Home > Global > Urban malaria annotated bibliography, Jan 2008-Feb 2009

Urban malaria annotated bibliography, Jan 2008-Feb 2009

This bibliography contains citations and abstracts to 16 urban malaria studies published from January 2008 through February 2009. Links to author email addresses and full-text are included when available.

1: Acta Trop. 2008 Jan;105(1):81-6.

Marked differences in the prevalence of chloroquine resistance between urban and rural communities in Burkina Faso.

Meissner PE, Mandi G, Mockenhaupt FP, Witte S, Coulibaly B, Mansmann U, Frey C, Merkle H, Burhenne J, Walter-Sack I, Müller O.

Department of Tropical Hygiene and Public Health, Ruprecht-Karls-University, Heidelberg, Germany. peter.meissner@urz.uni-heidelberg.de

BACKGROUND: Chloroquine (CQ) resistance has reached high levels in Africa in recent years. Little is known about variations of resistance between urban and rural areas. OBJECTIVES: To compare the rates of in vivo resistance to CQ and the prevalences of the main molecular marker for CQ resistance among young children
from urban and rural areas in Burkina Faso. METHODS: The current analysis used the frame of a randomized controlled trial (ISRCTN27290841) on the combination CQ-methylene blue (MB) (n=177) compared to CQ alone (n=45) in young children with uncomplicated malaria. We examined clinical and parasitological failure rates as well as the prevalence of the Plasmodium falciparum chloroquine resistance transporter gene (pfcrt) T76 mutation. RESULTS: Clinical and parasitological failure rates of CQ-MB differed significantly between urban (70%) and rural areas (29%, p<0.0001). Likewise, CQ failure rates were higher in the urban setting. Matching this pattern, pfcrt T76 was more frequently seen among parasite strains from urban areas (81%) when compared to rural ones (64%, p=0.01). In the presence of parasites exhibiting pfcrt T76, the odds of overall clinical failure were increased to 2.6-fold ([1.33, 5.16], p(LR)=0.005). CQ was detected at baseline in 21% and 2% of children from the urban and the rural study area, respectively (p(Chi)=0.002). CONCLUSION: Even within circumscribed geographical areas, CQ efficacy can vary dramatically. The differences in the prevalence of pfcrt T76 and in CQ failure rates are probably explained by a higher drug pressure in the urban area compared to the rural study area. This finding has important implications for national malaria policies.

2: Am J Trop Med Hyg. 2009 Mar;80(3):487-91.

How much malaria occurs in urban Luanda, Angola? A health facility-based assessment.

Thwing JI, Mihigo J, Fernandes AP, Saute F, Ferreira C, Fortes F, de Oliveira AM, Newman RD.

Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.

We conducted a health facility-based survey of patients with fever during malaria transmission season to determine the proportion with laboratory-confirmed malaria in Luanda, Angola. We enrolled 864 patients at 30 facilities; each underwent a blood film for malaria and a questionnaire. Only 3.6% had a positive blood film. When stratified by distance of the facility to city center ( or = 15 km), the proportions were 1.5% (9/615) and 8.8% (22/249), respectively (P < 0.0001). Of patients traveling outside Luanda in the preceding 3 months, 6.8% (6/88) had malaria, compared with 3.2% (26/776) not traveling (P = 0.13). Children < 5 years of age were less likely to have malaria (2.4%; 12/510) than children ages 5-14 (8.7%; 9/104) and adults (4.0%; 10/250) (P = 0.03). The prevalence of laboratory-confirmed malaria in febrile patients in Luanda is very low, but increases with distance from the urban center. Prevention and treatment should be focused in surrounding rural areas.

3: Bull Soc Pathol Exot. 2008 Apr;101(2):124-7.

Self-medication in the treatment of acute malaria: study based on users of private health drug stores in Ouagadougou, Burkina Faso.

Ouédraogo LT, Somé IT, Diarra M, Guissou IP.

