Informal Urban Settlements and Cholera Risk in Dar es Salaam,Tanzania

Background

As a result of poor economic opportunities and an increasing shortage of affordable housing, much of the spatial growth in many of the world''s fastest-growing cities is a result of the expansion of informal settlements where residents live without security of tenure and with limited access to basic infrastructure. Although inadequate water and sanitation facilities, crowding and other poor living conditions can have a significant impact on the spread of infectious diseases, analyses relating these diseases to ongoing global urbanization, especially at the neighborhood and household level in informal settlements, have been infrequent. To begin to address this deficiency, we analyzed urban environmental data and the burden of cholera in Dar es Salaam, Tanzania.

Methodology/Principal Findings

Cholera incidence was examined in relation to the percentage of a ward''s residents who were informal, the percentage of a ward''s informal residents without an improved water source, the percentage of a ward''s informal residents without improved sanitation, distance to the nearest cholera treatment facility, population density, median asset index score in informal areas, and presence or absence of major roads. We found that cholera incidence was most closely associated with informal housing, population density, and the income level of informal residents. Using data available in this study, our model would suggest nearly a one percent increase in cholera incidence for every percentage point increase in informal residents, approximately a two percent increase in cholera incidence for every increase in population density of 1000 people per km² in Dar es Salaam in 2006, and close to a fifty percent decrease in cholera incidence in wards where informal residents had minimally improved income levels, as measured by ownership of a radio or CD player on average, in comparison to wards where informal residents did not own any items about which they were asked. In this study, the range of access to improved sanitation and improved water sources was quite narrow at the ward level, limiting our ability to discern relationships between these variables and cholera incidence. Analysis at the individual household level for these variables would be of interest.

Conclusions/Significance

Our results suggest that ongoing global urbanization coupled with urban poverty will be associated with increased risks for certain infectious diseases, such as cholera, underscoring the need for improved infrastructure and planning as the world''s urban population continues to expand.     

Bioconversion of lignocellulosic waste from selected dumping sites in Dar es Salaam,Tanzania

The poor management of solid wastes in Tanzania urban centers is a chronic problem that has increasingly become a source of environmental pollution. Bioconversion offers a cheap and safe method of not only disposing these wastes, but also it has the potential to convert lignocellulosic wastes into usable forms such as reducing sugars that could be used as food. This paper reports a preliminary study on the physical characteristics, acid pretreatment, saccharification by cellulase from Trichoderma reesei and fermentation by Saccharomyces cerevisiae of the lignocellulosic component of the solid wastes collected from various dumping sites located in Kinondoni Municipality, Dar es Salaam city. The results showed that overall, the lignocellulosic component constitute about 50% of solid wastes dumped in the study areas. Maximum production of reducing sugars was obtained after 6 h of saccharification while highest concentrations of bioethanol were achieved after 48 h of fermentation. Microbial bioconversion of lignocellulose component yielded up to 21% bioethanol.     

Impact of Community-Based Larviciding on the Prevalence of Malaria Infection in Dar es Salaam,Tanzania

Background

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.

Methods and Findings

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).

Conclusion

A large-scale community-based larviciding intervention significantly reduced the prevalence of malaria infection in urban Dar es Salaam.     

Prospective study of incidence of juvenile diabetes mellitus over 10 years in Dar es Salaam,Tanzania.

OBJECTIVE--To ascertain the annual incidence of diabetes requiring treatment with insulin in children and adolescents aged 0-19 years in Dar es Salaam, Tanzania, during a 10 year period from 1 January 1982 to 31 December 1991. DESIGN--Prospective registration at a major urban hospital of all patients with newly diagnosed diabetes who were resident in Dar es Salaam. SETTING--Muhimbili Medical Centre, Dar es Salaam, Tanzania. PATIENTS--86 patients: 45 male, 41 female. RESULTS--The annual incidence of juvenile diabetes for both sexes was 1.5 per 100,000 population aged 0-19 years (95% confidence interval 1.3 to 1.7). Incidence per 100,000 population per year increased with age: 0.6 (0.0 to 0.13) in the age group 0-4 years, 0.5 (0.3 to 0.7) at 5-9 years, 2.2 (1.8 to 2.6) at 10-14 years, and 3.4 (2.9 to 3.9) at 15-19 years. CONCLUSION--Juvenile diabetes mellitus is fairly rare in sub-Saharan Africa. If environmental factors such as infection and material deprivation were important determinants of insulin dependent diabetes in Africans, as they may be in Europeans, much higher rates would have been expected unless genetic factors possibly exert a protective role. The eightfold greater incidence in African Americans than in Tanzanians may be related to greater genetic admixture in African Americans with people from countries in Europe with a high incidence.     

