Spatiotemporal epidemiology of indigenous and imported malaria cases in Goa, western India.

Abstract

Background: The state of Goa in western India is world-renowned for its coastline and attracts millions of tourists across the world. Historically, Goa was among the malaria-endemic states in India, with Plasmodium vivax contributing to the majority of the cases. Past malaria outbreaks in Goa have been linked to construction activities, and imported malaria cases threaten malaria elimination efforts in the state.

Methods: The malaria data from the National Centre for Vector Borne Disease Control (NCVBDC) and the Directorate of Health Services, Goa was used to study the spatiotemporal dynamics of Plasmodium falciparum, P. vivax, and mixed infection in Goa from 2000-2023. The spatiotemporal distribution of indigenous and imported malaria cases from 2014-2023 in the different primary/urban/community health centres (PHC/UHC/CHCs) of Goa was analysed using GIS. The spatiotemporal changes of the last three decades in Goa's land use/land cover (LU/LC) were assessed using Landsat satellite images, and its effect on malaria distribution was analysed.

Results: Over the study period (2000-2023), P. vivax contributed to 78.2% of the caseload. The malaria trend fluctuated from 2000 to 2008, with a steep decline observed from 2009 onwards, and in 2023, zero indigenous cases were reported. The six health centres of Candolim, Margao, Siolim, Vasco, Mapusa, and Panaji reported 57.8% of the total indigenous and imported malaria cases in Goa during 2014-2023. With 292 cases in 2023, the Porvorim UHC has emerged as a new hotspot of imported malaria cases. The LU/LC change analysis shows a four-fold increase of built-up area, from ~ 70 sq. km in 1991 to 260 sq. km in 2024, with strong spatial overlap between new built-up areas and malaria cases.

Conclusion: Due to the concerted parasite and vector control strategies of the state health department, Goa has achieved the target of zero indigenous malaria cases in 2023. Despite achieving this milestone, the threat of imported malaria cases leading to local outbreaks remains a serious concern.