Malaria
Conditions
Keywords
ATSB, Malaria, Kenya
Brief summary
The effectiveness of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) in western Kenya are threatened by insecticide resistance and vector behaviour changes toward early evening and outdoor biting malaria vectors. New tools to control malaria are needed to reduce and even interrupt malaria transmission. Attractive Targeted Sugar Bait (ATSB) is a promising new intervention designed to attract and kill mosquitoes, including those that IRS and LLINs do not effectively target. The ATSB 'bait stations' are A4-sized panels containing thickened fruit syrup laced with a neonicotinoid insecticide, dinotefuran, to attract and kill the foraging vectors. Entomological field trials in western Mali showed that ATSBs successfully reduce mosquito densities and longevity and thus have the potential to reduce malaria transmission. In Kenya, the investigators will conduct an open-label cluster-randomized controlled trial in 80 village clusters (40 per arm) to evaluate the effect of ATSBs on the burden of malaria. During two years, households in half of these village clusters will receive two or three ATSB bait stations per household structure on exterior walls approximately 1.8 meters above the ground. ATSBs will be replaced every six months. The primary outcome will be the incidence of clinical malaria in children aged 1-\<15 years enrolled in a prospective cohort followed monthly for about six months each during a 2-year period. Secondary outcomes include malaria infection prevalence assessed by rapid diagnostic tests through household surveys and the case burden of clinical malaria assessed by passive facility-based and community-based surveillance. The study includes entomological monitoring and nested acceptability, feasibility, and health economics studies. The stand-alone trial in western Kenya is a part of a multi-country ATSB consortium conducting similar trials in Zambia and Mali.
Detailed description
The current malaria vector control tools, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are critically important and have saved many lives. However, their effectiveness in western Kenya is threatened by insecticide resistance and vector behaviour changes toward more early evening and outdoor biting malaria vectors. LLINs and IRS specifically target indoor-biting and indoor-resting mosquitoes. Malaria vectors exhibit different behavioural characteristics that mitigate the effectiveness of vector control strategies. For example, traditionally, An. gambiae s.s. has been regarded as human-biting with late-night indoor-feeding and indoor-resting behaviours, while An. Arabiensis is found more often in drier environments and is more zoophagic with outdoor biting and resting behaviours. Following LLINs and IRS's widespread scale-up, the dominant African vectors' distributions and behaviours changed with An. gambiae s.s. and An. Funestus (also an indoor human biter) diminishing in abundance relative to An. arabiensis. Subsequently, shifts towards earlier evening biting by An. Gambiae s.s. (before people enter houses to sleep under LLINs) and later biting by An. Funestus (biting in the morning after sunrise) are examples of behavioural plasticity enabling these species to avoid contact with the LLIN and IRS insecticides. There is a need for interventions that supplement and complement LLINs and IRS by killing mosquitoes outside houses using other biologic mechanisms (e.g., targeting sugar feeding behaviour). Furthermore, insecticides are required with novel modes of action that may restore sensitivity to pyrethroids by killing both pyrethroid-resistant and sensitive mosquitoes. Attractive Targeted Sugar Bait (ATSB) (the name was recently changed from Attractive Toxic Sugar Bait to highlight that it targets malaria vectors) is a promising new intervention that potentially fills the need for outdoor interventions with novel killing effects. ATSB 'bait stations' are A4-sized panels containing thickened fruit syrup laced with a neonicotinoid insecticide (dinotefuran) to attract and kill the foraging vectors. Entomological field trials in Mali showed that ATSBs successfully reduce mosquito densities and longevity and thus have the potential to reduce malaria transmission. Large scale efficacy studies are now needed to establish the efficacy of ATSB for controlling malaria transmission.
Interventions
DEVICEAttractive Targeted Sugar Bait (ATSB)
An ATSB is a A4-sized panel containing thickened fruit syrup laced with a neonicotinoid insecticide, dinotefuran. The syrup-insecticide mixture is covered with a protective membrane that allows mosquitoes to feed through the membrane while preventing non-target organisms from feeding. This device is designed to attract and kill mosquitoes.
Sponsors
Kenya Medical Research Institute
Centers for Disease Control and Prevention
PATH
Kenya Ministry of Health
Liverpool School of Tropical Medicine
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
NONE
Intervention model description
Using restricted randomization criteria, eighty clusters will be randomized 1:1 to either the intervention arm (ATSBs deployed throughout the cluster) or the control arm. The clusters will be followed in parallel for two years. In year one the first and second cohort were enrolled and followed up over 6 months each. In year 2, the third cohort was enrolled and followed up over 1 year.
