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The dispersal ecology of Rhodesian sleeping sickness following its introduction to a new area.

ABSTRACT: Tsetse-transmitted human and animal trypanosomiasis are constraints to both human and animal health in sub-Saharan Africa, and although these diseases have been known for over a century, there is little recent evidence demonstrating how the parasites circulate in natural hosts and ecosystems. The spread of Rhodesian sleeping sickness (caused by Trypanosoma brucei rhodesiense) within Uganda over the past 15 years has been linked to the movement of infected, untreated livestock (the predominant reservoir) from endemic areas. However, despite an understanding of the environmental dependencies of sleeping sickness, little research has focused on the environmental factors controlling transmission establishment or the spatially heterogeneous dispersal of disease following a new introduction. In the current study, an annually stratified case-control study of Rhodesian sleeping sickness cases from Serere District, Uganda was used to allow the temporal assessment of correlations between the spatial distribution of sleeping sickness and landscape factors. Significant relationships were detected between Rhodesian sleeping sickness and selected factors, including elevation and the proportion of land which was "seasonally flooding grassland" or "woodlands and dense savannah." Temporal trends in these relationships were detected, illustrating the dispersal of Rhodesian sleeping sickness into more 'suitable' areas over time, with diminishing dependence on the point of introduction in concurrence with an increasing dependence on environmental and landscape factors. These results provide a novel insight into the ecology of Rhodesian sleeping sickness dispersal and may contribute towards the implementation of evidence-based control measures to prevent its further spread.

SUBMITTER: Wardrop NA

PROVIDER: S-EPMC3794918 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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The dispersal ecology of Rhodesian sleeping sickness following its introduction to a new area.

Wardrop Nicola A NA Fèvre Eric M EM Atkinson Peter M PM Welburn Susan C SC

PLoS neglected tropical diseases 20131010 10

Tsetse-transmitted human and animal trypanosomiasis are constraints to both human and animal health in sub-Saharan Africa, and although these diseases have been known for over a century, there is little recent evidence demonstrating how the parasites circulate in natural hosts and ecosystems. The spread of Rhodesian sleeping sickness (caused by Trypanosoma brucei rhodesiense) within Uganda over the past 15 years has been linked to the movement of infected, untreated livestock (the predominant re ...[more]

PMID: 24130913

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Project description:The number of imported Human African Trypanosomiasis (HAT) cases in non-endemic countries has increased over the last years. The objective of this analysis is to describe the clinical presentation of HAT in Caucasian travelers. Literature was screened (MEDLINE, Pubmed) using the terms "Human African Trypanosomiasis", "travelers" and "expatriates"; all European languages except Slavic ones were included. Publications without clinical description of patients were only included in the epidemiological analysis. Forty-five reports on Caucasians with T.b. rhodesiense and 15 with T.b. gambiense infections were included in the analysis of the clinical parameters. Both species have presented with fever (T.b. rhodesiense 97.8% and T.b. gambiense 93.3%), headache (50% each) and a trypanosomal chancre (T.b. rhodesiense 84.4%, T.b. gambiense 46.7%). While sleeping disorders dominate the clinical presentation of HAT in endemic regions, there have been only rare reports in travelers: insomnia (T.b. rhodesiense 7.1%, T.b. gambiense 21.4%), diurnal somnolence (T.b. rhodesiense 4.8%, T.b. gambiense none). Surprisingly, jaundice has been seen in 24.2% of the Caucasian T.b. rhodesiense patients, but has never been described in HAT patients in endemic regions. These results contrast to the clinical presentation of T.b. gambiense and T.b. rhodesiense HAT in Africans in endemic regions, where the presentation of chronic T.b. gambiense and acute T.b. rhodesiense HAT is different. The analysis of 14 reports on T.b. gambiense HAT in Africans living in a non-endemic country shows that neurological symptoms such as somnolence (46.2%), motor deficit (64.3%) and reflex anomalies (14.3%) as well as psychiatric symptoms such as hallucinations (21.4%) or depression (21.4%) may dominate the clinical picture. Often, the diagnosis has been missed initially: some patients have even been hospitalized in psychiatric clinics. In travelers T.b. rhodesiense and gambiense present as acute illnesses and chancres are frequently seen. The diagnosis of HAT in Africans living outside the endemic region is often missed or delayed, leading to presentation with advanced stages of the disease.

