Research Article: Historical Perspective and Risk of Multiple Neglected Tropical Diseases in Coastal Tanzania: Compositional and Contextual Determinants of Disease Risk

Date Published: August 4, 2015

Publisher: Public Library of Science

Author(s): Frederick Ato Armah, Reginald Quansah, Isaac Luginaah, Ratana Chuenpagdee, Herbert Hambati, Gwyn Campbell, Giovanna Raso.

Abstract: BackgroundIn the past decade, research on neglected tropical diseases (NTDs) has intensified in response to the need to enhance community participation in health delivery, establish monitoring and surveillance systems, and integrate existing disease-specific treatment programs to control overlapping NTD burdens and detrimental effects. In this paper, we evaluated the geographical distribution of NTDs in coastal Tanzania.Methods and FindingsWe also assessed the collective (compositional and contextual) factors that currently determine risks to multiple NTDs using a cross sectional survey of 1253 individuals in coastal Tanzania. The results show that the effect size in decreasing order of magnitude for non-binary predictors of NTD risks is as follows: NTD comorbidities > poverty > educational attainment > self-reported household quality of life > ethnicity. The multivariate analysis explained 95% of the variance in the relationship between NTD risks and the theoretically-relevant covariates. Compositional (biosocial and sociocultural) factors explained more variance at the neighbourhood level than at the regional level, whereas contextual factors, such as access to health services and household quality, in districts explained a large proportion of variance at the regional level but individually had modest statistical significance, demonstrating the complex interactions between compositional and contextual factors in generating NTD risks.ConclusionsNTD risks were inequitably distributed over geographic space, which has several important policy implications. First, it suggests that localities of high burden of NTDs are likely to diminish within statistical averages at higher (regional or national) levels. Second, it indicates that curative or preventive interventions will become more efficient provided they can be focused on the localities, particularly as populations in these localities are likely to be burdened by several NTDs simultaneously, further increasing the imperative of multi-disease interventions.

Partial Text: Neglected tropical diseases (NTDs)—a group of seventeen core debilitating infectious diseases [1] that mutually reinforce (act as both a cause and effect of) poverty—have increasingly been receiving cumulative policy, public health attention globally. Neglected tropical diseases affect more than 1 billion people [2, 3] predominantly poor populations living in tropical and subtropical climates. NTDs are endemic in 149 countries with differing populations, economies, resources, political and legal arrangements, health regulations, traditions, cultures, climates, infrastructure and geographies [4]. Yet, NTDs frequently cluster together geographically and individuals are often simultaneously afflicted with more than one parasite or infection (comorbidities). We are still in the early stages of appreciating the full extent of the comorbidity that occurs when the neglected tropical diseases are superimposed on the “Big Three” (HIV/AIDS, tuberculosis, and malaria). Integrated approaches are useful in addressing both NTDs and their comorbidities. For instance, lymphatic filariasis and malaria (NTD comorbidity) are both transmitted by mosquitoes thus distribution of bed nets leads to a decline in both diseases. The pathogens of NTDs have exceedingly complex life-cycles, population dynamics, infection processes and epidemiologies, causing diverse diseases and pathologies [1]. Although they are biomedically heterogeneous, the commonality of NTDs is evidenced in their persistence and prevalence in people and communities living in poverty and social exclusion. It is estimated that more than 70% of countries and territories that report the presence of neglected tropical diseases are low-income or lower middle-income economies especially in sub-Saharan Africa [4]. In particular, those living in remote areas are most vulnerable to infections, and their biological and sociocultural consequences [5]. Notwithstanding this, even within low income countries, there are age- and sex-specific differentials in the health outcomes induced by NTDs. For instance, many NTDs disproportionately affect women and children in sub-Saharan Africa [2, 6].

In this paper, we present a historical overview on the distribution of NTDs in Tanzania during the last two centuries. We also examined the effect sizes of the compositional and contextual determinants of NTD risks with emphasis on coastal Tanzania.



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