Understanding the epidemiology and transmission of tuberculosis among adults in rural and urban Tanzania

Background: Tuberculosis (TB) is the leading cause of death in the world from a single infectious disease and resulted in about 1.5 million deaths in 2018. Globally, close to one third of the population is latently infected with Mycobacterium tuberculosis (Mtb), of which about 5-10% during their lifetime, will develop active TB depending on the age of infection. TB is an airborne disease transmitted by airways from one person to the next when an uninfected individual breathes in air containing Mtb expired from an infected person. One way to estimate the risk of TB transmission begins with measuring environmental levels of carbon dioxide (CO2) levels exhaled by humans. CO2 levels combined with social contact data allow calculation of the volumes of rebreathed air in order to estimate the potential for airborne disease transmission by considering time at risk, quanta of contagion and the number of people occupying the confined space etc. Unfortunately, most TB patients are diagnosed at later stages of the disease, due to poor health-seeking behavior, inappropriate diagnostic investigations requested by health care providers, and limited access to better TB diagnostics which forces patients to seek relief by using self-prescribed medication. Delaying diagnosis and treatment of TB has important consequences for disease control at both the individual (poor treatment outcome) as well as the community level (continued transmission). Within the country, the prevalence of TB varies considerably across regions, and is higher among males, older persons, and those with lower socioeconomic status. Lastly, patients with TB often have additional comorbidities such as anemia, helminthiasis etc., which can result in poor treatment outcomes. Anemia of chronic disease is primarily found in patients with chronic disease status such as those with chronic immune activation such as TB and HIV-positive patients. Objectives: The overall goal of this PhD project was to understand the epidemiology and transmission of tuberculosis in Tanzania by studying the infrastructure-related risk of TB transmission through measuring environmental CO2 levels at locations of public importance; determining the TB diagnostic delay and its associated factors among TB patients; understanding differences in the epidemiology of TB and comorbidities among TB patients from rural and urban Tanzania; and investigating the association of hepcidin levels with coinfections, TB disease severity and progression from TB infection to disease among adults in Tanzania. Methods: This PhD project was embedded in the ongoing hospital-based cohort of adult TB cases and controls in Temeke, Dar es Salaam and Ifakara, Morogoro, Tanzania. The field work for this PhD study was carried out between September 2016 and April 2018. The project had two designs; infrastructure-related and patient-related design. For objective 1, an observational study was carried out which employed exposure assessment methods where we collected environmental data (CO2, geo-coordinates etc.,) from locations of public importance. We used the modified Wells-Riley equation to estimate the annual risk of TB transmission which was calculated as a function of time spent per year at a given location. For objectives 2-3, we analysed data from the ongoing cohort of adult TB patients and their household contacts (TB DAR). Briefly, recruitment of study participants began in 2013 at Temeke Regional Referral Hospital (Temeke district) and 2014 at the St. Francis Referral Hospital (Kilombero district). Participants collected baseline information and provided specimen for further analysis. Multivariate logistic regression models were used to find associations and presented as crude and adjusted odds ratio. Lastly, for objective 4, we designed a nested case-control study matched by age and sex. Descriptive statistics were used to summarize participants characteristics. We compared cases and controls using