The diet of the edible cockle Anadara antiquata L. (Bivalvia,Arcidae) in Dar es Salaam,Tanzania, during the northeast monsoons

The diet of the cockle Anadara antiquata L. was studied along Dar es Salaam coast during the N-E Monsoon season. No zooplankton were found in the 80 cockle guts examined. 27 phytoplankton genera were identified, an indication of wide phytophagy. Members of classes Bacillariophyceae, Chlorophyceae, Pyrophyceae and Prasnophyceae were very prevalent in the diet. Scenedesmus, Chlamydomonas, Palmeria, Exuviella, and Coscinodiscus showed the highest recurrence frequencies per gut.     

Personal protection against mosquitoes in Dar es Salaam,Tanzania, by using a kerosene oil lamp to vaporize transfluthrin

The effectiveness of a cheap and easy method of household protection against Culex quinquefasciatus Say and other mosquitoes (Diptera: Culicidae) was investigated in Dar es Salaam, Tanzania. Kerosene-burning lamps (korobois) were modified to heat and vaporize transfluthrin, a volatile pyrethroid insecticide. When transfluthrin was added to fuel of the lamp, protection against biting was poor unless a very high concentration of insecticide was used. A modified lamp (= vaporizing koroboi) was designed to overcome this problem by mixing the insecticide with vegetable oil and heating it to 120 degrees C in a tin held just above the flame. The concentration of 0.1% transfluthrin in vegetable oil gave 50-75% reduction in biting, a similar degree of protection to that obtained from burning a mosquito coil containing a synthetic pyrethroid (0.25% d-allethrin) and significantly better protection than a locally bought coil (brand 'White Crane', probably containing DDT). Greater protection (consistently > 90%) was achieved with a higher concentration of transfluthrin (0.5%) in the vegetable oil. This modified lamp is simple, cheap and employs locally available technology. With further development, and due regard to inhalation toxicity of the vaporized materials, it may offer a more cost-effective alternative to a mosquito coil as a means of personal protection, and a useful complement to a net for the early part of the evening before bedtime.     

A first insight into the genetic diversity of Mycobacterium tuberculosis in Dar es Salaam, Tanzania, assessed by spoligotyping

Background  

Tanzania has a high tuberculosis incidence, and genotyping studies of Mycobacterium tuberculosis in the country are necessary in order to improve our understanding of the epidemic. Spoligotyping is a potentially powerful genotyping method due to fast generation of genotyping results, high reproducibility and low operation costs. The recently constructed SpolDB4 database and the model-based program 'spotclust' can be used to assign isolates to families, subfamilies and variants. The results of a study can thus be analyzed in a global context.     

Identifying Programmatic Gaps: Inequities in Harm Reduction Service Utilization among Male and Female Drug Users in Dar es Salaam,Tanzania

Introduction

Current estimates suggest an HIV prevalence of 42% among people who inject drugs (PWIDs) in Dar es Salaam, while HIV prevalence is estimated to be 8.8% among the general population in the city. To address the HIV epidemic in this population, the government of Tanzania began establishing HIV prevention, treatment and care services including outreach and medication assisted treatment (MAT) for PWIDs in 2010. We assessed gender inequities in utilization of outreach and MAT services and evaluated differences in HIV risk behaviors between female and male PWIDs.

Materials and Methods

Routine outreach data between December 2010 to mid-August 2012 and baseline data on clients enrolling in methadone from February 2011 to August 2012 were utilized. Binomial regression was used to estimate adjusted relative risk estimates comparing females to males.

Results

From December 2010 to August 2012, 8,578 contacts were made to drug users; among them 1,898 were injectors. A total of 453 injectors were eligible and referred to MAT, of which, 443 enrolled in treatment. However, regarding total outreach contacts, outreach to PWID, referral to MAT and enrollment in MAT, 8% or less of drug users accessing services were women. In contrast, weighted estimations from surveys suggest that 34% of PWIDs are female, and this approximation is similar to recent population size estimations. Overall, 43% of traditional outreach workers conducting outreach with drug users were female. Though reporting higher levels of condom usage, female PWID were more likely to report multiple sex partners, anal sex, commercial sex work and struggle under a higher burden of addiction, mental disorders and abuse.

Conclusions

Services have not been mobilized adequately to address the clear needs of females who inject drugs. A clear and urgent need exists for women-centered strategies that effectively engage female PWID into HIV prevention services.     

