**1. Introduction**

In the Greater Mekong Subregion (GMS)1 , malaria is still a substantial public health problem, especially along international borders and forested areas, adversely putting populations such as migrants, refugees, and forest workers most at risk. In 2013, there were 447,800 malaria cases and 342 deaths in the GMS, with close to 700 million people living in risk areas [1]. Between 2012 and 2016, the reported number of malaria cases in the GMS fell by 74% (**Figure 1**) and malaria deaths by 91% in the same period (**Figure 2**).

These goals will not be easy to achieve. Despite these reductions and the subsequent move towards elimination, malaria remains an important cause of morbidity for an estimated 32 million inhabitants, especially in remote areas with low population densities and limited healthcare services and infrastructure, located in and near forested areas, which often lie close to international borders [3, 4]. In many places, the population groups most affected are ethnic minorities and forest-goers who are rapidly becoming the most important source of transmission in areas where main vectors are present. Within these groups, cultural and linguistic barriers often constrain malaria control efforts due to their high mobility and low access to

Human and Simian Malaria in the Greater Mekong Subregion and Challenges for Elimination

http://dx.doi.org/10.5772/intechopen.76901

97

In some areas the malaria situation has deteriorated by armed conflict affecting access to malaria control services. Population movements are a key feature in the GMS and are largely occupationally/economically driven; occur within borders and across borders; involve multiple factors and complex dynamics of movement; and affect different subsets of moving populations [5], thus further complicating the epidemiology and control of the disease [6]. The rapid increase in the number of large infrastructure and agricultural development projects in the region is also having a significant impact on the epidemiology of communicable diseases in general, and malaria in particular [7]. This chapter addresses several key challenges faced by elimination programmes to contain the unacceptably high disease burden against

**2. Resistance to artemisinin and ACT: current and future approaches**

Antimalarial drug resistance is not a new biological phenomenon. In the 1970s and 1980s, *Plasmodium falciparum*—the parasite species responsible for the most common and deadliest form of malaria—developed widespread resistance to previous antimalarial medicines, such as chloroquine and sulfadoxine-pyrimethamine (SP) [8]. Artemisinin based combination therapies (ACTs), introduced in the 1990s, are currently the most effective antimalarial drugs [9] and represent the first line-treatment for uncomplicated falciparum malaria in all endemic countries. Although artemisinin usually kills all malaria parasites, the use of a combination of drugs as opposed to monotherapy—helps ensure that any remaining parasites will be killed by the partner drug before the resistant parasites can spread. According to the World Health Organisation (WHO), clinical artemisinin (and its derivatives) resistance is defined as delayed parasite clearance and represents a partial/relative resistance that has thus far only affected ring-stage malaria parasites [10]. In Southeast Asia, however, some malaria parasites have already developed resistance to artemisinin-based drugs; a recent report of a single multidrug resistant malaria parasite lineage (PfPailin) with associated piperaquine resistance in Vietnam and its implications of subsequent transnational spread is of international concern [11]. Artemisinin resistance was first reported along the Thailand-Cambodia border in 2008 [12, 13] and has continued to spread in all Greater Mekong Subregion countries [14–18]. In addition, artemisinin resistance has been involved in selecting for resistance to ACT partner drugs, resulting in high late treatment failure rates with dihydroartemisinin-piperaquine in Cambodia [14, 19–25] and with artesunate-mefloquine on the Thai-Myanmar border [26].

interventions to prevent, diagnose and treat malaria.

the background of rapidly declining incidence.

Mid-year estimates for 2017 point to a further decline in cases [2]. Contributing to these impressive results, all six countries of the Subregion are making significant headway towards a common target: eliminating malaria by the year 2030 at the latest.

**Figure 1.** Declining trends of malaria transmission in the Greater Mekong Subregion (GMS) since 2012 (source: [2]).

<sup>1</sup> Cambodia, The People's Republic of China (specifically Yunnan Province), the Lao People's Democratic Republic (Lao PDR), Myanmar, Thailand, and Vietnam.

These goals will not be easy to achieve. Despite these reductions and the subsequent move towards elimination, malaria remains an important cause of morbidity for an estimated 32 million inhabitants, especially in remote areas with low population densities and limited healthcare services and infrastructure, located in and near forested areas, which often lie close to international borders [3, 4]. In many places, the population groups most affected are ethnic minorities and forest-goers who are rapidly becoming the most important source of transmission in areas where main vectors are present. Within these groups, cultural and linguistic barriers often constrain malaria control efforts due to their high mobility and low access to interventions to prevent, diagnose and treat malaria.

**1. Introduction**

96 Towards Malaria Elimination - A Leap Forward

1

PDR), Myanmar, Thailand, and Vietnam.

In the Greater Mekong Subregion (GMS)1

, malaria is still a substantial public health prob-

lem, especially along international borders and forested areas, adversely putting populations such as migrants, refugees, and forest workers most at risk. In 2013, there were 447,800 malaria cases and 342 deaths in the GMS, with close to 700 million people living in risk areas [1]. Between 2012 and 2016, the reported number of malaria cases in the GMS fell by 74%

Mid-year estimates for 2017 point to a further decline in cases [2]. Contributing to these impressive results, all six countries of the Subregion are making significant headway towards

Cambodia, The People's Republic of China (specifically Yunnan Province), the Lao People's Democratic Republic (Lao

**Figure 2.** Declining trend of malaria deaths in the Greater Mekong Subregion (GMS) since 2012 (source: [2]).

**Figure 1.** Declining trends of malaria transmission in the Greater Mekong Subregion (GMS) since 2012 (source: [2]).

(**Figure 1**) and malaria deaths by 91% in the same period (**Figure 2**).

a common target: eliminating malaria by the year 2030 at the latest.

In some areas the malaria situation has deteriorated by armed conflict affecting access to malaria control services. Population movements are a key feature in the GMS and are largely occupationally/economically driven; occur within borders and across borders; involve multiple factors and complex dynamics of movement; and affect different subsets of moving populations [5], thus further complicating the epidemiology and control of the disease [6]. The rapid increase in the number of large infrastructure and agricultural development projects in the region is also having a significant impact on the epidemiology of communicable diseases in general, and malaria in particular [7]. This chapter addresses several key challenges faced by elimination programmes to contain the unacceptably high disease burden against the background of rapidly declining incidence.
