Tackling Imported Malaria: An Elimination Endgame

Abstract

As countries move toward malaria elimination, imported infections become increasingly significant as they often represent the majority of cases, can sustain transmission, cause resurgences, and lead to mortality. Here we review and critique current methods to prevent malaria importation in countries pursuing elimination and explore methods applied in other transmission settings and to other diseases that could be transferred to support malaria elimination. To improve intervention targeting we need a better understanding of the characteristics of populations importing infections and their patterns of migration, improved methods to reliably classify infections as imported or acquired locally, and ensure early and accurate diagnosis. The potential for onward transmission in the most receptive and vulnerable locations can be predicted through high-resolution risk mapping that can help malaria elimination or prevention of reintroduction programs target resources. Cross border and regional initiatives can be highly effective when based on an understanding of human and parasite movement. Ultimately, determining the optimal combinations of approaches to address malaria importation will require an evaluation of their impact, cost effectiveness, and operational feasibility.

Towards the implementation of malaria elimination policy in South Africa: the stakeholders’ perspectives

“…Cotter et al asserted that imported malaria cases should be addressed to achieve malaria elimination [5], as they were the reasons for resurgences in the elimination setting of Zanzibar [14]. Effective control of imported malaria cases requires strong cross-border collaboration with the neighbouring malaria endemic countries.…”

“…Consequently, South Africa, Swaziland, Namibia and Botswana were the first countries declared as ready to target malaria elimination (defined as no local malaria transmission in a defined geographical area) in southern Africa [10,11]. The Lubombo Spatial Development Initiative (LSDI – the cross-border malaria control collaboration between Mozambique, Swaziland and South Africa) has been partly lauded for these reductions [5,12–14]. Malaria cases and deaths in South Africa dropped by 89.4% and 85.4%, respectively, between 2000 and 2010 [15].…”

The Hitchhiking Parasite: Why Human Movement Matters to Malaria Transmission and What We Can Do About It

“…Within this context, an understanding of human movement is essential to determine how best to optimize control strategies by targeting: (i) sources of transmission; (ii) conduits of travel by high-risk travelers; and (iii) receptive locations vulnerable to outbreaks as a result of importation [2]. While human movement is ubiquitous across transmission settings, it is a particular concern in locations where local transmission has been reduced but the environment is still conducive to transmission [1,3].…”

“…Shortcomings of this approach are: (i) the parasite may have been contracted before or after the trip; (ii) many imported cases are missed by passive reporting systems because they are asymptomatic or simply not reported; and (iii) some key traveler groups, such as forest workers in Southeast Asia, are under-represented because they are less likely to attend health facilities. Furthermore, the timeframe used to determine whether an infection is imported varies between 18 days and 3 months, depending on the country, making it difficult to compare malaria burdens due to importation [2].…”

“…A key to maintaining recent gains in malaria control in low transmission settings and progressing to elimination is to realize that imported infections can be minimized at any of four stages of human movement: during outgoing travel; at the high transmission setting (source); during return travel; and upon return to the low transmission setting [2] (Figure 2). …”