Département de santé publique, UFR/SDS, Université de Ouagadougou, BP 5705 Ouagadougou 01, Burkina Faso. laurent_tikar@yahoo.fr

In order to contribute to the national debate on the change of protocol of the simple forms of malaria treatment in Burkina Faso, we conducted a transversal descriptive study among 397 private pharmacies users in Ouagadougou. The aims of the study were: – making an inventory of the antimalarials and signs which led to self-medication; – identifying the factors favouring self-treatment and the reasons why these antimalarials have been bought; – making an inventory of the misuses of antimalarial drugs by individuals practicing self-medication; – checking the knowledge base in individuals practicing self-medication in relation to resistance to antimalarials. We noticed that chloroquine (39.3%), sulfadoxine-pyrimethamin (24.4%), arthemisinin and its by products (15.1%) were the three main molecules which account for antimalarial self-treatment However the use of these molecules was inappropriate regarding the dosage (41.3%) as well as the rate of intake (40.7%). Self-medication was motivated by the common signs of malaria and the way in which this parasitosis has become an every day feature in people’s minds. The choice of the molecule, the knowledge of the directions for use and the rate of intake were significantly linked to the level of education (p < 0.001). Self-medication being one of the major causes of resistance development, it is necessary together with local pharmacies retailers, to organize information campaigns on the correct use of molecules of the new antimalarial therapeutic scheme which will be adopted.

4: East Mediterr Health J. 2008 Jan-Feb;14(1):206-15.

Malaria control in an urban area: a success story from Khartoum, 1995-2004.

Elkhalifa SM, Mustafan IO, Wais M, Malik EM.

State Malaria Control Programme, Khartoum State, Khartoum, Sudan.

Khartoum is an urban area with low malaria transmission. Early control efforts were successful in reducing the risk but malaria has resurged in recent years. In 2002, the Government of Sudan, with support of the World Health Organization, embarked on an initiative aimed at freeing Khartoum of malaria. The initiative’s prevention strategy has focused on larval control interventions. The results indicate a significant reduction in malaria prevalence, confirmed and clinically diagnosed malaria cases among outpatient attendance and the number of malaria-associated deaths. It is proposed information be collected on parity rates and that a sub-sample of the adult mosquito collections be subjected to ELISA or PCR for identification of malaria parasite infections in mosquitoes in areas showing active foci.

5: Ecotoxicol Environ Saf. 2008 May;70(1):147-53.

Heavy metals in mosquito larval habitats in urban Kisumu and Malindi, Kenya, and their impact.

Mireji PO, Keating J, Hassanali A, Mbogo CM, Nyambaka H, Kahindi S, Beier JC.

Department of Biochemistry, Kenyatta University, P.O. Box 43844, Nairobi 00100, Kenya.

Concentrations and distribution of cadmium, chromium, copper, iron, lead, manganese and zinc in mosquito larval habitats in urban Kisumu and Malindi, Kenya and their effect on the presence of Anopheles gambiae, Aedes aegypti, Culex quinquefasciatus and Anopheles funestus larvae were investigated. Manganese and iron were the most prevalent heavy metals in water of larval habitats in urbanKisumu and Malindi, respectively. Iron was the most prevalent heavy metal in bottom sediments in larval habitats in both cities. The highest concentrations of all heavy metals, except cadmium and iron, were recorded in the poorly planned-well drained stratum in the two cities. All heavy metals were more concentrated in human-made than in natural larval habitats. Copper was positively associated with the presence of Ae. aegypti, and lead was associated with the presence of An. gambiae and Ae. aegypti in urban Kisumu. Absence of significant correlation between the other metals and mosquito species in both cities, despite relatively high concentrations, suggest that the local larval populations, including key malaria vectors have adapted to the detected levels of these metals.

6: Int J Hyg Environ Health. 2008 Oct;211(5-6):591-605.

Lead poisoning associated with malaria in children of urban areas of Nigeria.