conditional logistic regression model to determine associations between outcomes of interest and various predictors. Results: We found that the annual risks of TB transmission were highest among prison inmates (41.6%) and drivers (20.3%) in public transport. Lower transmission risks were found in central markets (4.8% for traders, but 0.5% for their customers), passengers on public transport (2.4%), public schools (4.0%), nightclubs (1.7%), religious (0.13%), and social halls (0.12%). Diagnostic delay was positively associated with absence of chest pain (aOR = 7.97, 95% confidence intervals [CI] = 3.15 – 20.19), and presence of hemoptysis (aOR = 25.37, 95% CI = 11.15 – 57.74) and negatively associated with use of medication prior to TB diagnosis (aOR = 0.31, 95% CI = 0.14 – 0.71). Patients living far from pharmacies were less likely to visit a health care facility (incremental increase of distance versus visit to any facility: OR = 0.51, 95% CI = 0.28 – 0.96). Patients from the rural setting were older (median age 37 years vs. 34 years, p=0.003), had a lower median body mass index (17.5 kg/m2 vs. 18.5 kg/m2, p<0.001), a higher proportion of recurrent TB cases (9% vs. 1%, p<0.001) compared to those from urban Tanzania. The overall prevalence of helminth co-infections was 22.9% with differences in the etiology of helminthiasis. The higher prevalence of helminthiasis in the urban setting (25.7% vs. 17.3%, p=0.018) was predominantly driven by Strongyloides stercoralis (17.0% vs. 4.8%, p<0.001) while Schistosoma mansoni infection (4.1% vs. 16.4%, p<0.001) dominated in the rural setting. Recurrent TB was associated with living in a rural setting (adjusted odds ratio [aOR] 3.97, 95% CI 1.16-13.67) and increasing age (aOR 1.06, 95% CI 1.02-1.10). Anemia of chronic disease (ACD) was more frequent among cases than controls (59.8% vs. 26.1%), but iron-deficiency anemia more frequent in controls (10% vs. 1%). The median hepcidin level was higher in cases than controls (63.7 vs. 14.2 ng/mL), but coinfections with HIV, helminths, and respiratory pathogens did not show cumulative effects. Hepcidin was associated with more severe TB symptom scoring (coefficient 0.8, 95% confidence interval [CI] 0.5-1.2) and higher mycobacterial load (0.7, 95% CI 0.4-1.0). Hepcidin was higher in TB cases and controls who developed TB compared to controls without TB (p<0.001), even when restricting to HIV-negative study participants. Conclusions: From this PhD project, we have demonstrated that environmental CO2 from locations of public importance, could identify locations with higher risk of TB transmission. This novel approach can be used by National TB Programs (NTP) to guide targeted infection control interventions for TB control in sub-Saharan Africa to reduce TB transmission. Adults from urban Tanzania, are still faced with significant TB diagnosis delay and that the use of medication prior to TB diagnosis was common. This provides a unique opportunity for inclusion of pharmacies in the formal referral systems from communities to TB diagnostic facilities. We found TB patients from rural Tanzania were likely to be older, with recurrent TB, with features of advanced TB disease due to a longer TB diagnosis delay and seek more frequently care from traditional healers. The overall prevalence of helminth co-infections among TB patients was higher in urban Tanzania, predominantly driven by Strongyloides stercoralis infection, but the prevalence of Schistosoma mansoni was higher in the rural Tanzania. NTPs should strive to understand fundamental differences in the TB epidemiology in different settings and translate that into specific interventions based on such differences. For example, the NTLP should build the capacity of traditional healers in rural Tanzania, for improving early detection of TB cases and referral for TB treatment. Lastly, we found hepcidin to be marginally upregulated by coinfections other than Mtb, and thus this could be used as a marker for identifying patient with severe TB disease and high-risk persons exposed to TB

