Abilio et al. Malaria Journal 2011, 10:110 http://www.malariajournal.com/content/10/1/110 RESEARCH Open Access The emergence of insecticide resistance in central Mozambique and potential threat to the successful indoor residual spraying malaria control programme Ana P Abilio1, Immo Kleinschmidt2, Andrea M Rehman2, Nelson Cuamba1, Varsha Ramdeen3, David S Mthembu3, Sarel Coetzer3, Rajendra Maharaj3, Craig S Wilding4, Andrew Steven4, Marlize Coleman4, Janet Hemingway4 and Michael Coleman4* Abstract Background: Malaria vector control by indoor residual spraying was reinitiated in 2006 with DDT in Zambézia province, Mozambique. In 2007, these efforts were strengthened by the President’s Malaria Initiative. This manuscript reports on the monitoring and evaluation of this programme as carried out by the Malaria Decision Support Project. Methods: Mosquitoes were captured daily through a series of 114 window exit traps located at 19 sentinel sites, identified to species and analysed for sporozoites. Anopheles mosquitoes were collected resting indoors and tested for insecticide resistance following the standard WHO protocol. Annual cross sectional household parasite surveys were carried out to monitor the impact of the control programme on prevalence of Plasmodium falciparum in children aged 1 to 15 years. Results: A total of 3,769 and 2,853 Anopheles gambiae s.l. and Anopheles funestus, respectively, were captured from window exit traps throughout the period. In 2010 resistance to the pyrethroids lambda-cyhalothrin and permethrin and the carbamate, bendiocarb was detected in An. funestus. In 2006, the sporozoite rate in An. gambiae s.s. was 4% and this reduced to 1% over 4 rounds of spraying. The sporozoite rate for An. funestus was also reduced from 2% to 0 by 2008. Of the 437 Anopheles arabiensis identified, none were infectious. Overall prevalence of P. falciparum in the sentinel sites fell from 60% to 32% between October 2006 and October 2008. Conclusion: Both An. gambiae s.s. and An. funestus were controlled effectively with the DDT-based IRS programme in Zambézia, reducing disease transmission and burden. However, the discovery of pyrethroid resistance in the province and Mozambique’s policy change away from DDT to pyrethroids for IRS threatens the gains made here. Background To successfully control malaria, programmes must use The Roll Back Malaria, United Nations Millennium current tools efficiently. In moderate to high transmis- Development Goals and World Health Assembly univer- sion areas this requires the combination of effective vec- sal access and coverage targets for malaria prevention tor interventions, either indoor residual spraying of and treatment have been established to reduce disease insecticides (IRS) and/or insecticide-treated nets (ITNs), transmission. To meet these targets malaria control with effective drug treatment. To achieve this, continu- interventions are now being scaled up [1,2]. ous surveillance, monitoring and evaluation (M & E) need to be integrated into the malaria control pro- gramme. There are very few examples of good malaria M * Correspondence: [email protected] 4Liverpool School of Tropical Medicine, Pembroke Place, Liverpool. L3 5QA, & E, which include parasitological, disease transmission UK and entomological data assessment. These include Bioko Full list of author information is available at the end of the article © 2011 Abilio et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abilio et al. Malaria Journal 2011, 10:110 Page 2 of 9 http://www.malariajournal.com/content/10/1/110 island [3,4], the cross border Lubombo Spatial Develop- out in Oct/Nov 2006 and subsequently each year in all ment Initiative (LSDI) [5], Eritrea [6] and Zambia [7]. districts except for Maganja da Costa, where LLINs (both In Mozambique, the National Malaria Control Pro- Olyset, Sumitomo Chemical and Permanent, Vestergaard gramme (NMCP) used DDT for IRS before a change in Frandsen) were distributed from 2009 (Figure 1). Ento- policy in 1993, when the pyrethroid lambda-cyhalothrin mological surveillance and cross-sectional malaria indica- was introduced in the southern part of the country. With tor surveys were carried out at all 19 sites. the discovery of Anopheles funestus resistant to pyre- throids in South Africa [8], the LSDI implemented an Insecticide resistance testing insecticide resistance monitoring programme in southern Indoor resting blood fed adult female Anopheles gam- Mozambique that showed in 1999 that both An. funestus biae s.l and An. funestus for insecticide resistance bioas- and Anopheles arabiensis were resistant to pyrethroids says were collected