Journal Article

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

Vallely, Andrew, Kelly, Gerard, Henri, Iata, Tatem, Andrew J, Iamaher, Sam, Harris, Ivor, Taleo, George, Clements, Archie CA, Reid, Heidi, Riley, Ian

2010

Overview

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.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Autocorrelation / Bayes Theorem / Bayesian analysis / Biomedical and Life Sciences / Biomedicine / Child / Child, Preschool / Climate change / Consortia / Demographic aspects / Disease transmission / Distance / Distribution / Entomology / Female / Geographic Information Systems / Geostatistics / Health risks / Human diseases / Humans / Infections / Infectious Diseases / Insecticides / Islands / Logistic Models / Malaria / Malaria - epidemiology / Malaria - parasitology / Malaria - prevention & control / Malaria, Falciparum - diagnosis / Malaria, Falciparum - epidemiology / Malaria, Falciparum - parasitology / Male / Microbiology / Parasitology / Plasmodium falciparum / Plasmodium falciparum - isolation & purification / Plasmodium vivax / Plasmodium vivax - isolation & purification / Polymerase Chain Reaction / Prediction models / Prevalence / Prevalence studies (Epidemiology) / Prevention / Probability theory / Public Health / Regression analysis / Risk / Risk factors / Sleep / Software / Spatial distribution / Statistical analysis / Statistical methods / Surveying / Towards malaria elimination / Tropical Medicine / Vanuatu - epidemiology / Vector-borne diseases