Paraspinal Abscess Secondary to Tuberculous Spondylitis Diagnosed by Xpert MTB/RIF Assay in Rural Tanzania.

A 31-year-old HIV-negative man presented to our clinic with a 6-month history of back pain and a swelling at the back. Radiological studies revealed lumbar vertebral destruction. Ultrasound of the mass showed a septated cystic mass with turbid fluid. Diagnostic aspiration revealed thick pus and smear microscopy detected acid-fast bacilli. Xpert MTB/RIF assay detected Mycobacterium tuberculosis with no rifampicin resistance

Diagnostic Delay and Associated Factors among Patients with Pulmonary Tuberculosis in Dar es Salaam, Tanzania.

Tanzania is among the 30 countries with the highest tuberculosis (TB) burdens. Because TB has a long infectious period, early diagnosis is not only important for reducing transmission, but also for improving treatment outcomes. We assessed diagnostic delay and associated factors among infectious TB patients. We interviewed new smear-positive adult pulmonary TB patients enrolled in an ongoing TB cohort study in Dar es Salaam, Tanzania, between November 2013 and June 2015. TB patients were interviewed to collect information on socio-demographics, socio-economic status, health-seeking behaviour, and residential geocodes. We categorized diagnostic delay into ≤ 3 or > 3 weeks. We used logistic regression models to identify risk factors for diagnostic delay, presented as crude (OR) and adjusted Odds Ratios (aOR). We also assessed association between geographical distance (incremental increase of 500 meters between household and the nearest pharmacy) with binary outcomes. We analysed 513 patients with a median age of 34 years (interquartile range 27-41); 353 (69%) were men. Overall, 444 (87%) reported seeking care from health care providers prior to TB diagnosis, of whom 211 (48%) sought care > 2 times. Only six (1%) visited traditional healers before TB diagnosis. Diagnostic delay was positively associated with absence of chest pain (aOR = 7.97, 95% confidence intervals [CI]: 3.15-20.19; P < 0.001), and presence of hemoptysis (aOR = 25.37, 95% CI: 11.15-57.74; P < 0.001) and negatively associated with use of medication prior to TB diagnosis (aOR = 0.31, 95% CI: 0.14-0.71; P = 0.01). Age, sex, HIV status, education level, household income, and visiting health care facilities (HCFs) were not associated with diagnostic delay. Patients living far from pharmacies were less likely to visit a HCF (incremental increase of distance versus visit to any facility: OR = 0.51, 95% CI: 0.28-0.96; P = 0.037). TB diagnostic delay was common in Dar es Salaam, and was more likely among patients without prior use of medication and presenting with hemoptysis. Geographical distance to HCFs may have an impact on health-seeking behaviour. Increasing community awareness of TB signs and symptoms could further reduce diagnostic delays and interrupt TB transmission

Preservation of sputum samples with cetylpyridinium chloride (CPC) for tuberculosis cultures and Xpert MTB/RIF in a low-income country

Culture contamination with environmental bacteria is a major challenge in tuberculosis (TB) laboratories in hot and humid climate zones. We studied the effect of cetylpyridinium chloride (CPC) preservation on culture results and performance of Xpert MTB/RIF.; Consecutive sputum samples from microscopy smear-positive TB patients were collected. Two-hundred samples were equally split in two aliquots, one aliquot was treated with CPC and stored at ambient temperature for 7 days. The second aliquot was immediately processed. Samples were decontaminated for 20, 15 or 10 min, and subsequently cultured on Löwenstein-Jensen medium. Furthermore, 50 samples were stored for 7, 14 and 21 days, and 100 CPC-pretreated samples tested by Xpert MTB/RIF.; CPC pretreated samples showed a higher culture yield compared to non-treated sputum samples across all decontamination times: 94% vs. 73% at 10 min (p = 0.01), 94% vs. 64% at 15 min (p = 0.004), and 90% vs. 52% at 20 min (p &lt; 0.001). The quantitative culture grading was consistently higher in CPC treated compared to non-CPC treated samples. The proportion of contaminated cultures was lower in CPC pretreated samples across all decontamination times (range 2-6%) compared to non-CPC treated samples (15-16%). For storage times of CPC treated samples of 7, 14, and 21 days, 84, 86, and 84% of the respective cultures were positive. Of 91 CPC treated samples with a positive culture, 90 were also Xpert MTB/RIF positive.; CPC increases culture yield, decreases the proportion of contamination, and does not alter the performance of Xpert MTB/RIF

Iron homeostasis during anemia of inflammation: a prospective study in patients with tuberculosis.

