Malaria resurgence: a systematic review and assessment of its causes

Abstract

Background: Considerable declines in malaria have accompanied increased funding for control since the year 2000, but historical failures to maintain gains against the disease underscore the fragility of these successes. Although malaria transmission can be suppressed by effective control measures, in the absence of active intervention malaria will return to an intrinsic equilibrium determined by factors related to ecology, efficiency of mosquito vectors, and socioeconomic characteristics. Understanding where and why resurgence has occurred historically can help current and future malaria control programmes avoid the mistakes of the past.

Methods: A systematic review of the literature was conducted to identify historical malaria resurgence events. All suggested causes of these events were categorized according to whether they were related to weakened malaria control programmes, increased potential for malaria transmission, or technical obstacles like resistance.

Results: The review identified 75 resurgence events in 61 countries, occurring from the 1930s through the 2000s. Almost all resurgence events (68/75 = 91%) were attributed at least in part to the weakening of malaria control programmes for a variety of reasons, of which resource constraints were the most common (39/68 = 57%). Over half of the events (44/75 = 59%) were attributed in part to increases in the intrinsic potential for malaria transmission, while only 24/75 (32%) were attributed to vector or drug resistance.

Conclusions: Given that most malaria resurgences have been linked to weakening of control programmes, there is an urgent need to develop practical solutions to the financial and operational threats to effectively sustaining today's successful malaria control programmes.

Figure 1

PRISMA[78]systematic review identification, screening, eligibility, and inclusion.

Figure 2

The blue line represents slide positivity (left axis) and the pink bars depict the number of houses sprayed with IRS per 1,000 population [54,79]. Gray bars represent averages of surrounding years where no data on IRS was available in a particular year (otherwise the lack of a bar indicates zero houses sprayed).

Figure 3

Malaria resurgence in Asia and Eastern Europe followed weakening – both intentional and accidental – of malaria control programmes. Resurgence followed general deterioration of control programmes in Bhutan, Indonesia [20,80], Pakistan [81], and Solomon Islands [82]; purposeful weakening of activities in Nepal, Sri Lanka, and Thailand [20,80]; and insufficient funding and resources for vector control in India [20,80] and Turkey [83].

Figure 4

Malaria resurgence has followed war, population movement, and associated disruptions in Europe and Asia. Resurgences followed wars and social tumult in Spain, Italy [5], Tajikistan, Azerbaijan, Armenia [83], Bangladesh, Myanmar, and Sri Lanka [20,80], and began in soldiers in the demilitarized zone in Republic of Korea [84,85].

Figure 5

Malaria resurgence in Africa followed cessation of pilot programmes and relaxation of control activities. Cessation of pilot programmes in Pare-Taveta [86,87], Garki [35], and Gezira [5] resulted in rapid resurgence to baseline levels, while weakening or halting of control activities in Kapsabet in the western Kenyan highlands [19], Zanzibar (twice) [9], Mauritius [27], Madagascar [40], and Swaziland [88] similarly led to the return of malaria in these areas.