Possible Interruption of Malaria Transmission | CDC EID

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Volume 15, Number 12–December 2009
Research
Possible Interruption of Malaria Transmission, Highland Kenya, 2007–2008
Chandy C. John, Melissa A. Riedesel, Ng'wena G. Magak, Kim A. Lindblade, David M. Menge, James S. Hodges, John M. Vulule, and Willis Akhwale
Author affiliations: University of Minnesota Medical School, Minneapolis, Minnesota, USA (C.C. John, M.A. Riedesel, D.M. Menge); Moi University School of Medicine, Eldoret, Kenya (N.G. Magak); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (K.A. Lindblade); University of Minnesota, Minneapolis (J.S. Hodges); Kenya Medical Research Institute, Kisian, Kenya (J.M. Vulule); and Ministry of Health, Nairobi, Kenya (W. Akhwale)

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Abstract
Highland areas where malaria transmission is unstable are targets for malaria elimination because transmission decreases to low levels during the dry season. In highland areas of Kipsamoite and Kapsisiywa, Kenya (population ≈7,400 persons), annual household indoor residual spraying with a synthetic pyrethroid was performed starting in 2005, and artemether/lumefantrine was implemented as first-line malaria treatment in October 2006. During April 2007–March 2008, no microscopy-confirmed cases of malaria occurred at the sites. In 4 assessments of asymptomatic persons during May 2007–April 2008, a total of <0.3% of persons were positive for asexual Plasmodium falciparum by microscopy or PCR at any time, and none were positive by PCR at the last 2 sample collections. Our findings show that in such areas, interruption and eventual elimination of malaria transmission may be achievable with widespread annual indoor residual spraying of households and artemisinin combination therapy.

Widespread implementation of malaria control interventions such as insecticide-treated bed nets (ITNs) and artemisinin combination therapy (ACT) have resulted in dramatic reductions of transmission in areas where this disease is endemic (1–3). For the first time since the 1950s, the World Health Organization and other organizations are promoting malaria eradication (4). In highland areas (>1,500 m above sea level) in Africa, malaria transmission is unstable, with a low incidence of malaria during dry seasons (5). These areas may be ideal initial targets for attempting the interruption of malaria transmission. Also in these areas, the combination of ACT, which may decrease transmission by reducing gametocyte load in infected persons, and annual indoor residual spraying (IRS) with long-lasting insecticides, which can reduce indoor vector density for a prolonged period, could act synergistically to interrupt malaria transmission.

We have conducted malaria epidemiology studies in the adjoining highland areas of Kipsamoite and Kapsisiywa, Nandi Hills District, Kenya, since 2003. Starting in 2005, the Ministry of Health of Kenya introduced new interventions to reduce malaria transmission and improve malaria treatment in these areas. Interventions introduced included IRS, distribution of ITNs to pregnant women and their children <5 years of age, and provision of artemether/lumefantrine (co-artemether) as first-line therapy for uncomplicated malaria. The present study documents the changes in malaria transmission that occurred during the period of these interventions and provides evidence that malaria transmission was interrupted during April 2007–March 2008.

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