Nriagu J, Afeiche M, Linder A, Arowolo T, Ana G, Sridhar MK, Oloruntoba EO, Obi E, Ebenebe JC, Orisakwe OE, Adesina A.

Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA. jnriagu@umich.edu

The principal objectives of this study are to (a) investigate the prevalence of elevated blood lead levels (EBLLs) in children of three major cities of Nigeria with different levels of industrial pollution; (b) identify the environmental, social and behavioral risk factors for the EBLLs in the children; and (c) explore the association between malaria (endemic in the study areas) and EBLLs in the pediatric population. The study involved 653 children aged 2-9 years (average, 3.7 years). The mean blood lead level (BLL) for the children was 8.9+/-4.8microg/dL, the median value was 7.8microg/dL, and the range was 1-52microg/dL. About 25% of the children had BLL greater than 10microg/dL. There were important differences in BLLs across the three cities, with the average value in Ibadan (9.9+/-5.2microg/dL) and Nnewi (8.3+/-3.5microg/dL) being higher than that in Port Harcourt (4.7+/-2.2micro/dL). Significant positive associations were found between BLL and a child’s town of residence (p<0.001), age of the child (p=0.004), length of time the child played outside (p<0.001), presence of pets in a child’s home (p=0.023), but negatively with educational level of caregiver (p<0.001). This study is one of the first to find a significant negative association between BLL and malaria in a pediatric population, and this association remained significant after controlling for confounding diseases and symptoms. The shared environmental and socio-demographic risks factors for lead exposure and Plasmodium (most common malaria parasites) infection in urban areas of Nigeria are discussed along with possible ways that lead exposure may influence the host response to infection with malarial parasites.

7: J Am Mosq Control Assoc. 2008 Sep;24(3):410-4.

Field evaluation of a previously untested strain of biolarvicide (Bacillus thuringiensis israelensis H14) for mosquito control in an urban area of Orissa, India.

Sharma SK, Upadhyay AK, Haque MA, Raghavendra K, Dash AP. National Institute of Malaria Research, Field Station, Sector-5, Rourkela-769 002, Orissa, India.

A previously untested strain of Bacillus thuringiensis israelensis (Bti) serotype H14 (ID No. VCRC B17) has been evaluated under field conditions in an urban area of Rourkela city, India for its impact on the larval density of different mosquito species in a variety of habitats. The persistence of the biolarvicide used in an aqueous solution varied in different habitats. The lowest field application rate of 0.5 ml/m2 remained effective for about 10-12 days and provided 80-100% reduction in larval abundance of anopheline species, including Anopheles culicifacies breeding in unpolluted water bodies. However, in stagnant polluted waters in drains and cesspools supporting culicine breeding, the biocide at the same rate persists for 5-6 days only. An application rate of 1 ml/m2 to stagnant drains and cesspools, resulted in 84-100% reduction in the larval population of Culex quinquefasciatus over a period of 2 wk. Based on the field observations, an operational dose of 0.5 ml/m2 at fortnightly intervals is suggested for clean water sources supporting anopheline breeding. However, to control breeding of culicine mosquitoes in stagnant and polluted waters, an operational dose of 1 ml/m2 at fortnightly intervals is required. The study showed that Bti serotype H14 (VCRC B17) is a suitable biolarvicide that can be used against different mosquitoes in different types of urban habitats.

8: J Infect Dis. 2008 Sep 15;198(6):920-7.

Plasmodium falciparum and helminth coinfection in a semi urban population of pregnant women in Uganda.

Hillier SD, Booth M, Muhangi L, Nkurunziza P, Khihembo M, Kakande M, Sewankambo M, Kizindo R, Kizza M, Muwanga M, Elliott AM.

