Topical and spatial repellents: where are we?

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Erik Garrison
5 years ago
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1 Topical and spatial repellents: where are we? 5th Outdoor Malaria Transmission Work Stream Meeting Wednesday 30th January :00-15:00 Sarah J Moore, LSHTM and Ifakara Health Institute

2 Benefits of outdoor and early evening feeding when people have intra-domicillary control tools Host availability Inter-specific larval competition 1

3 SOUTH AMERICA Average 45.8% biting before bed-time Average 66% outdoor feeding 2

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5 MEKONG REGION Average 38.5% biting before bed-time Average indoor : outdoor ratio 0.9 and 0.6 if you exclude An. minimus A 4

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7 Occupational exposure 6

8 Transient non-immunes 7

9 Vectorial capacity: a means of conceptualising the impact and mode of action of an intervention m number of mosquitoes per person p probability of daily vector survival C=ma 2 b p n / -ln p n duration of the extrinsic incubation period in days b Vector competence ma 2 the number of bites/man/day a probability a vector feeds on a host 8

RCTs >Cohort and case control trials >cross-sectional and observational studies with local populations > cross-sectional and observational of travellers.

10 RCTs >Cohort and case control trials >cross-sectional and observational studies with local populations > cross-sectional and observational of travellers. Outcomes - parasite rates of disease measured by standard methodology e.g. blood smears or rapid diagnostic tests for malaria. Risk of bias and confounding: design, recruitment methodology, generation of treatment allocation, randomization of treatments, allocation concealment, blinding, implementation of study and reporting of results New infections in person years 9

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12 Topical repellents 11

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Repellency is used as a general term to refer to a range of insect behaviours induced by chemicals that result in a reduction in human-vector contact. 1.

16 Repellency is used as a general term to refer to a range of insect behaviours induced by chemicals that result in a reduction in human-vector contact. 1. movement away from a chemical stimulus 2. interference with host detection (attractioninhibition) 3. interference with feeding response 4. incapacitation Improving health worldwide 15

17 POINT SOURCE BUBBLE 16

18 Transfluthrin coil as a point source Point source reduced Anopheles gambiae s.s. bites to between 30% and 47% up to 10 metres from the source Protective efficacy of transfluthrin coils (0.03%) M 5M 10M Distance between coils and users (Meters) 17

19 Transfluthrin coil as a bubble Bubble effect reduced Anopheles gambiae s. s. bites by more than 90% up to 10m from the source Protective efficacy of transfluthrin coils (0.03%) m 5m 10m Distance between coils and users (Meters) 18

20 Proportion and 95% CI of Anopheles gambiae s. s. mosquitoes that fed after exposure to gold standard mosquito coils Proportion (+CI) of blood fed Anopheles gambiae s. s No coil Transfluthrin coils (0.03%) 15 minutes 1 Hour 12 Hours 24 Hours Time after exposure to coils 19 19

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23 Okumu et al Comparative evaluation of combinations of long lasting insecticidal nets and indoor residual spraying, relative to the use of either method alone, for malaria vector control in an area dominated by Anopheles arabiensis. Accepted- Malaria Journal 22

24 Malaria transmission Control using existing mainstream vector control tools LLINs and IRS Evaluation of improved versions of existing vector control tools i.e. better insecticides, longer lasting nets Development of new paradigm tools to combat residual transmission occurring at times or in places where existing tools are ineffective Optimal vector management Residual Transmission Time 23

25 Improving health worldwide 24

26 Can you have community protection without killing mosquitoes? Lifetime fecundity Host availability 25

27 Why not use repellents in situation-appropriate format for public health? 26

Malaria DR. AFNAN YOUNIS

Malaria DR. AFNAN YOUNIS Objectives: Epidemiology of malaria Clinical picture Mode of transmission Risk factors Prevention and control Malaria is a life-threatening disease caused by Plasmodium parasites