Work Package 4: Developing new tools to target mosquitoes outside the home

IFIKARA HEALTH INSTITUTE UNIVERSITY OF GLASGOW

WP4 Team

 

Work Package Leader:  Dr Gerry Kileen. IHI

Objectives: 

Test a range of interventions to specifically target malaria transmission caused by mosquitoes biting outside the home

 

 

 

 

 

 

 

Tasks 

 Progress & plans 

 

Measure efficacy of insecticidal treatments for livestock

Having established the insecticides typically used by livestock owners to protect against ectoparasites, these were tested in experimental huts to see whether this mode of application could kill a sufficient number of mosquitoes to reduce the risk of malaria transmission in humans living in close proximity to cattle.  Significantly fewer live mosquitoes were collected in huts containing insecticide treated cattles than in controls.  The risk of diverting mosquitoes from cows to humans was found to be minimal at distances > 15m.

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Measure efficacy of transfluthrin

Spatial repellents can provide protection from mosquito bites but the strength of this protection and its duration have not been quantified. IHI scientists have found that sisal sacking, treated with the volatile pyrethroid, transfluthin, can provide long lasting protection to humans within 10 m of the source. However, exposure risk increased to those >40 m away.  This information is being used to optimise strategies to utilise this, and similar products, to reduce the risk of outdoor transmission of malaria, which is becoming an increasing concern in many parts of Africa.

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Measure efficacy of odour baited traps

Odour baited traps, strategically placed to capture mosquitoes as they emerge from their breeding sites and look for a human blood meal, could represent an important addition to malaria control toolbox.  In this task, various designs of odour baited traps were compared and significant improvements to the original prototype made.  Unfortunately trials of alternative sources of carbon dioxide found nothing that came close to results obtained with bottled carbon dioxide .  The need for bottle gas rendered the deployment of these traps at scale in practical and the task was terminated early.

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Publications & Outcomes

G.F. Killeen, N.J. Govella, D. W. Lwetoijera, F. O. Okumu. Most outdoor malaria transmission by behaviourally-resistant Anopheles arabiensis is mediated by mosquitoes that have previously been inside houses, where they may be readily targeted with improved indoor vector control methods. Malaria Journal 2016 15:225

N. J. Govella; S. B. Ogoma, J. Paliga, P. P. Chaki and G. F. Killeen. Impregnating hessian strips with the repellent pyrethroid transfluthrin prevents outdoor exposure to emerging pyrethroid resistant vectors of malaria and lymphatic filariasis in urban Dar es Salaam, Tanzania. Parasites & Vectors 2015, 8:322

G. F. Killeen and N. Chitnis. Potential causes and consequences of behavioural resilience and resistance in malaria vector populations: a mathematical modelling analysis. Malaria Journal 2014, 13:97

N. J. Govella; P. Chaki and G.F. Killeen. Entomological surveillance of behavioural resilience and resistance in residual malaria vector populations. Malaria Journal 2013 v12 (1) 124

G. F. Killeen; A. Seyoum; C. Sikaala; A. S. Zomboko; J. E. Gimnig; N. J. Govella and M. T. White. Eliminating Malaria Vectors. Parasites and Vectors. 2013.Vol 6, 172 

S. B. Ogoma;  H. Ngonyani; E. T. Simfukwe; A. Mseka; J. Moore and G. F. Killeen. Spatial repellency of transfluthrin-treated hessian strips against laboratory-reared Anopheles arabiensis. mosquitoes in a semi-field tunnel cage. BioMed Central. 2012. 5-54

N. J. Govella and H. M. Ferguson. Why use of interventions targeting outdoor biting mosquitoes will be necessary to achieve malaria elimination. Frontiers in Physiology 2014. Vol 3