Eligibility
Sex/Gender
ALL
Age
1 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Eligibility criteria for clusters: Inclusion criteria * A grouping of contiguous rural villages in Alego-Usonga and Rarieda sub-counties of Siaya County * A minimum of 200 households Eligibility criteria for clusters:
Exclusion criteria
* Hard to reach in the rainy season * Refusal to participate by village elders Eligibility criteria for participants in the cohort study: Inclusion criteria * A resident of a household within the core area of a study cluster, defined as living in the household in the recent four months and planning to live in the same household for the next 6.5 months * Aged ≥ 1 year and \< 15 years at the time of enrollment * Written informed consent and/or assent Eligibility criteria for participants in the cohort study:
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Clinical malaria | Two years | The incidence rate of clinical malaria defined as current fever (axillary temperature of ≥37.5°C) or history of fever in last 48 hours and a positive rapid diagnostic test (RDT, pLDH or HRP2), in children aged 1-\<15 years enrolled in the cohort study |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Time to first malaria infection by PCR | Two years | The time to first malaria infection assessed by PCR in children aged 1-\<15 years enrolled in a cohort study |
| Malaria infection incidence by RDT (pLDH) | Two years | The incidence rate of malaria infection detected by RDT (pLDH) in children aged 1-\<15 years enrolled in a cohort study |
| Malaria infection prevalence by RDT (pLDH) | Two years | The prevalence of malaria infection detected by RDT (pLDH) in cross-sectional household surveys |
| Incidence of malaria illness (passive surveillance) | Two years | The incidence rate of malaria illness (sick-visit with a positive malaria rapid diagnostic test or microscopy) assessed by health-facility and community-based surveillance |
| Incidence of non-malaria illness (cohort) | Two years | The incidence rate of non-malaria illness in children aged 1-\<15 years enrolled in a cohort study |
| Prevalence of non-malaria illness | Two years | The prevalence of non-malaria illness in cross-sectional household surveys |
| Malaria vector density | Two years | Entomological outcome: Malaria vector densities |
| Proportion of female anopheles mosquitoes older than three gonotrophic cycles, | Two years | Entomological outcome: The proportion of female anopheles mosquitoes older than three gonotrophic cycles. |
| Sporozoite rate | Two years | Entomological outcomes: Sporozoite rate |
| Entomological Inoculation Rate (EIR) | Two years | Entomological outcome: Entomological Inoculation Rate (EIR) |
| Non-Target Organisms (NTOs) attracted to ATSBs | Two years | Entomological outcome: Proportion of monitoring visits where NTOs were observed on bait stations |
| Markers of insecticide resistance (dinotefuran) | Two years | Entomological outcome: Proportion of mosquitoes with resistance to dinotefuran among total mosquitoes collected in 4 WHO mosquito tubes in the trial area |
| Incidence of non-malaria illness (passive surveillance) | Two years | The incidence rate of non-malaria illness assessed by health-facility and community-based surveillance |
| Markers of insecticide resistance (deltamethrin) | Two years | Entomological outcome: Proportion of mosquitoes with resistance to deltamethrin among total mosquitoes collected in 4 WHO mosquito tubes in the trial area |
| Antibody concentrations against malaria antigen MSP-1 | Two years | Antibody concentration against merozoite surface protein-1 (MSP-1) among cohort participants |
| Antibody concentrations against malaria antigen CSP | Two years | Antibody concentration against circumsporozoite proteins (CSP) among cohort participants |
| Complexity of infection (COI) | Two years | The complexity of (malaria) infection assessed by molecular markers, including, but not limited to, 24-single-nucleotide polymorphisms (24-SNP) barcodes |
| Mosquito salivary antigens | Two years | Presence of mosquito salivary antigens in human blood as a measure for mosquito biting rates among cohort participants |
| AEs | Two years | Number of adverse events associated with misuse of ATSBs. |
| ATSB removal rate | Two years | The proportion of ATSBs that have been moved/removed |
| Perceptions of ATSBs | Two years | The proportion of household heads who perceive ATSBs as safe and effective out of all household head who consented to ATSB deployment on their household structures. |
| Household use of LLINs in the setting of ATSBs | Two years | The proportion of children aged 1-\<15 years enrolled in a cohort study who used an LLIN the night prior |
| Household care seeking behavior in the setting of ATSBs | Two years | The proportion of children aged 1-\<15 years enrolled in a cohort study who sought care for febrile illness |
| Cost-effectiveness | Two years | Incremental cost-effectiveness of ATSB above the standard of care measured through costing of intervention and efficacy outcomes |
| Markers of insecticide resistance (permethrin) | Two years | Entomological outcome: Proportion of mosquitoes with resistance to permethrin among total mosquitoes collected in 4 WHO mosquito tubes in the trial area |
Countries
Kenya
Outcome results
None listed