Anemia of inflammation is a hallmark of tuberculosis. Factors controlling iron metabolism during anemia of inflammation and its resolution are uncertain. Whether iron supplements should be given during anti-tuberculosis treatment to support Hb recovery is unclear. Before and during treatment of tuberculosis, we assessed iron kinetics, and changes in inflammation and iron metabolism indices. In a 26-wk prospective study, Tanzanian adults with tuberculosis (n=18) were studied before treatment and then every two weeks during treatment; oral and intravenous iron tracers were administered before treatment, after intensive phase (8/12 wk) and complete treatment (24 wk); no iron supplements were given. Before treatment, hepcidin and erythroferrone (ERFE) were greatly elevated, erythrocyte iron utilization was high (~80%) and iron absorption was negligible (<1%). During treatment, hepcidin and IL-6 decreased ~70% after only 2 wk (p<0.001); in contrast, ERFE did not significantly decrease until 8 wk (p<0.01). ERFE and IL-6 were the main opposing determinants of hepcidin (p<0.05) and greater ERFE was associated with reticulocytosis and hemoglobin (Hb) repletion (p<0.01). Dilution of baseline tracer concentration was 2.6-fold higher during intensive phase treatment (p<0.01) indicating enhanced erythropoiesis. After treatment completion, iron absorption increased ~20-fold (p<0.001); Hb increased ~25% (p<0.001). In tuberculosis-associated anemia of inflammation, our findings suggest elevated ERFE is unable to suppress hepcidin and iron absorption is negligible. During treatment, as inflammation resolves, ERFE may remain elevated, contributing to hepcidin suppression and Hb repletion. Iron is well-absorbed only after tuberculosis treatment and supplementation should be reserved for patients remaining anemic after treatment. (ClinicalTrials.gov Identifier:NCT02176772)

Prevalence and clinical relevance of helminth co-infections among tuberculosis patients in urban Tanzania

Helminth infections can negatively affect the immunologic host control, which may increase the risk of progression from latent Mycobacterium tuberculosis infection to tuberculosis (TB) disease and alter the clinical presentation of TB. We assessed the prevalence and determined the clinical relevance of helminth co-infection among TB patients and household contact controls in urban Tanzania.; Between November 2013 and October 2015, we enrolled adult (≥18 years) sputum smear-positive TB patients and household contact controls without TB during an ongoing TB cohort study in Dar es Salaam, Tanzania. We used Baermann, FLOTAC, Kato-Katz, point-of-care circulating cathodic antigen, and urine filtration to diagnose helminth infections. Multivariable logistic regression models with and without random effects for households were used to assess for associations between helminth infection and TB.; A total of 597 TB patients and 375 household contact controls were included. The median age was 33 years and 60.2% (585/972) were men. The prevalence of any helminth infection among TB patients was 31.8% (190/597) and 25.9% (97/375) among controls. Strongyloides stercoralis was the predominant helminth species (16.6%, 161), followed by hookworm (9.0%, 87) and Schistosoma mansoni (5.7%, 55). An infection with any helminth was not associated with TB (adjusted odds ratio (aOR) 1.26, 95% confidence interval (CI): 0.88-1.80, p = 0.22), but S. mansoni infection was (aOR 2.15, 95% CI: 1.03-4.45, p = 0.040). Moreover, S. mansoni infection was associated with lower sputum bacterial load (aOR 2.63, 95% CI: 1.38-5.26, p = 0.004) and tended to have fewer lung cavitations (aOR 0.41, 95% CI: 0.12-1.16, p = 0.088).; S. mansoni infection was an independent risk factor for active TB and altered the clinical presentation in TB patients. These findings suggest a role for schistosomiasis in modulating the pathogenesis of human TB. Treatment of helminths should be considered in clinical management of TB and TB control programs

The Sputum Microbiome in Pulmonary Tuberculosis and Its Association With Disease Manifestations: A Cross-Sectional Study.

