Dataset Information

An environmental assessment and risk map of Ascaris lumbricoides and Necator americanus distributions in Manufahi District, Timor-Leste.

ABSTRACT:

Background

In Timor-Leste there have been intermittent and ineffective soil-transmitted helminth (STH) deworming programs since 2004. In a resource-constrained setting, having information on the geographic distribution of STH can aid in prioritising high risk communities for intervention. This study aimed to quantify the environmental risk factors for STH infection and to produce a risk map of STH in Manufahi district, Timor-Leste.

Methodology/principal findings

Georeferenced cross-sectional data and stool samples were obtained from 2,194 participants in 606 households in 24 villages in the Manufahi District as part of cross sectional surveys done in the context of the "WASH for Worms" randomised controlled trial. Infection status was determined for Ascaris lumbricoides and Necator americanus using real-time quantitative polymerase chain reaction. Baseline infection data were linked to environmental data obtained for each household. Univariable and multivariable multilevel mixed-effects logistic regression analysis with random effects at the village and household level were conducted, with all models adjusted for age and sex. For A. lumbricoides, being a school-aged child increased the odds of infection, whilst higher temperatures in the coolest quarter of the year, alkaline soils, clay loam/loam soils and woody savannas around households were associated with decreased infection odds. For N. americanus, greater precipitation in the driest month, higher average enhanced vegetation index, age and sandy loam soils increased infection odds, whereas being female and living at higher elevations decreased the odds of infection. Predictive risk maps generated for Manufahi based upon these final models highlight the high predicted risk of N. americanus infection across the district and the more focal nature of A. lumbricoides infection. The predicted risk of any STH infection is high across the entire district.

Conclusions/significance

The widespread predicted risk of any STH infection in 6 to 18 year olds provides strong evidence to support strategies for control across the entire geographical area. As few studies include soil texture and pH in their analysis, this study adds to a growing body of evidence suggesting these factors influence STH infection distribution. This study also further supports that A. lumbricoides prefers acidic soils, highlighting a potential relatively unexplored avenue for control.

Trial registration

ClinicalTrials.gov ACTRN12614000680662.

SUBMITTER: Wardell R

PROVIDER: S-EPMC5440046 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

An environmental assessment and risk map of Ascaris lumbricoides and Necator americanus distributions in Manufahi District, Timor-Leste.

Wardell Rebecca R Clements Archie C A ACA Lal Aparna A Summers David D Llewellyn Stacey S Campbell Suzy J SJ McCarthy James J Gray Darren J DJ V Nery Susana S

PLoS neglected tropical diseases 20170510 5

<h4>Background</h4>In Timor-Leste there have been intermittent and ineffective soil-transmitted helminth (STH) deworming programs since 2004. In a resource-constrained setting, having information on the geographic distribution of STH can aid in prioritising high risk communities for intervention. This study aimed to quantify the environmental risk factors for STH infection and to produce a risk map of STH in Manufahi district, Timor-Leste.<h4>Methodology/principal findings</h4>Georeferenced cros ...[more]

PMID: 28489889

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Project description:BACKGROUND: The island of Timor lies at the south-eastern edge of Indonesia on the boundary of the Oriental and Australian faunal regions. The country of Timor-Leste, which occupies the eastern part of the island, is malarious, but anopheline faunal surveys and malaria vector incrimination date back to the 1960 s. Over the last decade the malaria vectors of south-east Asia and the south-west Pacific have been intensely studied using molecular techniques that can confirm identification within complexes of isomorphic species. The aim of this study is to accurately identify the Anopheles fauna of Timor-Leste using these techniques. METHODS: The survey was carried out over the period February to June 2001. Standard entomological techniques--human landing collections, larval collections and CO2 baited light traps--were used to collect anophelines from the main geographical regions: coastal plains, inland plains, and highlands. Specimens were processed for identification by morphology and genotyped for the ribosomal DNA ITS2 by restriction analysis and/or DNA sequencing. Phylogenetic relationship of Anopheles sundaicus and Anopheles subpictus individuals was also assessed using DNA sequences from the ITS2 and mitochondrial cytochrome-b. All specimens, other than those from larval surveys, were processed to detect the presence of the Plasmodium parasite circumsporozoite protein by ELISA for vector incrimination. RESULTS: Of 2,030 specimens collected, seven species were identified by morphology: Anopheles barbirostris, Anopheles aconitus, Anopheles annularis, Anopheles maculatus, Anopheles peditaeniatus, An. sundaicus and Anopheles vagus. These were confirmed by molecular analysis with the addition of Anopheles flavirostris and an unidentified species designated here as An. vagus genotype B. This latter species was morphologically similar to An. vagus and An. subpictus and is likely to be the An. subpictus described by other workers for Timor. However, genetically this species showed strong affinities to the An. sundaicus complex. Anopheles vagus was the most common species but was rarely collected coming to bite humans; An. barbirostris and An. vagus genotype B were the two most common species collected in human landing catches and both were found positive for CS protein. CONCLUSIONS: The anopheline fauna of Timor-Leste is of Oriental origin with no evidence of elements from the Australian Region. The existence of species complexes will make the use of morphological markers problematic in the country. Using molecular analysis a number of issues regarding the anopheline fauna of Timor-Leste were resolved and nine putative species of Anopheles were identified; two species: An. barbirostris and An. vagus genotype B, were incriminated as malaria vectors.

Project description:Fieldwork conducted throughout Timor-Leste in September 2004 and July 2009 resulted in a collection or recording of 263 herpetological specimens (100 amphibians, 163 reptiles), comprising at least seven species of frogs and toads, 20 species of lizards, seven species of snakes, two species of turtles, and one species of crocodile. Among the amphibians, the most frequently encountered species were toads (Duttaphrynus melanostictus), rice paddy frogs (genus Fejervarya), and rhacophorid treefrogs (Polypedates cf. leucomystax). All three variants of rice paddy frogs encountered represent undescribed species similar to Fejervarya verruculosa from neighboring Wetar Island. Records of Fejervarya cancrivora and Fejervarya limnocharis for Timor Island are apparently errors based on misidentification. We obtained voucher specimens for a total of 147 lizards and voucher photographs only for four specimens of Varanus timorensis. Aside from geckos frequently associated with human habitations (e.g., Gehyra mutilata, Gekko gecko, Hemidactylus frenatus, Hemidactylus platyurus), we discovered an as yet undescribed species of bent-toed gecko, genus Cyrtodactylus, in the Same valley. Our specimens of Hemidactylus platyurus are the first record of this species from Timor-Leste. Commonly encountered skinks included four-fingered skinks (genus Carlia), wedge skinks (genus Sphenomorphus), and night skinks (genus Eremiascincus). Notable among the 15 snakes collected was the frequency of pitvipers (Cryptelytrops insularis), which amounted to over 25% of all snakes. Our specimen of the wolfsnake Lycodon subcinctus is the first record of this species for Timor-Leste. Based on these findings, it appears that the biodiversity of amphibians and reptiles in this remote corner of Wallacea is much greater than previously thought, particularly with respect to scincid lizards. The detail we provide in the species accounts is designed to allow the use of this report as a preliminary field guide to the amphibians and reptiles of Timor-Leste. However, survey work is ongoing.

Dataset Information

An environmental assessment and risk map of Ascaris lumbricoides and Necator americanus distributions in Manufahi District, Timor-Leste.

Background

Methodology/principal findings

Conclusions/significance

Trial registration

Publications

An environmental assessment and risk map of Ascaris lumbricoides and Necator americanus distributions in Manufahi District, Timor-Leste.

Similar Datasets

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