Participatory mapping of target areas to enable operational larval source management to suppress malaria vector mosquitoes in Dar es Salaam, Tanzania.
ABSTRACT: Half of the population of Africa will soon live in towns and cities where it can be protected from malaria by controlling aquatic stages of mosquitoes. Rigorous but affordable and scaleable methods for mapping and managing mosquito habitats are required to enable effective larval control in urban Africa.A simple community-based mapping procedure that requires no electronic devices in the field was developed to facilitate routine larval surveillance in Dar es Salaam, Tanzania. The mapping procedure included (1) community-based development of sketch maps and (2) verification of sketch maps through technical teams using laminated aerial photographs in the field which were later digitized and analysed using Geographical Information Systems (GIS).Three urban wards of Dar es Salaam were comprehensively mapped, covering an area of 16.8 km2. Over thirty percent of this area were not included in preliminary community-based sketch mapping, mostly because they were areas that do not appear on local government residential lists. The use of aerial photographs and basic GIS allowed rapid identification and inclusion of these key areas, as well as more equal distribution of the workload of malaria control field staff.The procedure developed enables complete coverage of targeted areas with larval control through comprehensive spatial coverage with community-derived sketch maps. The procedure is practical, affordable, and requires minimal technical skills. This approach can be readily integrated into malaria vector control programmes, scaled up to towns and cities all over Tanzania and adapted to urban settings elsewhere in Africa.
Project description:The use of larval source management is not prioritized by contemporary malaria control programs in sub-Saharan Africa despite historical success. Larviciding, in particular, could be effective in urban areas where transmission is focal and accessibility to Anopheles breeding habitats is generally easier than in rural settings. The objective of this study is to assess the effectiveness of a community-based microbial larviciding intervention to reduce the prevalence of malaria infection in Dar es Salaam, United Republic of Tanzania.Larviciding was implemented in 3 out of 15 targeted wards of Dar es Salaam in 2006 after two years of baseline data collection. This intervention was subsequently scaled up to 9 wards a year later, and to all 15 targeted wards in 2008. Continuous randomized cluster sampling of malaria prevalence and socio-demographic characteristics was carried out during 6 survey rounds (2004-2008), which included both cross-sectional and longitudinal data (N?=?64,537). Bayesian random effects logistic regression models were used to quantify the effect of the intervention on malaria prevalence at the individual level. Effect size estimates suggest a significant protective effect of the larviciding intervention. After adjustment for confounders, the odds of individuals living in areas treated with larviciding being infected with malaria were 21% lower (Odds Ratio?=?0.79; 95% Credible Intervals: 0.66-0.93) than those who lived in areas not treated. The larviciding intervention was most effective during dry seasons and had synergistic effects with other protective measures such as use of insecticide-treated bed nets and house proofing (i.e., complete ceiling or window screens).A large-scale community-based larviciding intervention significantly reduced the prevalence of malaria infection in urban Dar es Salaam.
Project description:The burden of stroke on health systems in low-income and middle-income countries is increasing. However, high-quality data for modifiable stroke risk factors in sub-Saharan Africa are scarce, with no community based, case-control studies previously published. We aimed to identify risk factors for stroke in an incident population from rural and urban Tanzania.Stroke cases from urban Dar-es-Salaam and the rural Hai district were recruited in a wider study of stroke incidence between June 15, 2003, and June 15, 2006. We included cases with fi rst-ever and recurrent stroke. Community-acquired controls recruited from the background census populations of the two study regions were matched with cases for age and sex and were interviewed and assessed. Data relating to medical and social history were recorded and blood samples taken.We included 200 stroke cases (69 from Dar-es-Salaam and 131 from Hai) and 398 controls (138 from Dar-es-Salaam and 260 from Hai). Risk factors were similar at both sites, with previous cardiac event (odds ratio [OR] 7.39, 95% CI 2.42-22.53; p<0.0001), HIV infection (5.61, 2.41-13.09; p<0.0001), a high ratio of total cholesterol to HDL cholesterol (4.54, 2.49-8.28; p<0.0001), smoking (2.72, 1.49-4.96; p=0.001), and hypertension (2.14, 1.09-4.17; p=0.026) identified as significant independent risk factors for stroke. In Hai, additional risk factors of diabetes (4.04, 1.29-12.64) and low HDL cholesterol (9.84, 4.06-23.84) were also significant.We have identified many of the risk factors for stroke already reported for other world regions. HIV status was an independent risk factor for stroke within an antiretroviral-naive population. Clinicians should be aware of the increased risk of stroke in people with HIV, even in the absence of antiretroviral treatment.
