advanced search

<< Back To Home

COMBINED USE OF SPRAYING AND LLINs

Thursday, 29th of December 2011

 ‘The combination of IRS and ITN might be a feasible strategy to further reduce malaria transmission in areas of persistent perennial malaria transmission.’ – Hamel et al.

‘The chlorfenapyr IRS component was largely responsible for controlling pyrethroid-resistant mosquitoes and the LLIN component was largely responsible for blood feeding inhibition and personal protection. Together, the combination shows potential to provide additional levels of transmission control and personal protection against pyrethroid-resistant mosquitoes, thereby justifying the additional resources required.’ – Ngufor et al.

• TWO ON COMBINED USE OF SPRAYING AND LLINs

Readers of the literature on malaria vector control have seen an uptick in publications on resistance. Will the combined use of residual spraying and LLINs slow the development of insecticide resistance?

1. 1.   Am J Trop Med Hyg 2011 vol. 85 no. 6 1080-1086   

• THE COMBINATION OF INDOOR RESIDUAL SPRAYING AND INSECTICIDE-TREATED NETS PROVIDES ADDED PROTECTION AGAINST MALARIA COMPARED WITH INSECTICIDE-TREATED NETS ALONE

1. 1.   Mary J. Hamel  et al.

↵*Address correspondence to Mary J. Hamel, Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30301. E-mail: mhamel@cdc.gov

Abstract.

Both insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS) reduce malaria in high malaria transmission areas.1–3 The combined effect of these interventions is unknown. We conducted a non-randomized prospective cohort study to determine protective efficacy of IRS with ITNs (ITN + IRS) compared with ITNs alone (ITN only) in preventing Plasmodium falciparum parasitemia. At baseline, participants provided blood samples for malaria smears, were presumptively treated for malaria, and received ITNs. Blood smears were made monthly and at sick visits. In total, 1,804 participants were enrolled. Incidence of P. falciparum parasitemia in the ITN + IRS and ITN only groups was 18 and 44 infections per 100 persons-years at risk, respectively (unadjusted rate ratio = 0.41; 95% confidence interval [CI] = 0.31–0.56). Adjusted protective efficacy of ITN + IRS compared with ITN only was 62% (95% CI = 0.50–0.72). The combination of IRS and ITN might be a feasible strategy to further reduce malaria transmission in areas of persistent perennial malaria transmission.

Disclaimer: Views expressed in this paper represent the authors and do not necessarily reflect the views of the US Centers for Disease Control and Prevention.

Accessible to AJTMH subscribers at http://www.ajtmh.org/content/85/6/1080.full.pdf+html

From Benin, see also http://www.malariajournal.com/content/10/1/343/abstract

• COMBINING INDOOR RESIDUAL SPRAYING WITH CHLORFENAPYR AND LONG-LASTING INSECTICIDAL BED NETS FOR IMPROVED CONTROL OF PYRETHROID-RESISTANT ANOPHELES GAMBIAE: AN EXPERIMENTAL HUT TRIAL IN BENIN

Corine Ngufor¹, Raphael N'Guessan^1,2, Pelagie Boko², Abibatou Odjo², Estelle Vigninou², Alex Asidi², Martin Akogbeto² and Mark Rowland^1*

• ·* Corresponding author: Mark Rowland mark.rowland@lshtm.ac.uk

Malaria Journal 2011, 10:343 doi:10.1186/1475-2875-10-343, published 16 November 2011

Abstract

Background

Neither indoor residual spraying (IRS) nor long-lasting insecticidal nets (LLINs) are able to fully interrupt transmission in holoendemic Africa as single interventions. The combining of IRS and LLINs presents an opportunity for improved control and management of pyrethroid resistance through the simultaneous presentation of unrelated insecticides.

Method

Chlorfenapyr IRS and a pyrethroid-impregnated polyester LLIN (WHO approved) were tested separately and together in experimental huts in southern Benin against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus. The bed nets were deliberately holed with either six or 80 holes to examine the effect of increasing wear and tear on protectiveness. Anopheles gambiae were genotyped for the kdr gene to assess the combination's potential to prevent the selection of pyrethroid resistance.

Results

The frequency of kdr was 84%. The overall mortality rates of An. gambiae were 37% and 49% with the six-hole and 80-hole LLINs, respectively, and reached 57% with chlorfenapyr IRS. Overall mortality rates were significantly higher with the combination treatments (82-83%) than with the LLIN or IRS individual treatments. Blood feeding (mosquito biting) rates were lowest with the 6-hole LLIN (12%), intermediate with the 80-hole LLIN (32%) and highest with untreated nets (56% with the 6-hole and 54% with the 80-hole nets). Blood feeding (biting) rates and repellency of mosquitoes with the combination of LLIN and chlorfenapyr IRS showed significant improvement compared to the IRS treatment but did not differ from the LLIN treatments indicating that the LLINs were the primary agents of personal protection. The combination killed significantly higher proportions of Cx. quinquefasciatus (51%, 41%) than the LLIN (15%, 13%) or IRS (32%) treatments.

Conclusion

The chlorfenapyr IRS component was largely responsible for controlling pyrethroid-resistant mosquitoes and the LLIN component was largely responsible for blood feeding inhibition and personal protection. Together, the combination shows potential to provide additional levels of transmission control and personal protection against pyrethroid-resistant mosquitoes, thereby justifying the additional resources required. Chlorfenapyr has potential to manage pyrethroid resistance in the context of an expanding LLIN/IRS strategy.

Related references:

1.        Lengeler C , 2004 . Insecticide-treated bed nets and curtains for preventing malaria . Cochrane Database Syst Rev 2: CD000363 .

2.       Pluess B , Tanser FC , Lengeler C , Sharp BL , 2010 . Indoor residual spraying for preventing malaria . Cochrane Database Syst Rev 4:CD006657 .

3.       Sharp BL , Ridl FC , Govender D , Kuklinski J , Kleinschmidt I , 2007 Malaria vector control by indoor residual insecticide spraying on the tropical island of Bioko, Equatorial Guinea . Malar J 6: 52

4.       Kleinschmidt I , Schwabe C , Benavente L , Torrez M , Ridl FC , Segura JL , Ehmer P , Nchama GN  2009 . Marked increase in child survival after four  years of intensive malaria control . Am J Trop Med Hyg 80: 882 – 888 .