The University of Birmingham Medical School, Birmingham, United Kingdom. sdhillier@doctors.org.uk

BACKGROUND: Helminth infections and malaria are widespread in the tropics. Recent studies suggest helminth infections may increase susceptibility to Plasmodium falciparum infection. If confirmed, this increased susceptibility could be particularly important during pregnancy-induced immunosuppression. OBJECTIVE: To evaluate the geographical distribution of P. falciparum-helminth coinfection and the associations between P. falciparum infection and infection with various parasite species in pregnant women in Entebbe, Uganda. METHODS: A cross-sectional study was conducted at baseline during a trial of antihelminthic drugs during pregnancy. Helminth and P. falciparum infections were quantified in 2,507 asymptomatic women. Subjects’ socioeconomic and demographic characteristics and geographical details were recorded. RESULTS: Hookworm and Mansonella perstans infections were associated with P. falciparum infection, but the effect of hookworm infection was seen only in the absence of M. perstans infection. The odds ratio [OR] for P. falciparum infection, adjusted for age, tribe, socioeconomic status, HIV infection status, and location was as follows: for individuals infected with hookworm but not M. perstans, 1.53 (95% confidence interval [CI], 1.09-2.14); for individuals infected with M. perstans but not hookworm, 2.33 (95% CI, 1.47-3.69); for individuals infected with both hookworm and M. perstans, 1.85 (CI, 1.24-2.76). No association was observed between infection with Schistosoma mansoni, Trichuris, or Strongyloides species and P. falciparum infection. CONCLUSIONS: Hookworm-P. falciparum coinfection and M. perstans-P. falciparum coinfection among pregnant women in Entebbe is more common than would be expected by chance. Further studies are needed to elucidate the mechanism of this association. A helminth-induced increase in susceptibility to P. falciparum could have important consequences for pregnancy outcome and
responses to P. falciparum infection in infancy.

9: Malar J. 2009 Jan 13;8:13.

Social and environmental malaria risk factors in urban areas of Ouagadougou, Burkina Faso.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-8-13.pdf

Baragatti M, Fournet F, Henry MC, Assi S, Ouedraogo H, Rogier C, Salem G.

Parasite Biology and Epidemiology Research Dept, UMR- URMITE, IMTSSA, Parc du Pharo, Marseille-Armées, France. baragattimeili@hotmail.com

BACKGROUND: Despite low endemicity, malaria remains a major health problem in urban areas where a high proportion of fevers are presumptively treated using anti-malarial drugs. Low acquired malaria immunity, behaviour of city-dwellers, access to health care and preventive interventions, and heterogenic suitability of urban ecosystems for malaria transmission contribute to the complexity of the malaria epidemiology in urban areas. METHODS: The study was designed to identify the determinants of malaria transmission estimated by the prevalence of anti-circumsporozoite (CSP) antibodies, the prevalence and density of Plasmodium falciparum infection, and the prevalence of malarial disease in areas of Ouagadougou, Burkina-Faso. Thick blood smears, dried blood spots and clinical status have been collected from 3,354 randomly chosen children aged 6 months to 12 years using two cross-sectional surveys (during the dry and rainy seasons) in eight areas from four ecological strata defined according to building density and land tenure (regular versus irregular). Demographic characteristics, socio-economic information, and sanitary and environmental data concerning the children or their households were simultaneously collected. Dependent variables were analysed using mixed multivariable models with random effects, taking into account the clustering of participants within compounds and areas. RESULTS: Overall prevalences of CSP-antibodies and P. falciparum infections were 7.7% and 16.6% during the dry season, and 12.4% and 26.1% during the rainy season, respectively, with significant differences according to ecological strata. Malaria risk was significantly higher among children who i) lived in households with lower economic or education levels, iii) near the hydrographic network, iv) in sparsely built-up areas, v) in irregularly built areas, vi) who did not use a bed net, vii) were sampled during the rainy season or ii) had traveled outside of Ouagadougou. CONCLUSION: Malaria control should be focused in areas which are irregularly or sparsely built-up or near the hydrographic network. Furthermore, urban children would benefit from preventive interventions (e.g. anti-vectorial devices or chemoprophylaxis) aimed at reducing malaria risk during and after travel in rural areas.

