Work Package Leader: Dr Caroline Jones. LSHTM
Experimental hut trials to explore alternative delivery systems for insecticides
This study took a multicentre approach carrying out two six weeks trials of the same interventions in three study sites. This approach was chosen to allow us to compare the efficacy of the single interventions and combined interventions against malaria vector populations with different levels of insecticide resistance. The sites selected were:
Muheza, Tanzania where vectors are susceptible to pyrethroid and organophosphates
Vallee du Kou, Burkina Faso, where local vectors are resistant to pyrethroid but susceptible to organophosphates and
Tiassale, Cote D’Ivoire where vectors are resistant to both pyrethroids and organophosphates.
This was then followed by combination trials in Burkina Faso and Cote d’Ivoire using:
P-methyl treated DL and NWH outperformed pyrethroid treated DL and NWH in all study sites demonstrating their potential efficacy against pyrethroid susceptible and resistant populations of malaria vectors.
P-methyl DL and NWH killed almost all pyrethroid resistant An gambiae that entered the experimental huts in Vallee du Kou since the population was largely susceptible to the OP. Even though this high kill was not observed in Tiassale owing to the presence of organophosphate resistance at this site, the p-methyl wall treatments still performed better than the pyrethroid. However, molecular studies show that these interventions when applied alone will likely select Ace 1R bearing mosquitoes leading to an increase in organophosphate resistance if deployed singly on a large scale.
P-methyl NWH were found to be easier to set up on walls compared to p-methyl DL. However in all three sites, the bioactivity of the insecticide on the treated materials declined to about 50% by the end of the six week trial. Thus alternative formulations of P-methyl are needed before P-methyl treated NWH or DL can be considered as an option for vector control.
Evaluation of larval source management (LSM) targeted in space and time
This activity involves two sites.
In Dar es Salaam, the original AvecNet objective was to evaluate larviciding targeted in space (to the most productive breeding sites) compared to blanket coverage. However, this coincided with the scale up of larviciding under the Dar es Salaam City Council Urban Malaria Control Programme (UMCP) and hence this study design was not possible. Instead AvecNet supported UMCP by providing detailed maps of the city and breeding sites and evaluating the impact of expanding the geographical distribution of larviciding on adult mosquito densities.
In Western Kenya the operational feasibility and efficiency of LSM strategies using Sumilarv 0.5G targeted in time during the long rainy season only (4 months: March to June) was investigated and found to have a similar impact on habitat colonisation throughout the year as all-year-round application. Emergence rates from time-targeted habitats were significantly reduced throughout the year even during the low transmission season indicating that the impact of the applications lasted several months beyond the last date of application. Even though reductions were not as high as those observed in the all-year round interventions, we consider them sufficiently high to warrant further exploration of this time-targeted strategy for integrated malaria vector control targeting the main transmission season as this strategy would involve just 6 application cycles per year, compared to the 52 applications per year used in current strategies.
Publications & Outcomes
Daniel Msellemu, Hagai I. Namango, Victoria M. Mwakalinga, Alex J. Ntamatungiro, Yeromin Mlacha, Zacharia J. Mtema, Samson Kiware, Neil F. Lobo, Silas Majambere, Stefan Dongus, Christopher J. Drakeley, Nicodem J. Govella, Prosper P. Chaki, and Gerry F. Killeen. The epidemiology of residual Plasmodium falciparum malaria transmission and infection burden in an African city with high coverage of multiple vector control measures. Malaria Journal 2016 15:288
Victoria M. Mwakalinga,Benn K. D. Sartorius, Yeromin P. Mlacha, Daniel F. Msellemu, Alex J. Limwagu, Zawadi D. Mageni, John M. Paliga, Nicodem J. Govella, Maureen Coetzee, Gerry F. Killeen and Stefan Dongus. Spatially aggregated clusters and scattered smaller loci of elevated malaria vector density and human infection prevalence in urban Dar es Salaam, Tanzania. Malaria Journal 2016 15:135
E.W. Kaindoa, G. Mkandawile, G. Ligamba, L. A. Kelly-Hope, F. O. Okumu. Correlations between household occupancy and malaria vector biting risk in rural Tanzanian villages: implications for high-resolution spatial targeting of control interventions. Malaria Journal 2016 15:199
B.A. Ndenga; N.L. Mulaya, S.K. Musaki, J.N. Shiroko, S.Dongus and U.Fillinger Malaria vectors and their blood‑meal
sources in an area of high bed net ownership in the western Kenya highlands. Malaria Journal 2016 15:76
C. Ngufor; M. Chouaïbou; E. Tchicaya; B. Loukou; N. Kesse; R. N’Guessan; P. C. D. Johnson; B. G. Koudou and M. Rowland. Combining organophosphate treated wall linings and long-lasting insecticidal nets fails to provide additional control over LLIN alone against multiple insecticide resistant Anopheles gambiae in Côte D’Ivoire: an experimental hut trial. Malaria Journal 2014, 13:396
C. Ngufor; P. Tungu; R. Malima; M. Kirby; W. Kisinza and M. Rowland. Insecticide-treated net wall hangings for malaria vector control: an experimental hut study in north-eastern Tanzania. Malaria Journal 2014, 13:366
C. N'gufor; E. Tchicaya; B. Koudou; S. N’Fale; R. Dabire; P. C. D. Johnson; H. Ranson and M. Rowland. Combining Organophosphate Treated Wall Linings and Long-lasting insecticidal Nets for improved control of Pyrethroid Resistant Anopheles gambiae. PlosOne 2014. Volume 9, Issue 1, e83897
P. P. Chaki; K. Kannady; D. Mtasiwa; M. Tanner; H. Mshinda; A. H. Kelly and G. F. Killeen. Institutional evolution of a community-based programme for malaria control through larval source management in Dar es Salaam, United Republic of Tanzania. Malaria Journal 2014, 13:245
Constant A.V. Edi, Luc Djogbénou, Adam M. Jenkins, Kimberly Regna, Marc A. T. Muskavitch, Rodolphe Poupardin, Christopher M. Jones, John Essandoh, Guillaume K. Kétoh, Mark J. I. Paine, Benjamin G. Koudou, Martin J. Donnelly, Hilary Ranson, David Weetman. CYP6 P450 Enzymes and ACE-1 Duplication Produce Extreme and Multiple Insecticide Resistance in the Malaria Mosquito Anopheles gambiae. PLOS Genetics, Vol 10, Issue 3, March 2014
H. Ranson. Facing the resistance crisis in malaria control by developing and evaluating ‘resistance-breaking’ products. Outlooks in Pest Management. February 2014. p.33
O. Mbare, S. W. Lindsay, U. Filinger. Dose–response tests and semi-field evaluation of lethal and sub-lethal effects of slow release pyriproxyfen granules (Sumilarv®0.5G) for the control of the malaria vectorsAnopheles gambiae sensu lato. Malaria Journal 2013 12:94