between hours 06.00-10.00 in houses [9,10] due to elevated p450s [11]. This resulted in an using an aspirator during the period Oct 2006 to May informed insecticide policy change to the carbamate 2010. Until 2009, wild caught mosquitoes were used for bendiocarb for IRS [5]. Bendiocarb was sprayed bi- insecticide susceptibility assays following the WHO annually in southern Mozambique until 2005, when, due insecticide susceptibility test protocol (WHO 1998). to the high economic costs associated with this insecti- Assays carried out on wild-caught mosquitoes did not cide, an operational change was made back to DDT. No allow for standardisation in age, physiological state or resistance has yet been detected to DDT in Mozambique. pre-exposure to insecticides. After the establishment of In 2005 the U.S. Government initiated the President’s an insectary in 2009, wild-caught female mosquitoes Malaria Initiative (PMI) [12], which supported the rapid were transported to the laboratory, kept in individual scale-up of malaria prevention and treatment in 15 coun- oviposition tubes with access to 10% sucrose and tries in Africa, including Mozambique. In central allowed to lay eggs. Each family was reared separately Mozambique, an IRS programme was initiated in six dis- through to 1-3 day old F1 adults at 26°C +/- 2°C and tricts in Zambézia province. Previously, the NMCP had 70-80% relative humidity allowing standardisation of age carried out vector control with sporadic IRS and fogging physiological state and testing conditions. Families were between 1995 and 2003 in this area. In 2005, the NMCP mixed prior to testing to avoid bias from isofemale lines resumed IRS in Zambézia in three districts, using DDT. where offspring may all be genetically similar. Between Limited expansion of activities occurred in 2006 to cover five and 25 adult mosquitoes were exposed to insecti- 5 districts and this effort was strengthened in 2007 by cide treated or control papers, impregnated with the PMI. The IRS was focused on densely populated areas carrier oil alone, for 1 hour and then transferred to using DDT or lambda-cyhalothrin, the latter being holding tubes with access to 10% sugar solution for 24 applied on structures not suitable for DDT (i.e. finished hours before the percentage mortality was determined. or painted walls). In 2009, pyrethroids were the sole class The insecticides tested were, deltamethrin (0.05%), of insecticides purchased for IRS, although all remaining lambda-cyhalothrin (0.05%), bendiocarb (0.01%), and stocks of DDT were sprayed during that year [13]. DDT (4%). All papers were supplied by WHO. Zambézia province was used to pilot and refine a new Malaria Decision Support System (MDSS) [14], which Species abundance and sporozoite rates was implemented in 19 sentinel sites in Zambézia pro- Prior to the initiation of IRS in 2006 a window exit trap vince in 2006 and served to evaluate and monitor the was installed in six houses at each sentinel site with the interventions described above. The objective of this home-owner’s permission. Home-owners were trained work was to determine whether the system, which was to empty the traps daily into pre-labelled specimen jars continuously improved during the course of the study, containing isopropanol and complete checklists indicat- could be deployed in a resource poor setting, with low ing the nights for which the traps were checked. level infrastructure and limited human capacity. The uti- lity to control programme managers of an integrated Species identification surveillance system providing real time monitoring Wild-caught females were morphologically identified as through a number of performance and impact indica- belonging to the An. gambiae s.l. complex or An. funes- tors, was clearly demonstrated. tus s.l. group [15,16]. Species identification within each complex was carried out by DNA-polymerase chain Methods reaction on a sample of specimens [17,18]. Study site and insecticide usage In 2006, 19 sentinel sites were established in six districts Sporozoite identification in Zambézia province, Mozambique. IRS with DDT (Hin- DNA was extracted from the head and thorax of a sub- dustan Insecticide limited, New Delhi, India) was carried sample of mosquitoes using the Livak method [19] and Abilio et al. Malaria Journal 2011, 10:110 Page 3 of 9 http://www.malariajournal.com/content/10/1/110 Figure 1 Map showing the location of sentinel sites in Zambézia province, Mozambique. infection with Plasmodium species was determined sentinel site were estimated taking account of clustering using a multiplex real time PCR [20]. by sentinel site using the statistical