Project description:Rural-to-urban migration and intra-urban residential mobility often lead to improved living conditions. However, it is not clear if this is true for all, especially in cities in developing countries, where inequalities persist and upward mobility remains elusive for marginalized populations. We investigate the effects of intra-urban residential mobility and rural-to-urban migration on standards of living in Dar es Salaam, Tanzania. We examine the entire residential history of individuals and assess temporal changes in living conditions in their respective housing careers. We use four different aspects of housing as indicators of living conditions from a survey conducted by the World Bank Group that captured the residential history of 2,397 individuals in Dar es Salaam from a spatially representative sample of households. We find that improvements in housing conditions are uneven, a considerable proportion of individuals remained perpetually deprived of adequate housing despite migrating from rural areas to Dar es Salaam and changing multiple homes within the city during their tenure. Our findings indicate that housing disparities persist over time for many. Socioeconomic groups such as migrants tend to experience significant improvements after moving to the city but show limited upward mobility afterwards, an aspect that is rarely addressed in policy discourse on equitable access to adequate housing.
Project description:OBJECTIVE:To assess the dietary determinants of serum total cholesterol. DESIGN:Cross-sectional population-based study. SETTING:Peri-urban region of Dar es Salaam, Tanzania. PARTICIPANTS:347 adults aged 40 years and older from the Dar es Salaam Urban Cohort Hypertension Study. MAIN OUTCOME MEASURE:Serum total cholesterol measured using a point-of-care device. RESULTS:Mean serum total cholesterol level was 204?mg/dL (IQR 169-236?mg/dL) in women and 185?mg/dL (IQR 152-216?mg/dL) in men. After adjusting for demographic, socioeconomic, lifestyle and dietary factors, participants who reported using palm oil as the major cooking oil had serum total cholesterol higher by 15?mg/dL (95% CI 1 to 29?mg/dL) compared with those who reported using sunflower oil. Consumption of one or more servings of meat per day (p for trend=0.017) and less than five servings of fruits and vegetables per day (p for trend=0.024) were also associated with higher serum total cholesterol. A combination of using palm oil for cooking, eating more than one serving of meat per day and fewer than five servings of fruits and vegetables per day, was associated with 46?mg/dL (95% CI 16 to 76?mg/dL) higher serum total cholesterol. CONCLUSIONS:Using palm oil for cooking was associated with higher serum total cholesterol levels in this peri-urban population in Dar es Salaam. Reduction of saturated fat content of edible oil may be considered as a population-based strategy for primary prevention of cardiovascular diseases.
Project description:Objectives:To assess the patterns and incidence of child and adolescent injury and explore associations with household deprivation and child characteristics in a low-income urban setting. Study Design:Cross-sectional household survey in Dar es Salaam, Tanzania. Methods:Data collection took place during July 2009. Injuries requiring medical attention were recorded with a one month period of recall. A total of 1,968 households representing 3,927 children and adolescents were visited by health workers. Gender-, age-, and type-specific injury incidence was compiled. Odds ratios were calculated to measure associations with child injury, perceived deprivation, household characteristics and child characteristics. Results:One household in five reported injuries. The estimated incidence was 3.2 per 10,000 child-years. The most common identifiable injuries were falls (41%), cuts (22%) and burns (16%). Male and younger children aged 1-4 years were at higher risk (respectively OR = 1.36; p = 0.004; OR = 1.47; p ? 0.001). Conclusions:In Dar e Salaam injuries are common. Future investigations should take into account both subjective and objective measurements of relative household deprivation and a clear criteria for the assessment of injury severity in community-based survey contexts.
