Background: In Morocco, the main strategies of leishmaniasis vector control are based on environmental modifications. Use of local residual indoor spraying with synthetic pyrethroids is often envisaged. The need to evaluate this control method is essential. The current study was conducted to determine the efficacy of an alphacypermethrin IRS program against leishmaniasis vectors in an endemic area in the north of Morocco.
Methods: The survey was conducted in four neighbouring localities in three different districts in northern Morocco: Ait Chaib and Aichoun in Sefrou district, Bouassem (Boulmane) and Lmrouj (Taounate). Indoor residual spraying with alphacypermethrin at a dose of 30 mg/m2 was used in Ait Chaib and Lmrouj localities during 2010, 2011 and 2012, while localities of Aichoun and Bouassem were taken as control. In the four studied areas, sand flies were collected bimonthly from April to November in 2011 and 2012, using sticky traps, to determine their abundance and feeding pattern. Alphacypermethrin IRS were evaluated for their residual effect using the WHO cone bioassay test. Leishmaniasis incidence was estimated by passive and active case detection in each study area.
Results: Significant reductions in leishmaniasis incidence and in gravidity rate were observed when comparing sprayed and unsprayed localities. The residual activity of alphacypermethrin at the concentration used lasted 10 weeks after spraying. However, the abundance of sand flies was not significantly affected by alphacypermethrin IRS.
Conclusion: This study indicated that IRS has a significant impact on leishmaniasis transmission; therefore it could be recommended as an effective tool for leishmaniasis control in areas with high leishmaniasis transmission.