Prevalence of Cryptosporidium parvum/hominis,Entamoeba histolytica and Giardia lamblia among Young Children with and without Diarrhea in Dar es Salaam,Tanzania

Background

Although enteroparasites are common causes of diarrheal illness, few studies have been performed among children in Tanzania. This study aimed to investigate the prevalence of Cryptosporidium parvum/hominis, Entamoeba histolytica and Giardia lamblia among young children in Dar es Salaam, Tanzania, and identify risk factors for infection.

Methodology/Principal Findings

We performed an unmatched case-control study among children < 2 years of age in Dar es Salaam, recruited from August 2010 to July 2011. Detection and identification of protozoans were done by PCR techniques on DNA from stool specimens from 701 cases of children admitted due to diarrhea at the three study hospitals, and 558 controls of children with no history of diarrhea during the last month prior to enrollment. The prevalence of C. parvum/hominis was 10.4% (84.7% C. hominis), and that of G. lamblia 4.6%. E. histolytica was not detected. The prevalence of Cryptosporidium was significantly higher in cases (16.3%) than in controls (3.1%; P < 0.001; OR = 6.2; 95% CI: 3.7–10.4). G. lamblia was significantly more prevalent in controls (6.1%) than in cases (3.4%; P = 0.027; OR = 1.8; 95% CI: 1.1–3.1). Cryptosporidium infection was found more often in HIV-positive (24.2%) than in HIV-negative children (3.9%; P < 0.001; OR = 7.9; 95% CI: 3.1–20.5), and was also associated with rainfall (P < 0.001; OR = 2.41; 95% CI: 1.5–3.8). Among cases, stunted children had significantly higher risk of being infected with Cryptosporidium (P = 0.011; OR = 2.12; 95% CI: 1.2–3.8). G. lamblia infection was more prevalent in the cool season (P = 0.004; OR = 2.2; 95% CI: 1.3–3.8), and more frequent among cases aged > 12 months (P = 0.003; OR = 3.5; 95% CI: 1.5–7.8). Among children aged 7–12 months, those who were breastfed had lower prevalence of G. lamblia infection than those who had been weaned (P = 0.012).

Conclusions

Cryptosporidium infection is common among young Tanzanian children with diarrhea, particularly those living with HIV, and infection is more frequent during the rainy season. G. lamblia is frequently implicated in asymptomatic infections, but rarely causes overt diarrheal illness, and its prevalence increases with age.     

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

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.     

Diabetes in tropical Africa: a prospective study, 1981-7. I. Characteristics of newly presenting patients in Dar es Salaam,Tanzania, 1981-7.

OBJECTIVE--To study the clinical characteristics of newly diagnosed diabetic patients in tropical Africa. DESIGN--Prospective study of all newly diagnosed diabetic patients registered at a major urban hospital between 1 June 1981 and 31 May 1987. SETTING--Muhimbili Medical Centre, Dar es Salaam, Tanzania. PATIENTS--1250 Patients: 874 men, 376 women. RESULTS--272 (21.8%) Patients had diabetes requiring insulin, 825 (66.0%) had diabetes not requiring insulin, and 153 (12.2%) had diabetes of uncertain type. Most patients (1103, 88.2%) presented with the classic symptoms of diabetes. The peak time of presentation of diabetic patients requiring insulin was at age 15 to 19 years. Male manual workers and peasant farmers with diabetes not requiring insulin presented at a significantly older age and had a lower body mass index than sedentary office workers. Forty six (18.1%) of the patients requiring insulin diabetes and 111 (14.4%) not requiring insulin had first degree relative with diabetes. Twenty seven per cent of patients were underweight (body mass index less than 20 kg/m2) and 14.6% were obese (body mass index greater than 30 kg/m2). Hypertension was diagnosed in 211 (26.7%) of 791 patients not requiring insulin. Nine (3.3%) of those requiring insulin may have had the protein deficient type of diabetes related to malnutrition. The fibrocalculous variety of diabetes related to malnutrition was not observed. CONCLUSIONS--Newly presenting diabetic patients in Tanzania with diabetes requiring insulin are older at presentation than those in Britain; most diabetic patients present with diabetes not requiring insulin and a smaller proportion of Tanzanian patients are obese. Most have a lower socioeconomic state than diabetic patients in Britain. There are often delays in diagnosis in Tanzania, and there is a higher incidence of death shortly after presentation.     

Low quality of routine microscopy for malaria at different levels of the health system in Dar es Salaam

Background

Laboratory capacity to confirm malaria cases in Tanzania is low and presumptive treatment of malaria is being practiced widely. In malaria endemic areas WHO now recommends systematic laboratory testing when suspecting malaria. Currently, the use of Rapid Diagnostic Tests (RDTs) is recommended for the diagnosis of malaria in lower level peripheral facilities, but not in health centres and hospitals. In this study, the following parameters were evaluated: (1) the quality of routine microscopy, and (2) the effects of RDT implementation on the positivity rate of malaria test results at three levels of the health system in Dar es Salaam, Tanzania.

