title: The epidemiology of residual Plasmodium falciparum malaria transmission and infection burden in an African city with high coverage of multiple vector control measures.
abstract: In the Tanzanian city of Dar es Salaam, high coverage of long-lasting insecticidal nets (LLINs), larvicide application (LA) and mosquito-proofed housing, was complemented with improved access to artemisinin-based combination therapy and rapid diagnostic tests by the end of 2012.
  
  
  
  Three rounds of city-wide, cluster-sampled cross-sectional surveys of malaria parasite infection status, spanning 2010 to 2012, were complemented by two series of high-resolution, longitudinal surveys of vector density.
  
  
  
  Larvicide application using a granule formulation of Bacillus thuringiensis var. israelensis (Bti) had no effect upon either vector density (P = 0.820) or infection prevalence (P = 0.325) when managed by a private-sector contractor. Infection prevalence rebounded back to 13.8 % in 2010, compared with <2 % at the end of a previous Bti LA evaluation in 2008. Following transition to management by the Ministry of Health and Social Welfare (MoHSW), LA consistently reduced vector densities, first using the same Bti granule in early 2011 [odds ratio (OR) (95 % confidence interval (CI)) = 0.31 (0.14, 0.71), P = 0.0053] and then a pre-diluted aqueous suspension formulation from mid 2011 onwards [OR (95 % CI) = 0.15 (0.07, 0.30), P ≪ 0.000001]. While LA by MoHSW with the granule formulation was associated with reduced infection prevalence [OR (95 % CI) = 0.26 (0.12, 0.56), P = 0.00040], subsequent liquid suspension use, following a mass distribution to achieve universal coverage of LLINs that reduced vector density [OR (95 % CI) = 0.72 (0.51, 1.01), P = 0.057] and prevalence [OR (95 % CI) = 0.80 (0.69, 0.91), P = 0.0013], was not associated with further prevalence reduction (P = 0.836). Sleeping inside houses with complete window screens only reduced infection risk [OR (95 % CI) = 0.71 (0.62, 0.82), P = 0.0000036] if the evenings and mornings were also spent indoors. Furthermore, infection risk was only associated with local vector density [OR (95 % CI) = 6.99 (1.12, 43.7) at one vector mosquito per trap per night, P = 0.037] among the minority (14 %) of households lacking screening. Despite attenuation of malaria transmission and immunity, 88 % of infected residents experienced no recent fever, only 0.4 % of these afebrile cases had been treated for malaria, and prevalence remained high (9.9 %) at the end of the study.
  
  
  
  While existing vector control interventions have dramatically attenuated malaria transmission in Dar es Salaam, further scale-up and additional measures to protect against mosquito bites outdoors are desirable. Accelerated elimination of chronic human infections persisting at high prevalence will require active, population-wide campaigns with curative drugs.
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Msellemu
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|School of Biological Sciences, University of Nairobi, Nairobi, Kenya.
authors.forename: Hagai I
authors.initials: HI
authors.lastname: Namango
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Mwakalinga
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Ntamatungiro
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
authors.forename: Yeromin
authors.initials: Y
authors.lastname: Mlacha
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.
authors.forename: Zacharia J
authors.initials: ZJ
authors.lastname: Mtema
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, USA.
authors.forename: Samson
authors.initials: S
authors.lastname: Kiware
authors.affiliation: Eck Institute for Global Health, Notre Dame University, Notre Dame, IN, USA.
authors.forename: Neil F
authors.initials: NF
authors.lastname: Lobo
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
authors.forename: Silas
authors.initials: S
authors.lastname: Majambere
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.|Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Dongus
authors.affiliation: Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Drakeley
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
authors.forename: Nicodem J
authors.initials: NJ
authors.lastname: Govella
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
authors.forename: Prosper P
authors.initials: PP
authors.lastname: Chaki
authors.affiliation: Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania. gkilleen@ihi.or.tz.|Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK. gkilleen@ihi.or.tz.
authors.forename: Gerry F
authors.initials: GF
authors.lastname: Killeen
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000453:epidemiology; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000517:prevention & control* / Q000635:transmission; D008297:Male; D008875:Middle Aged; D009032:Mosquito Control / Q000379:methods*; D015995:Prevalence; D013636:Tanzania / Q000453:epidemiology; D055815:Young Adult
keywords: Anopheles; Chronic infection; Housing; Larval source management; Long-lasting insecticidal net; Malaria; Mosquito; Plasmodium; Vector control; Window screening