The epidemiology of residual Plasmodium falciparum malaria transmission and infection burden in an African city with high coverage of multiple vector control measures

Malaria Journal

Research

Christopher J. Drakeley¹  Neil F. Lobo²  Zacharia J. Mtema³  Daniel Msellemu⁴  Alex J. Ntamatungiro⁴  Samson Kiware⁵  Gerry F. Killeen⁶  Silas Majambere⁶  Yeromin Mlacha⁶  Prosper P. Chaki⁶  Nicodem J. Govella⁶  Stefan Dongus⁷  Hagai I. Namango⁸  Victoria M. Mwakalinga⁹ 

[1] Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK;Eck Institute for Global Health, Notre Dame University, Notre Dame, IN, USA;Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania;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;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;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;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;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;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;

关键词: Malaria;    Plasmodium;    Mosquito;    Anopheles;    Vector control;    Larval source management;    Housing;    Window screening;    Chronic infection;    Long-lasting insecticidal net;   

DOI  :  10.1186/s12936-016-1340-4

 received in 2016-01-31, accepted in 2016-05-11,  发布年份 2016

来源: Springer

【 摘 要 】

BackgroundIn 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.MethodsThree 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.ResultsLarvicide 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.ConclusionsWhile 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.

【 授权许可】

CC BY   
© The Author(s). 2016