Targeting Pregnant Women for Malaria Surveillance

Abstract

Women attending antenatal care (ANC) are a generally healthy, easy-access population, contributing valuable data for infectious disease surveillance at the community level. ANC-based malaria surveillance would provide a routine measure of the malaria burden in pregnancy, which countries lack, whilst potentially improving pregnancy outcomes. It could also offer contemporary information on temporal trends and the geographic distribution of malaria burden as well as intervention coverage in the population to guide resource allocation and to assess progress towards elimination. Here, we review the factors underlying the relationship between Plasmodium falciparum in pregnancy and in the community, and outline strengths and limitations of an ANC-based surveillance in sub-Saharan Africa, its potential role within wider malaria surveillance systems, and subsequent programmatic applications.

Keywords: antenatal care; malaria; pregnancy; surveillance.

Figure 1.. Advantages and disadvantages of using women at ANC clinics as sentinel populations for malaria surveillance over other surveillance methods.

The figure represents the pros and cons of P. falciparum surveillance at ANC clinics compared to main surveillance approaches operating in sub-Saharan Africa. The primary source to estimate malaria burden in Africa has been population-based health surveys (top), usually undertaken at the province level at widely spaced intervals due to operational challenges and high cost. Passive surveillance of malaria cases (left) through appropriate health management information systems (HMIS) offers more granular and contemporaneous data on a routine basis. Although HMIS are already stablished in most African countries and are a key focus of National Malaria Control Programs, the quality of data has often been poor with a general lack of timeliness, completeness and accuracy [61, 62]. Moreover, meaningful incidence rates require good estimates of the size of the health catchment population, which is unlikely to be available in many parts of sub-Saharan Africa [63]. As an alternative to incidence, test positivity rate (TPR) is likely to be affected by the rates of non-malarial febrile illness [37]. Thus, any estimates of burden derived from passive case systems are likely to be highly sensitive to health seeking behaviors, the decisions to test and the burden of asymptomatic infections. An ANC-based surveillance of malaria (right) would require to set up a new surveillance system and additional resources for testing and treatment. However, the numerical superiority and continuous nature of ANC data, compared to standard national surveys, would likely provide substantial potential applications while being less affected by variations in health seeking behaviors, as women do attend ANC clinics because they are pregnant rather than due to illness. Routine testing at first ANC visit would also reduce biases associated with decisions to test and provide information about asymptomatic infections. Moreover, as malaria surveillance at ANC clinics would measure prevalence, the estimates would be more stable to misspecification of population denominator, offering a valuable information to complement existing surveillance systems in Africa. Abbreviations: ANC, Antenatal care; MiP: Malaria in pregnancy; RDT: Rapid diagnostic test; TPR: Test positivity rate.

Figure 2.. Potential uses and added value of an ANC-based surveillance for malaria.

At first antenatal contact, data on malaria infection can be collected in a continuous way as part of routine services without requiring any additional sampling, together with screening for HIV, syphilis, and anaemia. Malaria screening at ANC would provide a routine measure of the malaria burden in pregnancy, which countries lack, whilst potentially improving pregnancy outcomes. As ANC clinics are well distributed and most African women attend them at least once, they could potentially increase resolution and precision of estimates generated through national surveys. Continuous (year-round) surveillance at ANC clinics may provide contemporary information on temporal trends, the geographic distribution of malaria burden, signals of sustained decreases in transmission due to an intervention (e.g, seasonal malaria chemoprevention) and early warning signals to rises in transmission. The recording of information about the use of malaria preventive measures could potentially allow a real-time assessment of intervention coverage in the population to guide resource allocation and to assess progress towards elimination. Antibodies against VAR2CSA, which are developed after exposures to placental parasites, may provide an adjunct to detect recent infections or document historical changes in transmission. Finally, women attending ANC may also constitute a convenient sampling population for the assessment of the parasite genetic make-up (i.e., complexity of infection), drug resistance gene flow between populations and adaptations developed by the parasite to control strategies, such as antimalarial resistance and deletions of antigens targeted by rapid diagnostic test that can compromise diagnosis, treatment and prevention.

Figure I.

ANC attendance in sub-Saharan Africa (data obtained from )