Pregnant women and infants as sentinel populations to monitor prevalence of malaria: results of pilot study in Lake Zone of Tanzania

Abstract

Background: As malaria control interventions are scaled-up, rational approaches are needed for monitoring impact over time. One proposed approach includes monitoring the prevalence of malaria infection among pregnant women and children at the time of routine preventive health facility (HF) visits. This pilot explored the feasibility and utility of tracking the prevalence of malaria infection in pregnant women attending their first antenatal care (ANC) visit and infants presenting at 9-12 months of age for measles vaccination.

Methods: Pregnant women attending first ANC and infants nine to 12 months old presenting for measles vaccination at a non-probability sample of 54 HFs in Tanzania's Lake Zone (Mara, Mwanza and Kagera Regions) were screened for malaria infection using a malaria rapid diagnostic test (RDT) from December 2012 to November 2013, regardless of symptoms. Participants who tested positive were treated for malaria per national guidelines. Data were collected monthly.

Results: Overall 89.9 and 78.1 % of expected monthly reports on malaria infection prevalence were received for pregnant women and infants, respectively. Among 51,467 pregnant women and 35,155 infants attending routine preventive HF visits, 41.2 and 37.3 % were tested with RDT, respectively. Malaria infection prevalence was 12.8 % [95 % confidence interval (CI) 11.3-14.3] among pregnant women and 11.0 % (95 % CI 9.5-12.5) among infants, and varied by month. There was good correlation of the prevalence of malaria among pregnant women and infants at the HF level (Spearman rho = 0.6; p < 0.001). This approach is estimated to cost $1.28 for every person tested, with the RDT accounting for 72 % of the cost.

Conclusions: Malaria infection was common and well correlated among pregnant women and infants attending routine health services. Routine screening of these readily accessible populations may offer a practical strategy for continuously tracking malaria trends, particularly seasonal variation. Positivity rates among afebrile individuals presenting for routine care offer an advantage as they are unaffected by the prevalence of other causes of febrile illness, which could influence positivity rates among febrile patients presenting to outpatient clinics. The data presented here suggest that in addition to contributing to clinical management, ongoing screening of pregnant women could be used for routine surveillance and detection of hotspots.

Keywords: Infants; Malaria surveillance; Pregnant women; Sentinel population; Tanzania.

Fig. 1

Geographic location of health facilities participating in the study, Mwanza, Mara and Kagera regions

Fig. 2

Distribution of reporting by RCH clinics, testing for malaria and malaria positivity among pregnant women and infants by region, December 2012–November 2013. Pregnant women: a proportion of RCH clinics reporting; b proportion tested for malaria; c proportion positive for malaria. Infants aged 9–12 months: d proportion of RCH clinics reporting; e proportion tested for malaria; f proportion positive for malaria

Fig. 3

Geographical variation in RCH clinics attendance, malaria testing and malaria prevalence among pregnant women and infants by district. Pregnant women: a number attending RCH clinics; b proportion tested for malaria; c proportion positive for malaria. Infants aged 9–12 months: d number attending RCH clinics; e proportion tested for malaria; f proportion positive for malaria

Fig. 4

Malaria positivity among patients attending outpatient clinic in 54 health facilities participating in sentinel surveillance

Fig. 5

a Scatter plot of positivity rate at the outpatient department versus the prevalence among enrolled pregnant women. Spearman’s test: Kagera (rho 0.4, p < 0.001), Mara (rho = 0.2, p = 0.1), Mwanza (rho = 0.3, p = 0.36), Total (rho = 0.3, p < 0.001). b Scatter plot of positivity rate at the outpatient department versus the prevalence among enrolled infants. Spearman’s test: Kagera (rho = 0.4, p = 0.002), Mara (rho 0.5, p = 0.001), Mwanza (rho = 0.6, p < 0.001), Total (rho = 0.4, p < 0.001)