A foci cohort analysis to monitor successful and persistent foci under Thailand’s Malaria Elimination Strategy

Abstract

Background Thailand’s success in reducing malaria burden is built on the efficient “1-3-7” strategy applied to the surveillance system. The strategy is based on rapid case notification within 1 day, case investigation within 3 days, and targeted foci response to reduce the spread of Plasmodium spp. within 7 days. Autochthonous transmission is still occurring in the country, threatening the goal of reaching malaria-free status by 2024. This study aimed to assess the effectiveness of the 1-3-7 strategy and identify factors associated with presence of active foci. Methods Data from the national malaria information system were extracted from fiscal years 2013 to 2019; after data cleaning, the final dataset included 81,012 foci. A Cox’s proportional hazards model was built to investigate factors linked with the probability of becoming an active focus from 2015 to 2019 among foci that changed status from non-active to active focus during the study period. We performed a model selection technique based on the Akaike Information Criteria (AIC). Results The number of yearly active foci decreased from 2227 to 2013 to 700 in 2019 (68.5 %), and the number of autochthonous cases declined from 17,553 to 3,787 (78.4 %). The best Cox’s hazard model showed that foci in which vector control interventions were required were 18 % more likely to become an active focus. Increasing compliance with the 1-3-7 strategy had a protective effect, with a 22 % risk reduction among foci with over 80 % adherence to 1-3-7 timeliness protocols. Other factors associated with likelihood to become or remain an active focus include previous classification as an active focus, presence of Plasmodium falciparum infections, level of forest disturbance, and location in border provinces. Conclusions These results identified factors that favored regression of non-active foci to active foci during the study period. The model and relative risk map align with the national malaria program’s district stratification and shows strong spatial heterogeneity, with high probability to record active foci in border provinces. The results of the study may be useful for honing Thailand’s program to eliminate malaria and for other countries aiming to accelerate malaria elimination.

Progress and challenges of integrated drug efficacy surveillance for uncomplicated malaria in Thailand

“…Thailand has made significant progress towards malaria elimination, surpassing its 2020 milestone reductions for both malaria incidence and mortality [ 8 ]. However, many areas remain receptive to malaria, and re-establishment of transmission continues to be a significant risk across most of the country [ 26 ].…”

Civilian-military malaria outbreak response in Thailand: an example of multi-stakeholder engagement for malaria elimination

“…These could include the chemoprophylaxis strategies (e.g., individual chemoprevention, focal mass drug administration); spatial repellents; wearing long-sleeve shirts, trousers, and socks; insecticide-treated clothing; and/or alternative ways for high-risk populations to access prevention and treatment services (e.g., via peer navigators or mobile malaria workers that can test and treat in forest fringe areas during the high malaria season) [ 26 , 27 ]. In addition, improving upon prompt case management and timeliness of “1–3–7” activities, particularly in border and forested areas, would help to predict and mitigate future outbreaks [ 28 ].…”

Assessing Thailand’s 1-3-7 surveillance strategy in accelerating malaria elimination

“…Any focus that has recorded an indigenous case in the previous three years (based on an annual focus classi cation cycle) is considered to be an "active focus" (22). It is worth noting that the number of active foci has decreased dramatically, from 2,227 in FY 2013 to 700 in FY 2019, as reported in Sudathip et al, and has further dropped to 469 in FY 2021 (22,23).…”