Distinct clinical characteristics and helminth co-infections in adult tuberculosis patients from urban compared to rural Tanzania

Abstract

Background: Differences in rural and urban settings could account for distinct characteristics in the epidemiology of tuberculosis (TB). We comparatively studied epidemiological features of TB and helminth co-infections in adult patients from rural and urban settings of Tanzania. Methods: Adult patients (≥ 18 years) with microbiologically confirmed pulmonary TB were consecutively enrolled into two cohorts in Dar es Salaam, with ~4.4 million inhabitants (urban), and Ifakara in the sparsely populated Kilombero District with ~400000 inhabitants (rural). Clinical data were obtained at recruitment. Stool and urine samples were subjected to diagnose helminthiases using Kato-Katz, Baermann, urine filtration, and circulating cathodic antigen tests. Differences between groups were assessed by χ 2, Fisher's exact, and Wilcoxon rank sum tests. Logistic regression models were used to determine associations. Results: Between August 2015 and February 2017, 668 patients were enrolled, 460 (68.9%) at the urban and 208 (31.1%) at the rural site. Median patient age was 35 years (interquartile range [IQR]: 27-41.5 years), and 454 (68%) were males. 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), and in HIV/TB co-infected patients a lower median CD4 cell counts (147 cells/μl vs. 249 cells/μl, P=0.02) compared to those from urban Tanzania. There was no significant difference in frequencies of HIV infection, diabetes mellitus, and haemoglobin concentration levels between the two settings. The overall prevalence of helminth co-infections was 22.9% (95% confidence interval [CI]: 20.4-27.0%). The significantly higher prevalence of helminth infections at the urban site (25.7% vs. 17.3%, P=0.018) was predominantly driven by Strongyloides stercoralis (17.0% vs. 4.8%, P< 0.001) and Schistosoma mansoni infection (4.1% vs. 16.4%, P< 0.001). 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). Conclusions: Clinical characteristics and helminth co-infections pattern differ in TB patients in urban and rural Tanzania. The differences underline the need for setting-specific, tailored public health interventions to improve clinical management of TB and comorbidities.