MALARIA VECTOR SUSCEPTIBILITY IN RWANDA. 1ST RWANDA MALARIA FORUM RESULTS By Emmanuel Hakizimana September 27 th, 2012

INTRODUCTION Rwanda is strongly committed towards malaria control with the ultimate goal of eliminating this disease. Vector control using insecticides is one of the key components of malaria control strategies A significant reduction of morbidity and mortality is achieved when the efficacy of vector control interventions is continuously maintained at a high level The selection of insecticides for use in IRS and LLINs is highly dependent on the extent to which local mosquitoes are susceptible to the approved classes of insecticides.

Background and Rationale (Cont.) Documented cases of resistance or development of resistance in mosquito populations associated with: – Agriculture (Brogdon et al. 1988b; Chouaibou et al. 2008) – IRS (Brogdon et al. 1988a; Lines, 1988) – ITNs (Vulule et al. 1999; Corbel et al. 2004; Rubaihayo et al. 2008) – Use of household insecticides (sprays, coils etc.) (Akogbeto & Yakoubou, 1999) Since 2009, insecticide resistance monitoring is one of the package of entomology surveillance in sentinel sites with a frequence of once a year.

Objectives To evaluate the susceptibility of malaria vectors to the main insecticides recommended by WHO and used in country ( Deltamethrin, Permethrin, Lambdacyhalothrin, DDT, Fernitrothion, Bendiocarb ) in differents ecosytems of Rwanda. Enlighten scientific recommendation of insecticides for interventions of malaria vector control in Rwanda

Study sites: 14 sites countrywide

Methods – Test procedures CDC bottles (in 2010) and WHO standards protocol, 1998 (since 2011) Non-blood fed females of Anopheles gambiae s.l. aged 2-3 days old of the local strains from larvae collected from field and reared in field insectary Knockdown and mortality rates were recorded at 10, 15, 20, 30, 40, 50, 60 min and 24h post exposure respectively

RESULTS WITH CDC BOTTLES,

Susceptible tests conducted on An. gambiae s.l. in 8 sites with CDC bottle,

RESULTS WITH WHO STANDARD PROTOCOL (1998) 9

Time of Knockdown for 6 insecticides tested

Time for 50% knockdown (KDT50) by Deltamethrin 0.05% (Py)

Time for 50% knockdown (KDT50) by Permethrin 0.75% (Pyrethroid)

Time for 50% knockdown (KDT50) by Lambdacyhalothrin 0.75% (Py)

Time for 50% knockdown (KDT50) by DDT 4.0 % (Organochlorines)

Time for 50% knockdown (KDT50) by Bendiocarb 0.1% (Carbamates)

Time for 50% knockdown (KDT50) by Fenitrothion 1.0% (Organophosphates)

Mortality after 24 hrs of exposure

Interpretation of Results >98% mortality= susceptible 100 mosquitoes= strong suspicion of resistance % mortality= resistance suspected; < 80% mortality= resistant individuals present

National average mortality obtained for six Insecticides

Susceptibility status of A. gambiae s.l. to Pyrethroids (commonly used for vector control) 20

Susceptibility status of A. gambiae s.l. to to other classes of insecticide 21

PCR – Identification & kdr gene (Partial Results)

PCR-Identification,

PCR-Identification, 2011

PCR-kdr gene, 2008

PCR-kdr gene, 2011

Conclusion Until 2011, malaria vectors were more sensitive to lambdacyhalothrin (Pyrethroids) and to Fenitrothion (Organophosphates) More suspicious of resistance to Pyrethroids. High prevalence of gene KDR which would explain the suspicion of resistance to Pyrethroids Insecticide resistance has been confirmed in 3 sites with DDT 4% Occurrence of Anopheles arabiensis as predominant of malaria vectors since 2011 in almost study sites. Continue susceptibility tests and dynamic of malaria vector species