Each day, approximately 27,000 people become ill with tuberculosis (TB), and 4,000 die from this disease. Pulmonary TB is the main clinical form of TB, and affects the lungs with a considerably heterogeneous manifestation among patients. Immunomodulation by an interplay of host-, environment-, and pathogen-associated factors partially explains such heterogeneity. Microbial communities residing in the host's airways have immunomodulatory effects, but it is unclear if the inter-individual variability of these microbial communities is associated with the heterogeneity of pulmonary TB. Here, we investigated this possibility by characterizing the microbial composition in the sputum of 334 TB patients from Tanzania, and by assessing its association with three aspects of disease manifestations: sputum mycobacterial load, severe clinical findings, and chest x-ray (CXR) findings. Compositional data analysis of taxonomic profiles based on 16S-rRNA gene amplicon sequencing and on whole metagenome shotgun sequencing, and graph-based inference of microbial associations revealed that the airway microbiome of TB patients was shaped by inverse relationships between Streptococcus and two anaerobes: Selenomonas and Fusobacterium. Specifically, the strength of these microbial associations was negatively correlated with Faith's phylogenetic diversity (PD) and with the accumulation of transient genera. Furthermore, low body mass index (BMI) determined the association between abnormal CXRs and community diversity and composition. These associations were mediated by increased abundance of Selenomonas and Fusobacterium, relative to the abundance of Streptococcus, in underweight patients with lung parenchymal infiltrates and in comparison to those with normal chest x-rays. And last, the detection of herpesviruses and anelloviruses in sputum microbial assemblage was linked to co-infection with HIV. Given the anaerobic metabolism of Selenomonas and Fusobacterium, and the hypoxic environment of lung infiltrates, our results suggest that in underweight TB patients, lung tissue remodeling toward anaerobic conditions favors the growth of Selenomonas and Fusobacterium at the expense of Streptococcus. These new insights into the interplay among particular members of the airway microbiome, BMI, and lung parenchymal lesions in TB patients, add a new dimension to the long-known association between low BMI and pulmonary TB. Our results also drive attention to the airways virome in the context of HIV-TB coinfection

Extrapulmonary tuberculosis in HIV-infected patients in rural Tanzania: the prospective Kilombero and Ulanga antiretroviral cohort

In sub-Saharan Africa, diagnosis and management of extrapulmonary tuberculosis (EPTB) in people living with HIV (PLHIV) remains a major challenge. This study aimed to characterize the epidemiology and risk factors for poor outcome of extrapulmonary tuberculosis in people living with HIV (PLHIV) in a rural setting in Tanzania.; We included PLHIV >18 years of age enrolled into the Kilombero and Ulanga antiretroviral cohort (KIULARCO) from 2013 to 2017. We assessed the diagnosis of tuberculosis by integrating prospectively collected clinical and microbiological data. We calculated prevalence- and incidence rates and used Cox regression analysis to evaluate the association of risk factors in extrapulmonary tuberculosis (EPTB) with a combined endpoint of lost to follow-up (LTFU) and death.; We included 3,129 subjects (64.5% female) with a median age of 38 years (interquartile range [IQR] 31-46) and a median CD4+ cell count of 229/μl (IQR 94-421) at baseline. During the median follow-up of 1.25 years (IQR 0.46-2.85), 574 (18.4%) subjects were diagnosed with tuberculosis, whereof 175 (30.5%) had an extrapulmonary manifestation. Microbiological evidence by Acid-Fast-Bacillus stain (AFB-stain) or Xpert® MTB/RIF was present in 178/483 (36.9%) patients with pulmonary and in 28/175 (16.0%) of patients with extrapulmonary manifestations, respectively. Incidence density rates for pulmonary Tuberculosis (PTB and EPTB were 17.9/1000person-years (py) (95% CI 14.2-22.6) and 5.8/1000 py (95% CI 4.0-8.5), respectively. The combined endpoint of death and LTFU was observed in 1058 (33.8%) patients, most frequently in the subgroup of EPTB (47.2%). Patients with EPTB had a higher rate of the composite outcome of death/LTFU after TB diagnosis than with PTB [HR 1.63, (1.14-2.31); p = 0.006]. The adjusted hazard ratios [HR (95% CI)] for death/LTFU in EPTB patients were significantly increased for patients aged >45 years [HR 1.95, (1.15-3.3); p = 0.013], whereas ART use was protective [HR 0.15, (0.08-0.27); p <0.001].; Extrapulmonary tuberculosis was a frequent manifestation in this cohort of PLHIV. The diagnosis of EPTB in the absence of histopathology and mycobacterial culture remains challenging even with availability of Xpert® MTB/RIF. Patients with EPTB had increased rates of mortality and LTFU despite early recognition of the disease after enrollment