Project description:Preventing malaria by controlling mosquitoes in their larval stages requires regular sensitive monitoring of vector populations and intervention coverage. The study assessed the effectiveness of operational, community-based larval habitat surveillance systems within the Urban Malaria Control Programme (UMCP) in urban Dar es Salaam, Tanzania.Cross-sectional surveys were carried out to assess the ability of community-owned resource persons (CORPs) to detect mosquito breeding sites and larvae in areas with and without larviciding. Potential environmental and programmatic determinants of habitat detection coverage and detection sensitivity of mosquito larvae were recorded during guided walks with 64 different CORPs to assess the accuracy of data each had collected the previous day.CORPs reported the presence of 66.2% of all aquatic habitats (1,963/2,965), but only detected Anopheles larvae in 12.6% (29/230) of habitats that contained them. Detection sensitivity was particularly low for late-stage Anopheles (2.7%, 3/111), the most direct programmatic indicator of malaria vector productivity. Whether a CORP found a wet habitat or not was associated with his/her unfamiliarity with the area (Odds Ratio (OR) [95% confidence interval (CI)] = 0.16 [0.130, 0.203], P < 0.001), the habitat type (P < 0.001) or a fence around the compound (OR [95%CI] = 0.50 [0.386, 0.646], P < 0.001). The majority of mosquito larvae (Anophelines 57.8% (133/230) and Culicines 55.9% (461/825) were not reported because their habitats were not found. The only factor affecting detection of Anopheline larvae in habitats that were reported by CORPs was larviciding, which reduced sensitivity (OR [95%CI] = 0.37 [0.142, 0.965], P = 0.042).Accessibility of habitats in urban settings presents a major challenge because the majority of compounds are fenced for security reasons. Furthermore, CORPs under-reported larvae especially where larvicides were applied. This UMCP system for larval surveillance in cities must be urgently revised to improve access to enclosed compounds and the sensitivity with which habitats are searched for larvae.
Project description:BACKGROUND:Malaria control in Africa is most tractable in urban settlements yet most research has focused on rural settings. Elimination of malaria transmission from urban areas may require larval control strategies that complement adult mosquito control using insecticide-treated nets or houses, particularly where vectors feed outdoors. METHODS AND FINDINGS:Microbial larvicide (Bacillus thuringiensis var. israelensis (Bti)) was applied weekly through programmatic, non-randomized community-based, but vertically managed, delivery systems in urban Dar es Salaam, Tanzania. Continuous, randomized cluster sampling of malaria infection prevalence and non-random programmatic surveillance of entomological inoculation rate (EIR) respectively constituted the primary and secondary outcomes surveyed within a population of approximately 612,000 residents in 15 fully urban wards covering 55 km(2). Bti application for one year in 3 of those wards (17 km(2) with 128,000 residents) reduced crude annual transmission estimates (Relative EIR [95% Confidence Interval] = 0.683 [0.491-0.952], P = 0.024) but program effectiveness peaked between July and September (Relative EIR [CI] = 0.354 [0.193 to 0.650], P = 0.001) when 45% (9/20) of directly observed transmission events occurred. Larviciding reduced malaria infection risk among children < or =5 years of age (OR [CI] = 0.284 [0.101 to 0.801], P = 0.017) and provided protection at least as good as personal use of an insecticide treated net (OR [CI] = 0.764 [0.614-0.951], P = 0.016). CONCLUSIONS:In this context, larviciding reduced malaria prevalence and complemented existing protection provided by insecticide-treated nets. Larviciding may represent a useful option for integrated vector management in Africa, particularly in its rapidly growing urban centres.
