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Baseline spatial distribution of malaria prior to an elimination programme in Vanuatu

Baseline spatial distribution of malaria prior to an elimination programme in Vanuatu
Baseline spatial distribution of malaria prior to an elimination programme in Vanuatu
BACKGROUND: The Ministry of Health in the Republic of Vanuatu has implemented a malaria elimination programme in Tafea Province, the most southern and eastern limit of malaria transmission in the South West Pacific. Tafea Province is comprised of five islands with malaria elimination achieved on one of these islands (Aneityum) in 1998. The current study aimed to establish the baseline distribution of malaria on the most malarious of the province's islands, Tanna Island, to guide the implementation of elimination activities. METHODS: A parasitological survey was conducted in Tafea Province in 2008. On Tanna Island there were 4,716 participants from 220 villages, geo-referenced using a global position system. Spatial autocorrelation in observed prevalence values was assessed using a semivariogram. Backwards step-wise regression analysis was conducted to determine the inclusion of environmental and climatic variables into a prediction model. The Bayesian geostatistical logistic regression model was used to predict malaria risk, and associated uncertainty across the island. RESULTS: Overall, prevalence on Tanna was 1.0% for Plasmodium falciparum (accounting for 32% of infections) and 2.2% for Plasmodium vivax (accounting for 68% of infections). Regression analysis showed significant association with elevation and distance to coastline for P. vivax and P. falciparum, but no significant association with NDVI or TIR. Colinearity was observed between elevation and distance to coastline with the later variable included in the final Bayesian geostatistical model for P. vivax and the former included in the final model for P. falciparum. Model validation statistics revealed that the final Bayesian geostatistical model had good predictive ability. CONCLUSION: Malaria in Tanna Island, Vanuatu, has a focal and predominantly coastal distribution. As Vanuatu refines its elimination strategy, malaria risk maps represent an invaluable resource in the strategic planning of all levels of malaria interventions for the island.
bayes theorem, child, preschool female, geographic information systems, humans, logistic models, malaria, epidemiology, parasitology, prevention & control, falciparum, diagnosis, epidemiology parasitology, maleplasmodium falciparum, isolation & purification, plasmodium vivax, polymerase chain reactionprevalence, risk, vanuatu
1475-2875
150-[9pp]
Reid, H.
4f221910-f3f2-41bc-ab4b-66ab4b88744f
Vallely, A.
46020b1f-b530-470a-981f-660f3c7462a7
Taleo, G.
54242f45-704e-4c1d-baf0-bbd570217bb2
Tatem, A.J.
6c6de104-a5f9-46e0-bb93-a1a7c980513e
Kelly, G.
4ec853ad-85b1-40c5-8537-2f6f83d852c2
Riley, I.
eaf41755-d4fd-425c-8029-4cc338d55c9e
Harris, I.
ea4d0481-d1d0-45b5-998f-173224560d9b
Henri, I.
60004c71-fddd-4aa3-8d96-9a29e59283fa
Iamaher, S.
c6e1616c-da37-44ae-8fec-283d5216f575
Clements, A.C.
26bb7239-e58c-4f3e-a5ce-97817fb85962
Reid, H.
4f221910-f3f2-41bc-ab4b-66ab4b88744f
Vallely, A.
46020b1f-b530-470a-981f-660f3c7462a7
Taleo, G.
54242f45-704e-4c1d-baf0-bbd570217bb2
Tatem, A.J.
6c6de104-a5f9-46e0-bb93-a1a7c980513e
Kelly, G.
4ec853ad-85b1-40c5-8537-2f6f83d852c2
Riley, I.
eaf41755-d4fd-425c-8029-4cc338d55c9e
Harris, I.
ea4d0481-d1d0-45b5-998f-173224560d9b
Henri, I.
60004c71-fddd-4aa3-8d96-9a29e59283fa
Iamaher, S.
c6e1616c-da37-44ae-8fec-283d5216f575
Clements, A.C.
26bb7239-e58c-4f3e-a5ce-97817fb85962

Reid, H., Vallely, A., Taleo, G., Tatem, A.J., Kelly, G., Riley, I., Harris, I., Henri, I., Iamaher, S. and Clements, A.C. (2010) Baseline spatial distribution of malaria prior to an elimination programme in Vanuatu. Malaria Journal, 9, 150-[9pp]. (doi:10.1186/1475-2875-9-150). (PMID:20525209)

Record type: Article

Abstract

BACKGROUND: The Ministry of Health in the Republic of Vanuatu has implemented a malaria elimination programme in Tafea Province, the most southern and eastern limit of malaria transmission in the South West Pacific. Tafea Province is comprised of five islands with malaria elimination achieved on one of these islands (Aneityum) in 1998. The current study aimed to establish the baseline distribution of malaria on the most malarious of the province's islands, Tanna Island, to guide the implementation of elimination activities. METHODS: A parasitological survey was conducted in Tafea Province in 2008. On Tanna Island there were 4,716 participants from 220 villages, geo-referenced using a global position system. Spatial autocorrelation in observed prevalence values was assessed using a semivariogram. Backwards step-wise regression analysis was conducted to determine the inclusion of environmental and climatic variables into a prediction model. The Bayesian geostatistical logistic regression model was used to predict malaria risk, and associated uncertainty across the island. RESULTS: Overall, prevalence on Tanna was 1.0% for Plasmodium falciparum (accounting for 32% of infections) and 2.2% for Plasmodium vivax (accounting for 68% of infections). Regression analysis showed significant association with elevation and distance to coastline for P. vivax and P. falciparum, but no significant association with NDVI or TIR. Colinearity was observed between elevation and distance to coastline with the later variable included in the final Bayesian geostatistical model for P. vivax and the former included in the final model for P. falciparum. Model validation statistics revealed that the final Bayesian geostatistical model had good predictive ability. CONCLUSION: Malaria in Tanna Island, Vanuatu, has a focal and predominantly coastal distribution. As Vanuatu refines its elimination strategy, malaria risk maps represent an invaluable resource in the strategic planning of all levels of malaria interventions for the island.

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More information

Published date: June 2010
Keywords: bayes theorem, child, preschool female, geographic information systems, humans, logistic models, malaria, epidemiology, parasitology, prevention & control, falciparum, diagnosis, epidemiology parasitology, maleplasmodium falciparum, isolation & purification, plasmodium vivax, polymerase chain reactionprevalence, risk, vanuatu
Organisations: Geography & Environment, PHEW – P (Population Health)

Identifiers

Local EPrints ID: 344446
URI: https://eprints.soton.ac.uk/id/eprint/344446
ISSN: 1475-2875
PURE UUID: 41b333b1-ac96-4a8f-a334-cf0de99101ed
ORCID for A.J. Tatem: ORCID iD orcid.org/0000-0002-7270-941X

Catalogue record

Date deposited: 05 Nov 2012 11:19
Last modified: 26 Nov 2019 01:37

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