10: Malar J. 2009 Jan 5;8:2.

Pattern of drug utilization for treatment of uncomplicated malaria in urban Ghana following national treatment policy change to artemisinin-combination therapy.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-8-2.pdf

Dodoo AN, Fogg C, Asiimwe A, Nartey ET, Kodua A, Tenkorang O, Ofori-Adjei D.

Centre for Tropical Clinical Pharmacology & Therapeutics, University of Ghana Medical School, P,O, Box KB 4236, Accra, Ghana. alexooo@yahoo.com

BACKGROUND: Change of first-line treatment of uncomplicated malaria to artemisinin-combination therapy (ACT) is widespread in Africa. To expand knowledge of safety profiles of ACT, pharmacovigilance activities are included in the implementation process of therapy changes. Ghana implemented first-line therapy of artesunate-amodiaquine in 2005. Drug utilization data is an important component of determining drug safety, and this paper describes how anti-malarials were prescribed within a prospective pharmacovigilance study in Ghana following anti-malarial treatment policy change. METHODS: Patients with diagnosis of uncomplicated malaria were recruited from pharmacies of health facilities throughout Accra in a cohort-event monitoring study. The main drug utilization outcomes were the relation of patient age, gender, type of facility attended, mode of diagnosis and concomitant treatments to the anti-malarial regimen prescribed. Logistic regression was used to predict prescription of nationally recommended first-line therapy and concomitant prescription of antibiotics. RESULTS: The cohort comprised 2,831 patients. Curative regimens containing an artemisinin derivative were given to 90.8% (n = 2,574) of patients, although 33% (n = 936) of patients received an artemisinin-based monotherapy. Predictors of first-line therapy were laboratory-confirmed diagnosis, age >5 years, and attending a government facility. Analgesics and antibiotics were the most commonly prescribed concomitant medications, with a median of two co-prescriptions per patient (range 1-9). Patients above 12 years were significantly less likely to have antibiotics co-prescribed than patients under five years; those prescribed non-artemisinin monotherapies were more likely to receive antibiotics. A dihydroartemisinin-amodiaquine combination was the most used therapy for children under five years of age (29.0%, n = 177). CONCLUSION: This study shows that though first-line therapy recommendations may change, clinical practice may still be affected by factors other than the decision or ability to diagnose malaria. Age, diagnostic confirmation and suspected concurrent conditions lead to benefit:risk assessments for individual patients by clinicians as to which anti-malarial treatment to prescribe. This has implications for adherence to policy changes aiming to implement effective use of ACT. These results should inform education of health professionals and rational drug use policies to reduce poly-pharmacy, and also suggest a potential positive impact of increased access to testing for malaria both within health facilities and in homes.

11: Malar J. 2008 Oct 27;7:218.

Human population, urban settlement patterns and their impact on Plasmodium falciparum malaria endemicity.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-218.pdf

Tatem AJ, Guerra CA, Kabaria CW, Noor AM, Hay SI.

Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK. andy.tatem@zoo.ox.ac.uk

BACKGROUND: The efficient allocation of financial resources for malaria control and the optimal distribution of appropriate interventions require accurate information on the geographic distribution of malaria risk and of the human populations it affects. Low population densities in rural areas and high population densities in urban areas can influence malaria transmission substantially. Here, the Malaria Atlas Project (MAP) global database of Plasmodium falciparum parasite rate (PfPR) surveys, medical intelligence and contemporary population surfaces are utilized to explore these relationships and other issues involved in combining malaria risk maps with those of human population distribution in order to define populations at risk more accurately. METHODS: First, an existing population surface was examined to determine if it was sufficiently detailed to be used reliably as a mask to identify areas of very low and very high population density as malaria free regions. Second, the potential of international travel and health guidelines (ITHGs) for identifying malaria free cities was examined. Third, the differences in PfPR values between surveys conducted in author-defined rural and urban areas were examined. Fourth, the ability of various global urban extent maps to reliably discriminate these author-based classifications of urban and rural in the PfPR database was investigated. Finally, the urban map that most accurately replicated the author-based classifications was analysed to examine the effects of urban classifications on PfPR values across the entire MAP database. RESULTS: Masks of zero population density excluded many non-zero PfPR surveys, indicating that the population surface was not detailed enough to define areas of zero transmission resulting from low population densities. In contrast, the ITHGs enabled the identification and mapping of 53 malaria free urban areas within endemic countries. Comparison of PfPR survey results showed significant differences between author-defined ‘urban’ and ‘rural’ designations in Africa, but not for the remainder of the malaria endemic world. The Global Rural Urban Mapping Project (GRUMP) urban extent mask proved most accurate for mapping these author-defined rural and urban locations, and further sub-divisions of urban extents into urban and peri-urban classes enabled the effects of high population densities on malaria transmission to be mapped and quantified. CONCLUSION: The availability of detailed, contemporary census and urban extent data for the construction of coherent and accurate global spatial population databases is often poor. These known sources of uncertainty in population surfaces and urban maps have the potential to be incorporated into future malaria burden estimates. Currently, insufficient spatial information exists globally to identify areas accurately where population density is low enough to impact upon transmission. Medical intelligence does however exist to reliably identify malaria free cities. Moreover, in Africa, urban areas that have a significant effect on malaria transmission can be mapped.

12: Malar J. 2008 Sep 16;7:178.

Malaria transmission in Dakar: a two-year survey.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-178.pdf

Pagès F, Texier G, Pradines B, Gadiaga L, Machault V, Jarjaval F, Penhoat K, Berger F, Trape JF, Rogier C, Sokhna C.

Unité d’Entomologie Médicale, Institut de Médecine Tropicale du Service de Santé des Armées, Marseille, France. frederic_pages@yahoo.com

BACKGROUND: According to entomological studies conducted over the past 30 years, there was low malaria transmission in suburb of Dakar but little evidence of it in the downtown area. However; there was some evidence of local transmission based on reports of malaria among permanent residents. An entomological
evaluation of malaria transmission was conducted from May 2005 to October 2006 in two areas of Dakar. METHODS: Mosquitoes were sampled by human landing collection during 34 nights in seven places in Bel-air area (238 person-nights) and during 24 nights in five places in Ouakam area (120 person-nights). Mosquitoes were identified morphologically and by molecular methods. The Plasmodium falciparum circumsporozoïte indexes were measured by ELISA, and the entomological inoculation rates (EIR) were calculated for both areas. Molecular assessments of pyrethroid knock down resistance (Kdr) and of insensitive acetylcholinesterase resistance were conducted. RESULTS: From May 2005 to October 2006, 4,117 and 797 Anopheles gambiae s.l. respectively were caught in Bel-air and Ouakam. Three members of the complex were present: Anopheles arabiensis (> 98%), Anopheles melas (< 1%) and An. gambiae s.s. molecular form M (< 1%). Infected mosquitoes were caught only during the wintering period between September and November in both places. In 2005 and 2006, annual EIRs were 9,5 and 4, respectively, in Bel-air and 3 and 3, respectively, in Ouakam. The proportion of host-seeking An. gambiae s.l. captured indoors were 17% and 51% in Bel air and Ouakam, respectively. Ace 1 mutations were not identified in both members of the An. gambiae complex. Kdr mutation frequency in An. arabiensis was 12% in Bel-air and 9% in Ouakam. CONCLUSION: Malaria is transmitted in Dakar downtown area. Infected mosquitoes were caught in two subsequent years during the wintering period in two distant quarters of Dakar. These data agree with clinical data from a Senegalese military Hospital of Dakar (Hospital Principal) where most malaria cases occurred between October and December. It was the first detection of An. melas in Dakar.

13: Malar J. 2008 Aug 4;7:151.

