detection and treatment

Conceptual Model

Baseline Measures (2 months)

Sampling• Compare efficiency of methods

– Barrier screen method– HLC– CDC light traps

Population characteristics• Sugar-feeding behavior

– Proportion sugar-fed – Cold anthrone fructose assay (immediate

testing or stop peristalsis)

• Attraction to ASB– Proportion taking ASB – Observation of color dye

Schematic of Study DesignPopulation: 1 Anopheline specie

Number of Sites: 2 sites; treatment/control in all houses; 4 trapping houses in each site

Sample size: 380 HLC trapping days ~ 4 HLC trapping for 60 days/site

Study Duration: Four months (2 baseline and 2 experimental)

Study Hypotheses

Study Sites: selected with a stable Anopheline population

Site 2: ControlSite 1: Treatment

Collect mosquitoes: Adults Capture by 8 HLC and CDC light trap

HLC: Human Landing Catches; BSM: Barrier Screen Method

Allocation of higher density site to treatment group

4 HLC houses / site

Species Determination, dissections for parity, observation of color dye

.ATSB will reduce survival, vector density and age structure, of Anopheline species in the Latin American context, specifically a malaria endemic region of Colombia. .Treatment will not be equal Control in reducing survival, vector density, and age structure of Anopheline species in the Latin American context.Proportion of resting population which has sugar – fed will not be equal by site nor population characteristics [sex, species, parity].

Standardization of procedures

• Standardization of procedures for:– Parity Dissections– Human Landing Catches– Morphological Examinations for Taxonomy– Cold Anthrone Fructose Assay– Barrier Screen Method

Chronogram of Activities by Month

Known Potential Problems1. Fumigation in field site2. Low number of mosquitoes in field site3. Multiple species in site4. No observed treatment effect due to low

ASTB feeding5. Community support6. Environmental risks7. Number of bait stations per site8. Interaction with current control methods

Solutions1. Coordination with MOH2. Use previous baseline data to select site with stable

population 3. Use HLC to collect species of interest and taxonomy to

sort collections4. Analysis of true treatment by ATSB with dye5. Community consent during site selection and duration of

study6. IRB approval including environmental risks; use low

human toxicity insecticides; ATSB non-attractive to non-target organisms

7. Place ATSB in all houses8. Complementary control method (IVM) (e.g. ITNs and

ATSB, Stewart, 2013; Marshal 2013)

Next steps• Finalize Site

– Quibdó, Choco – An. nuneztovari• Year long stable population but logistics/safety complicated

– Lagoona Sonso, Valle – An. calderoni• Biweekly collections ongoing • Population unstable

– Punto Soldado– An. albimanus• Population peaks: Jan – May & July - August

• Collaborations for ATSB bait stations– Westham Innovations- Ongoing with Dr Graham White

• Hire and Train Technicians • CECIV (submitted Dec 1) / KSU IRB approval • Ordering of Supplies

Selected References1. Beier, J. C., G. C. Muller, W. Gu, K. L. Arheart and Y. Schlein (2012). "Attractive toxic sugar bait

(ATSB) methods decimate populations of Anopheles malaria vectors in arid environments regardless of the local availability of favoured sugar-source blossoms." Malar J 11: 31.

2. Gu, W., G. Müller, Y. Schlein, R. J. Novak and J. C. Beier (2011). "Natural Plant Sugar Sources of Anopheles Mosquitoes Strongly Impact Malaria Transmission Potential." PLoS ONE 6(1): e15996.

3. Marshall, J. M., M. T. White, A. C. Ghani, Y. Schlein, G. C. Muller and J. C. Beier (2013). "Quantifying the mosquito’s sweet tooth: modelling the effectiveness of attractive toxic sugar baits (ATSB) for malaria vector control." Malaria Journal 12(1): 291.

4. Müller, G. C., J. C. Beier, S. F. Traore, M. B. Toure, M. M. Traore, S. Bah, S. Doumbia and Y. Schlein (2010). "Successful field trial of attractive toxic sugar bait (ATSB) plant-spraying methods against malaria vectors in the Anopheles gambiae complex in Mali, West Africa." Malaria Journal 9(1): 210.

5. Xue, R.-D. and D. R. Barnard (2009). "Boric Acid Bait Kills Adult Mosquitoes (Diptera: Culicidae)." http://dx.doi.org/10.1603/0022-0493-96.5.1559.