Project description:Young people in sub-Saharan Africa are affected by the HIV pandemic to a greater extent than young people elsewhere and effective HIV-preventive intervention programmes are urgently needed. The present article presents the rationale behind an EU-funded research project (PREPARE) examining effects of community-based (school delivered) interventions conducted in four sites in sub-Saharan Africa. One intervention focuses on changing beliefs and cognitions related to sexual practices (Mankweng, Limpopo, South Africa). Another promotes improved parent-offspring communication on sexuality (Kampala, Uganda). Two further interventions are more comprehensive aiming to promote healthy sexual practices. One of these (Western Cape, South Africa) also aims to reduce intimate partner violence while the other (Dar es Salaam, Tanzania) utilises school-based peer education.A modified Intervention Mapping approach is used to develop all programmes. Cluster randomised controlled trials of programmes delivered to school students aged 12-14 will be conducted in each study site. Schools will be randomly allocated (after matching or stratification) to intervention and delayed intervention arms. Baseline surveys at each site are followed by interventions and then by one (Kampala and Limpopo) or two (Western Cape and Dar es Salaam) post-intervention data collections. Questionnaires include questions common for all sites and are partly based on a set of social cognition models previously applied to the study of HIV-preventive behaviours. Data from all sites will be merged in order to compare prevalence and associations across sites on core variables. Power is set to .80 or higher and significance level to .05 or lower in order to detect intervention effects. Intraclass correlations will be estimated from previous surveys carried out at each site.We expect PREPARE interventions to have an impact on hypothesized determinants of risky sexual behaviour and in Western Cape and Dar es Salaam to change sexual practices. Results from PREPARE will (i) identify modifiable cognitions and social processes related to risky sexual behaviour and (ii) identify promising intervention approaches among young adolescents in sub-Saharan cultures and contexts.Controlled Trials ISRCTN56270821 (Cape Town); Controlled Trials ISRCTN10386599 (Limpopo); Clinical Trials NCT01772628 (Kampala); Australian New Zealand Clinical Trials Registry ACTRN12613000900718 (Dar es Salaam).
Project description: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.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.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).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.
Project description:BACKGROUND:Delayed vaccination increases the time infants are at risk for acquiring vaccine-preventable diseases. Factors associated with incomplete vaccination are relatively well characterized in resource-limited settings; however, few studies have assessed immunization timeliness. METHODS:We conducted a prospective cohort study examining Diphtheria-Tetanus-Pertussis (DTP) vaccination timing among newborns enrolled in a Neonatal Vitamin A supplementation trial (NEOVITA) conducted in urban Dar es Salaam (n = 11,189) and rural Morogoro Region (n = 19,767), Tanzania. We used log-binomial models to assess the relationship of demographic, socioeconomic, healthcare access, and birth characteristics with late or incomplete DTP1 and DTP3 immunization. RESULTS:The proportion of infants with either delayed or incomplete vaccination was similar in Dar es Salaam (DTP1 11.5% and DTP3 16.0%) and Morogoro (DTP1 9.2% and DTP3 17.3%); however, the determinants of delayed or incomplete vaccination as well as their magnitude of association differed by setting. Both maternal and paternal education were more strongly associated with vaccination status in rural Morogoro region as compared to Dar es Salaam (p-values for heterogeneity < 0.05). Infants in Morogoro who had fathers and mothers with no education had 36% (95% CI: 22-52%) and 22% (95% CI: 10-34%) increased risk of delayed or incomplete DTP3 vaccination as compared to those with primary school education, respectively. In Dar es Salaam, mothers who attended their first antenatal care (ANC) visit in the 3rd trimester had 1.55 (95% CI: 1.36-1.78) times the risk of delayed or not received vaccination as compared to those with a 2nd trimester booking, while there was no relationship in Morogoro. In rural Morogoro, infants born at home had 17% (95% CI: 8-27%) increased risk for delayed or no receipt of DTP3 vaccination. In both settings, younger maternal age and poorer households were at increased risk for delayed or incomplete vaccination. CONCLUSION:We found some risk factors for delayed and incomplete vaccination were shared between urban and rural Tanzania; however, we found several context-specific risk factors as well as determinants that differed in their magnitude of risk between contexts. Immunization programs should be tailored to address context-specific barriers and enablers to improve timely and complete vaccination.