Methods

During a baseline cross-sectional survey, routine blood slides were randomly picked from 12 urban public health facilities in Dar es Salaam, Tanzania. Sensitivity and specificity of routine slides were assessed against expert microscopy. In March 2007, following training of health workers, RDTs were introduced in nine public health facilities (three hospitals, three health centres and three dispensaries) in a near-to-programmatic way, while three control health facilities continued using microscopy. The monthly malaria positivity rates (PR) recorded in health statistics registers were collected before (routine microscopy) and after (routine RDTs) the intervention in all facilities.

Results

At baseline, 53% of blood slides were reported as positive by the routine laboratories, whereas only 2% were positive by expert microscopy. Sensitivity of routine microscopy was 71.4% and specificity was 47.3%. Positive and negative predictive values were 2.8% and 98.7%, respectively. Median parasitaemia was only three parasites per 200 white blood cells (WBC) by routine microscopy compared to 1226 parasites per 200 WBC by expert microscopy. Before RDT implementation, the mean test positivity rates using routine microscopy were 43% in hospitals, 62% in health centres and 58% in dispensaries. After RDT implementation, mean positivity rates using routine RDTs were 6%, 7% and 8%, respectively. The sensitivity and specificity of RDTs using expert microscopy as reference were 97.0% and 96.8%. The positivity rate of routine microscopy remained the same in the three control facilities: 71% before versus 72% after. Two cross-sectional health facility surveys confirmed that the parasite rate in febrile patients was low in Dar es Salaam during both the rainy season (13.6%) and the dry season (3.3%).

Conclusions

The quality of routine microscopy was poor in all health facilities, regardless of their level. Over-diagnosis was massive, with many false positive results reported as very low parasitaemia (1 to 5 parasites per 200 WBC). RDTs should replace microscopy as first-line diagnostic tool for malaria in all settings, especially in hospitals where the potential for saving lives is greatest.

     

Synchrony of Sylvatic Dengue Isolations: A Multi-Host,Multi-Vector SIR Model of Dengue Virus Transmission in Senegal

Isolations of sylvatic dengue-2 virus from mosquitoes, humans and non-human primates in Senegal show synchronized multi-annual dynamics over the past 50 years. Host demography has been shown to directly affect the period between epidemics in other pathogen systems, therefore, one might expect unsynchronized multi-annual cycles occurring in hosts with dramatically different birth rates and life spans. However, in Senegal, we observe a single synchronized eight-year cycle across all vector species, suggesting synchronized dynamics in all vertebrate hosts. In the current study, we aim to explore two specific hypotheses: 1) primates with different demographics will experience outbreaks of dengue at different periodicities when observed as isolated systems, and that coupling of these subsystems through mosquito biting will act to synchronize incidence; and 2) the eight-year periodicity of isolations observed across multiple primate species is the result of long-term cycling in population immunity in the host populations. To test these hypotheses, we develop a multi-host, multi-vector Susceptible, Infected, Removed (SIR) model to explore the effects of coupling multiple host-vector systems of dengue virus transmission through cross-species biting rates. We find that under small amounts of coupling, incidence in the host species synchronize. Long-period multi-annual dynamics are observed only when prevalence in troughs reaches vanishingly small levels (), suggesting that these dynamics are inconsistent with sustained transmission in this setting, but are consistent with local dengue virus extinctions followed by reintroductions. Inclusion of a constant introduction of infectious individuals into the system causes the multi-annual periods to shrink, while the effects of coupling remain the same. Inclusion of a stochastic rate of introduction allows for multi-annual periods at a cost of reduced synchrony. Thus, we conclude that the eight-year period separating amplifications of dengue may be explained by cycling in immunity with stochastic introductions.     

Epidemiological and Molecular Characterization of Dengue Virus Circulating in Bhutan, 2013-2014

Dengue is one of the most significant public health problems in tropical and subtropical countries, and is increasingly being detected in traditionally non-endemic areas. In Bhutan, dengue virus (DENV) has only recently been detected and limited information is available. In this study, we analyzed the epidemiological and molecular characteristics of DENV in two southern districts in Bhutan from 2013–2014. During this period, 379 patients were clinically diagnosed with suspected dengue, of whom 119 (31.4%) were positive for DENV infection by NS1 ELISA and/or nested RT-PCR. DENV serotypes 1, 2 and 3 were detected with DENV-1 being predominant. Phylogenetic analysis of DENV-1 using envelope gene demonstrated genotype V, closely related to strains from northern India.