Impact of urban agriculture on malaria vectors in Accra, Ghana.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-151.pdf

Klinkenberg E, McCall P, Wilson MD, Amerasinghe FP, Donnelly MJ.

International Water Management Institute (IWMI), West Africa Office, Ghana.

To investigate the impact of urban agriculture on malaria transmission risk in urban Accra larval and adult stage mosquito surveys, were performed. Local transmission was implicated as Anopheles spp. were found breeding and infected Anopheles mosquitoes were found resting in houses in the study sites. The predominant Anopheles species was Anopheles gambiae s.s.. The relative proportion of molecular forms within a subset of specimens was 86% S-form and 14% M-form. Anopheles spp. and Culex quinquefasciatus outdoor biting rates were respectively three and four times higher in areas around agricultural sites (UA) than in areas far from agriculture (U). The annual Entomological Inoculation Rate (EIR), the number of infectious bites received per individual per year, was 19.2 and 6.6 in UA and U sites, respectively. Breeding sites were highly transitory in nature, which poses a challenge for larval control in this setting. The data also suggest that the epidemiological importance of urban agricultural areas may be the provision of resting sites for adults rather than an increased number of larval habitats. Host-seeking activity peaked between 2-3 am, indicating that insecticide-treated bednets should be an effective control method.

14: Malar J. 2008 Feb 29;7:39.

A census-weighted, spatially-stratified household sampling strategy for urban malaria epidemiology.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-39.pdf

Siri JG, Lindblade KA, Rosen DH, Onyango B, Vulule JM, Slutsker L, Wilson ML.

Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, Michigan, USA. jsiri@umich.edu

BACKGROUND: Urban malaria is likely to become increasingly important as a consequence of the growing proportion of Africans living in cities. A novel sampling strategy was developed for urban areas to generate a sample simultaneously representative of population and inhabited environments. Such a strategy should facilitate analysis of important epidemiological relationships in this ecological context. METHODS: Census maps and summary data for Kisumu, Kenya, were used to create a pseudo-sampling frame using the geographic coordinates of census-sampled structures. For every enumeration area (EA) designated as urban by the census (n = 535), a sample of structures equal to one-tenth the number of households was selected. In EAs designated as rural (n = 32), a geographically random sample totalling one-tenth the number of households was selected from a grid of points at 100 m intervals. The selected samples were cross-referenced to a geographic information system, and coordinates transferred to handheld global
positioning units. Interviewers found the closest eligible household to the sampling point and interviewed the caregiver of a child aged < 10 years. The demographics of the selected sample were compared with results from the Kenya Demographic and Health Survey to assess sample validity. Results were also compared among urban and rural EAs. RESULTS: 4,336 interviews were completed in 473 of the 567 study area EAs from June 2002 through February 2003. EAs without completed interviews were randomly distributed, and non-response was approximately 2%. Mean distance from the assigned sampling point to the completed interview was 74.6 m, and was significantly less in urban than rural EAs, even when controlling for number of households. The selected sample had significantly more children and females of childbearing age than the general population, and fewer older individuals. CONCLUSION: This method selected a sample that was simultaneously population-representative and inclusive of important environmental variation. The use of a pseudo-sampling frame and pre-programmed handheld GPS units is more efficient and may yield a more complete sample than traditional methods, and is less expensive than complete population enumeration.

15: Malar J. 2008 Feb 25;7:34.

Quantitative urban classification for malaria epidemiology in sub-Saharan Africa.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-34.pdf

Siri JG, Lindblade KA, Rosen DH, Onyango B, Vulule J, Slutsker L, Wilson ML.

Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, Michigan, USA. jsiri@umich.edu

BACKGROUND: Although sub-Saharan Africa (SSA) is rapidly urbanizing, the terms used to classify urban ecotypes are poorly defined in the context of malaria epidemiology. Lack of clear definitions may cause misclassification error, which likely decreases the accuracy of continent-wide estimates of malaria burden, limits the generalizability of urban malaria studies, and makes identification of high-risk areas for targeted interventions within cities more difficult. Accordingly, clustering techniques were applied to a set of urbanization- and malaria-related variables in Kisumu, Kenya, to produce a quantitative classification of the urban environment for malaria research. METHODS: Seven variables with a known or expected relationship with malaria in the context of urbanization were identified and measured at the census enumeration area (EA) level, using three sources: a) the results of a citywide knowledge, attitudes and practices (KAP) survey; b) a high-resolution multispectral satellite image; and c) national census data. Principal components analysis (PCA) was used to identify three factors explaining higher proportions of the combined variance than the original variables. A k-means clustering algorithm was applied to the EA-level factor scores to assign EAs to one of three categories: “urban,” “peri-urban,” or “semi-rural.” The results were compared with classifications derived from two other approaches: a) administrative designation of urban/rural by the census or b) population density thresholds. RESULTS: Urban zones resulting from the clustering algorithm were more geographically coherent than those delineated by population density. Clustering distributed population more evenly among zones than either of the other methods and more accurately predicted variation in other variables related to urbanization, but not used for classification. CONCLUSION: Effective urban malaria epidemiology and control would benefit from quantitative methods to identify and characterize urban areas. Cluster analysis techniques were used to classify Kisumu, Kenya, into levels of urbanization in a repeatable and unbiased manner, an approach that should permit more relevant comparisons among and within urban areas. To the extent that these divisions predict meaningful intra-urban differences in malaria epidemiology, they should inform targeted urban malaria interventions in cities across SSA.

16: Malar J. 2008 Jan 25;7:20.

A tool box for operational mosquito larval control: preliminary results and early lessons from the Urban Malaria Control Programme in Dar es Salaam, Tanzania.

Full-text: http://www.malariajournal.com/content/pdf/1475-2875-7-20.pdf

Fillinger U, Kannady K, William G, Vanek MJ, Dongus S, Nyika D, Geissbühler Y, Chaki PP, Govella NJ, Mathenge EM, Singer BH, Mshinda H, Lindsay SW, Tanner M, Mtasiwa D, de Castro MC, Killeen GF.

Durham University, School of Biological and Biomedical Sciences, South Road, Durham DH13LE, UK. ulrike.fillinger@durham.ac.uk

BACKGROUND: As the population of Africa rapidly urbanizes, large populations could be protected from malaria by controlling aquatic stages of mosquitoes if cost-effective and scalable implementation systems can be designed. METHODS: A recently initiated Urban Malaria Control Programme in Dar es Salaam delegates responsibility for routine mosquito control and surveillance to modestly-paid community members, known as Community-Owned Resource Persons (CORPs). New vector surveillance, larviciding and management systems were designed and evaluated in 15 city wards to allow timely collection, interpretation and reaction to entomologic monitoring data using practical procedures that rely on minimal technology. After one year of baseline data collection, operational larviciding with Bacillus thuringiensis var. israelensis commenced in March 2006 in three selected wards. RESULTS: The procedures and staff management systems described greatly improved standards of larval surveillance relative to that reported at the outset of this programme. In the first year of the programme, over 65,000 potential Anopheles habitats were surveyed by 90 CORPs on a weekly basis. Reaction times to vector surveillance at observations were one day, week and month at ward, municipal and city levels, respectively. One year of community-based larviciding reduced transmission by the primary malaria vector, Anopheles gambiae s.l., by 31% (95% C.I. = 21.6-37.6%; p = 0.04). CONCLUSION: This novel management, monitoring and evaluation system for implementing routine larviciding of malaria vectors in African cities has shown considerable potential for sustained, rapidly responsive, data-driven and affordable application. Nevertheless, the true programmatic value of larviciding in urban Africa can only be established through longer-term programmes which are stably financed and allow the operational teams and management infrastructures to mature by learning from experience.

Categories: Global
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