Boosting effect of IL-7 in interferon gamma release assays to diagnose Mycobacterium tuberculosis infection

A quarter of the world's population is estimated to be infected with Myobacterium tuberculosis (Mtb). Infection is detected by immune response to M. tuberculosis antigens using either tuberculin skin test (TST) and interferon gamma release (IGRA's), tests which have low sensitivity in immunocompromised. IL-7 is an important cytokine for T-cell function with potential to augment cytokine release in in-vitro assays. This study aimed to determine whether the addition of IL-7 in interferon-gamma release assays (IGRAs) improves its diagnostic performance of Mtb infection.; 44 cases with confirmed TB and 45 household contacts without TB were recruited and 1ml of blood was stimulated in two separate IGRA's tube set: one set of standard Quantiferon TB gold tubes mitogen, TB antigen and TB Nil; one set of customized Quantiferon TB gold tubes with added IL-7. Following IFN-γ and IP-10 release was determined using ELISA.; We found that the addition of IL-7 led to significantly higher release of IFN-γ in individuals with active TB from 4.2IU/ml (IQR 1.4-6.9IU/ml) to 5.1IU/ml (IQR 1.5-8.1IU/ml, p = 0.0057), and we found an indication of a lower release of both IFN-γ and IP-10 in participants with negative tests.; In TB cases addition of IL-7 in IGRA tubes augments IFN-γ but not IP-10 release, and seems to lower the response in controls. Whether IL-7 boosted IGRA holds potential over standard IGRA needs to be confirmed in larger studies in high and low TB incidence countries

Home-Based and Facility-Based Directly Observed Therapy of Tuberculosis Treatment under Programmatic Conditions in Urban Tanzania.

INTRODUCTION Decentralization of Directly Observed Treatment (DOT) for tuberculosis (TB) to the community (home-based DOT) has improved the coverage of TB treatment and reduced the burden to the health care facilities (facility-based DOT). We aimed to compare TB treatment outcomes in home-based and facility-based DOT under programmatic conditions in an urban setting with a high TB burden. METHODOLOGY A retrospective analysis of a cohort of adult TB patients (≥15 years) routinely notified between 2010 and 2013 in two representative TB sub-districts in the Temeke district, Dar es Salaam, Tanzania. We assessed differences in treatment outcomes by calculating Risk Ratios (RRs). We used logistic regression to assess the association between DOT and treatment outcomes. RESULTS Data of 4,835 adult TB patients were analyzed, with a median age of 35 years, 2,943 (60.9%) were men and TB/HIV co-infection prevalence of 39.9%. A total of 3,593 (74.3%) patients were treated under home-based DOT. Patients on home-based DOT were more likely to die compared to patients on facility-based DOT (RR 2.04, 95% Confidence Interval [95% CI]: 1.52-2.73), and more likely to complete TB treatment (RR 1.14, 95% CI: 1.06-1.23), but less likely to have a successful treatment outcome (RR 0.94, 95% CI: 0.92-0.97). Home-based DOT was preferred by women (adjusted Odds Ratio [aOR] 1.55, 95% CI: 1.34-1.80, p<0.001), older people (aOR 1.01 for each year increase, 95% CI: 1.00-1.02, p = 0.001) and patients with extra-pulmonary TB (aOR 1.45, 95% CI: 1.16-1.81, p = 0.001), but less frequently by patients on a retreatment regimen (aOR 0.12, 95% CI: 0.08-0.19, p<0.001). CONCLUSIONS/SIGNIFICANCE TB patients under home-based DOT had more frequently risk factors of death such as older age, HIV infection and sputum smear-negative TB, and had higher mortality compared to patients under facility-based DOT. Further operational research is needed to monitor the implementation of DOT under programmatic conditions