Project description:BackgroundHuman African trypanosomiasis (HAT), also known as sleeping sickness, is a fatal parasitic disease caused by trypanosomes. Current treatment options for HAT are scarce, toxic, no longer effective, or very difficult to administer, in particular for the advanced, fatal stage of the disease (stage 2, chronic HAT). New safe, effective and easy-to-use treatments are urgently needed. Here it is shown that fexinidazole, a 2-substituted 5-nitroimidazole rediscovered by the Drugs for Neglected Diseases initiative (DNDi) after extensive compound mining efforts of more than 700 new and existing nitroheterocycles, could be a short-course, safe and effective oral treatment curing both acute and chronic HAT and that could be implemented at the primary health care level. To complete the preclinical development and meet the regulatory requirements before initiating human trials, the anti-parasitic properties and the pharmacokinetic, metabolic and toxicological profile of fexinidazole have been assessed.Methods and findingsStandard in vitro and in vivo anti-parasitic activity assays were conducted to assess drug efficacy in experimental models for HAT. In parallel, a full range of preclinical pharmacology and safety studies, as required by international regulatory guidelines before initiating human studies, have been conducted. Fexinidazole is moderately active in vitro against African trypanosomes (IC?? against laboratory strains and recent clinical isolates ranged between 0.16 and 0.93 µg/mL) and oral administration of fexinidazole at doses of 100 mg/kg/day for 4 days or 200 mg/kg/day for 5 days cured mice with acute and chronic infection respectively, the latter being a model for the advanced and fatal stage of the disease when parasites have disseminated into the brain. In laboratory animals, fexinidazole is well absorbed after oral administration and readily distributes throughout the body, including the brain. The absolute bioavailability of oral fexinidazole was 41% in mice, 30% in rats, and 10% in dogs. Furthermore, fexinidazole is rapidly metabolised in vivo to at least two biologically active metabolites (a sulfoxide and a sulfone derivative) that likely account for a significant portion of the therapeutic effect. Key pharmacokinetic parameter after oral absorption in mice for fexinidazole and its sulfoxide and sulfone metabolites are a C(max) of 500, 14171 and 13651 ng/mL respectively, and an AUC???? of 424, 45031 and 96286 h.ng/mL respectively. Essentially similar PK profiles were observed in rats and dogs. Toxicology studies (including safety pharmacology and 4-weeks repeated-dose toxicokinetics in rat and dog) have shown that fexinidazole is well tolerated. The No Observed Adverse Event Levels in the 4-weeks repeated dose toxicity studies in rats and dogs was 200 mg/kg/day in both species, with no issues of concern identified for doses up to 800 mg/kg/day. While fexinidazole, like many nitroheterocycles, is mutagenic in the Ames test due to bacterial specific metabolism, it is not genotoxic to mammalian cells in vitro or in vivo as assessed in an in vitro micronucleus test on human lymphocytes, an in vivo mouse bone marrow micronucleus test, and an ex vivo unscheduled DNA synthesis test in rats.ConclusionsThe results of the preclinical pharmacological and safety studies indicate that fexinidazole is a safe and effective oral drug candidate with no untoward effects that would preclude evaluation in man. The drug has entered first-in-human phase I studies in September 2009. Fexinidazole is the first new clinical drug candidate with the potential for treating advanced-stage sleeping sickness in thirty years.

Dataset Information

The dispersal ecology of Rhodesian sleeping sickness following its introduction to a new area.

Publications

The dispersal ecology of Rhodesian sleeping sickness following its introduction to a new area.

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