Abstract
Background
Bhutan has achieved a substantial reduction in both malaria morbidity and mortality over the last two decades and is aiming for malaria elimination certification in 2025. However, a sig-nificant percentage of malaria cases in Bhutan are imported (acquired in another country). The aim of the study was to understand how importation drives local malaria transmission in Bhu-tan.
Methods
Information on geo-located individual-level laboratory-confirmed malaria cases between 2016 and 2020 was obtained from the Bhutan Vector-borne Disease Control Program. Records in-cluded the date of diagnosis and treatment, type of cases classified as indigenous or import-ed, and malaria species. Hawkes Processes were used to study the role of imported malaria in local transmission in Bhutan. We imposed 15 days delay for a mosquito to become infectious in the model.
Findings
There were 285 cases during the study period and 58·6% (159) were imported malaria. 71·1% (113) of these imported cases were Plasmodium vivax and 73·6% (117) were from India. The model suggested that a person remains infectious for 8 days for Plasmodium falciparum ma-laria but over 19 days for Plasmodium vivax. The background intensity from imported malaria cases was much greater for P. vivax cases (maximum 0·17) resulting in more importations than P. falciparum cases (maximum 0·06). However, model fitting suggested that local P. falcipa-rum transmission was mainly driven by importations but additional factors such as relapse played a role for P. vivax.
Interpretation
Imported malaria cases are key drivers of transmission within Bhutan, with most cases since 2016 being P. vivax. Control programmes should be devised to target interventions towards the P. vivax strain and test those who are more likely to bring in imported malaria cases or ac-quire it from returning travellers.
Bhutan has achieved a substantial reduction in both malaria morbidity and mortality over the last two decades and is aiming for malaria elimination certification in 2025. However, a sig-nificant percentage of malaria cases in Bhutan are imported (acquired in another country). The aim of the study was to understand how importation drives local malaria transmission in Bhu-tan.
Methods
Information on geo-located individual-level laboratory-confirmed malaria cases between 2016 and 2020 was obtained from the Bhutan Vector-borne Disease Control Program. Records in-cluded the date of diagnosis and treatment, type of cases classified as indigenous or import-ed, and malaria species. Hawkes Processes were used to study the role of imported malaria in local transmission in Bhutan. We imposed 15 days delay for a mosquito to become infectious in the model.
Findings
There were 285 cases during the study period and 58·6% (159) were imported malaria. 71·1% (113) of these imported cases were Plasmodium vivax and 73·6% (117) were from India. The model suggested that a person remains infectious for 8 days for Plasmodium falciparum ma-laria but over 19 days for Plasmodium vivax. The background intensity from imported malaria cases was much greater for P. vivax cases (maximum 0·17) resulting in more importations than P. falciparum cases (maximum 0·06). However, model fitting suggested that local P. falcipa-rum transmission was mainly driven by importations but additional factors such as relapse played a role for P. vivax.
Interpretation
Imported malaria cases are key drivers of transmission within Bhutan, with most cases since 2016 being P. vivax. Control programmes should be devised to target interventions towards the P. vivax strain and test those who are more likely to bring in imported malaria cases or ac-quire it from returning travellers.
| Original language | English |
|---|---|
| Article number | 100497 |
| Number of pages | 10 |
| Journal | The Lancet Regional Health - Southeast Asia |
| Volume | 31 |
| Early online date | 16 Oct 2024 |
| DOIs | |
| Publication status | Published - 1 Dec 2024 |
Bibliographical note
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