Tejedor‐Garavito et al. Malar J (2017) 16:359 DOI 10.1186/s12936-017-2004-8 Malaria Journal RESEARCH Open Access Travel patterns and demographic characteristics of malaria cases in Swaziland, 2010–2014 Natalia Tejedor‐Garavito1*† , Nomcebo Dlamini2†, Deepa Pindolia4, Adam Soble4, Nick W. Ruktanonchai1,3, Victor Alegana1,3, Arnaud Le Menach4, Nyasatu Ntshalintshali4, Bongani Dlamini4, David L. Smith5, Andrew J. Tatem1,3 and Simon Kunene2 Abstract Background: As Swaziland progresses towards national malaria elimination, the importation of parasites into recep- tive areas becomes increasingly important. Imported infections have the potential to instigate local transmission and sustain local parasite reservoirs. Methods: Travel histories from Swaziland’s routine surveillance data from January 2010 to June 2014 were extracted and analysed. The travel patterns and demographics of rapid diagnostic test (RDT)-confrmed positive cases identi- fed through passive and reactive case detection (RACD) were analysed and compared to those found to be negative through RACD. Results: Of 1517 confrmed cases identifed through passive surveillance, 67% reported travel history. A large propor- tion of positive cases reported domestic or international travel history (65%) compared to negative cases (10%). The primary risk factor for malaria infection in Swaziland was shown to be travel, more specifcally international travel to Mozambique by 25- to 44-year old males, who spent on average 28 nights away. Maputo City, Inhambane and Gaza districts were the most likely travel destinations in Mozambique, and 96% of RDT-positive international travellers were either Swazi (52%) or Mozambican (44%) nationals, with Swazis being more likely to test negative. All international travellers were unlikely to have a bed net at home or use protection of any type while travelling. Additionally, paths of transmission, important border crossings and means of transport were identifed. Conclusion: Results from this analysis can be used to direct national and well as cross-border targeting of interven- tions, over space, time and by sub-population. The results also highlight that collaboration between neighbouring countries is needed to tackle the importation of malaria at the regional level. Keywords: Imported malaria, Travel history, Malaria elimination, Reactive case detection, Surveillance system Background risk of acquiring malaria reduced by 37% since 2000 and Global malaria eradication is back on the international the risk of dying from the disease decreasing by 60% [6]. agenda [1, 2], with many countries making malaria elimi- Achieving elimination requires a re-orientation from nation a national goal [3]. Te past decade has seen sig- the universal prevention and treatment measures that nifcant declines in malaria prevalence [4, 5], with the typically defne a control or surveillance programme towards targeted operations, such as identifying residual transmission foci, identifying and curing both asympto- matic and symptomatic infections, focusing vector con- *Correspondence: [email protected] † trol or parasite-based attack measures to high-risk areas Natalia Tejedor‐Garavito and Nomcebo Dlamini are joint frst authors 1 WorldPop, University of Southampton, Southampton, UK and managing importation risk. Understanding human Full list of author information is available at the end of the article movement, which can provide connections between © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Tejedor‐Garavito et al. Malar J (2017) 16:359 Page 2 of 18 disparate high transmission or receptive areas [7], is patient’s home within 7 days (January 2010 to June 2013) important for designing appropriate elimination strate- or 48 h (July 2013 to June 2014) of the patient’s presenta- gies and avoiding resurgence in post-elimination set- tion date, subject to consent by the patient or guardian. tings [8, 9]. Additionally, the identifcation of the sources If the confrmed malaria case lives in Swaziland’s recep- of imported infections play a crucial role in malaria tive area (approximately the eastern half of the coun- programme pre-elimination and elimination phases, try), every person residing within a radius of either 1 km through the assessment of patient travel history records (January 2010 to June 2013) or 500 m (July 2013 to June [10], which makes possible the identifcation of imported 2014) from the residence of the index case is tested for cases and rates, importation routes and the delimitation malaria. A RACD event remains open for up to 5 weeks, of areas with high-risk travellers and sources [8, 9, 11]. where the NMCP additionally conducts fever screening Swaziland is a small, landlocked country in southern and where individuals near the index case report a recent Africa, and due to elevation and climatic conditions the fever, enabling identifcation of any additional malaria majority of Swaziland has historically had low levels of cases (‘secondary cases’). Any identifed positive case is malaria transmission [12]. Te scale-up of interventions referred (often driven) to the nearest health facility for and the expansion of surveillance in recent years, incor- treatment and followed up [19]. Figure 1 outlines the sur- porating active, reactive and proactive case detection, veillance structure. have brought the country close to elimination [12–15]. During both index case investigation and RACD, the Between 2000 and 2014 Swaziland reported a decrease of surveillance agent is required to question each partici- more than 97% in malaria cases and a reduction of over pant on their age, gender, occupation, and nationality. 93% in malaria deaths between 2001 and 2014 [6]. How- Additionally, travel history is recorded, including places ever, population movements, both within and outside the visited during the 8 weeks prior to the investigation, country, especially to malaria-endemic areas, are a hin- duration of stay, reason for travel, means of transport, drance to elimination success [16, 17]. Understanding border crossing sites, and access to/utilization of vector the levels of malaria importation, the sources and routes control and personal protection measures. Te latitude taken by infected travellers, and the characteristics of and longitude of the residence of each individual is also infected travellers compared to those who are uninfected recorded. Once the case investigation is undertaken, is valuable for guiding elimination strategies and design- a case review is carried out to identify the origin of the ing interventions to achieve and sustain malaria elimina- infection and classify cases into the following groups: (1) tion [7, 18]. imported: a case for which the origin can be traced to a Tis article describes the characteristics of all individu- known malarious area outside the country in which the als passively detected by health facilities and all those case was diagnosed; (2) local: a case for which the origin surveyed in follow-on reactive case detection (RACD) is likely from local transmission; (3) intraported: a case carried out between January 2010 and June 2014 and which has its origins in another part of Swaziland; and, map the reported domestic and international travel his- (4) unknown: where the information available does not tories. It also explores the diferences in travel patterns enable a case classifcation [19]. between confrmed positive cases, with those found to Te data used in this study are from the Swaziland be negative, and examined demographic, socio-economic Malaria Surveillance Database System (MSDS) and and geographic factors associated with any diferences. include data recorded between January 2010 and June 2014 for all index cases and between August 2012 and Methods June 2014 for all individuals tested for malaria as part In 2009, the Swaziland National Malaria Control Pro- of RACD in pre-defned receptive areas. Te data cov- gramme (NMCP) introduced active surveillance, consist- ers four full malaria seasons defned by the Swaziland ing of: (1) active case investigation at the household of NMCP: July 2010–June 2011, July 2011–June 2012, July the index case, triggered by parasitological confrmation 2012–June 2013, and July 2013–June 2014, with the addi- of a malaria case at a health facility; (2) RACD, triggered tion of half a season: January 2010–June 2010. Te data by the location of a confrmed malaria case in Swaziland’s were anonymized and the place of residence of each indi- receptive area; and, (3) pro-active case detection, trig- vidual and travel destination were georeferenced using gered by strong suspicion of malaria transmission within ArcGIS v10.2.2 [20]. Te geolocation of residences was a defned detection area and on high-risk populations, aggregated by localities, which is the relevant operational such as Mozambican farm workers [19] (Fig. 1). Every unit at which public health decisions are made in Swa- case that is parasitologically confrmed at health facilities ziland. Te travel destinations