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Zanzibar has transitioned from malaria control to the pre-elimination phase, and the continued need for intermittent preventive treatment during pregnancy (IPTp) has been questioned. We conducted a prospective observational study to estimate placental malaria positivity rate among women who did not receive IPTp with sulfadoxinepyrimethamine. A convenience sample of pregnant women was enrolled from six clinics on the day of delivery from August of 2011 to September of 2012. Dried placental blood spot specimens were analyzed by polymerase chain reaction (PCR); 9 of 1, 349 specimens (0. 7%; precision estimate = 0. 2-1. 1%) were PCR-positive for Plasmodium falciparum. Placental infection was detected on both Pemba (N = 3) and Unguja (N = 6). Placental malaria positivity in Zanzibar was low, even in the absence of IPTp. It may be reasonable for the Ministry of Health to consider discontinuing IPTp, intensifying surveillance efforts, and promoting insecticide-treated nets and effective case management of malaria in pregnancy. Copyright © 2014 by The American Society of Tropical Medicine and Hygiene.
Zanzibar is comprised of two main islands approximately 40 km from mainland Tanzania: Unguja (2012 population = 896,721; 1,666 km2) and Pemba (2012 population = 406,848; 998 km2).15,16 This study was conducted at a purposive sample of 6 of 38 health facilities in Zanzibar where routine deliveries occur (3 facilities in Unguja [Mnazi Mmoja Hospital, Mwembeladu Hospital, and Kivunge Health Center] and 3 facilities in Pemba [Chake Chake Hospital, Wete Hospital, and Micheweni Health Center]) from August of 2011 to September of 2012. These facilities were engaged in an ongoing program supported by the US Agency for International Development (USAID) designed to improve maternal and newborn health services. Although these six hospitals covered approximately 82% of hospital deliveries on both islands, 50% of women in Zanzibar deliver at home.17 The peak rainfall period occurs from March to June, and the peak malaria transmission period is from April to July.18 Residents of Unguja or Pemba delivering at a study facility were considered eligible if their antenatal care (ANC) card indicated they had received no doses of IPTp SP. Women were enrolled 24 hours/day every day of the week by the clinic staff. Consecutive sampling was used to enroll all eligible women during the 12-month study period. However, because of the added burden on the clinic staff, no listing was maintained of women who were eligible but not enrolled. The 12-month enrollment ensured that both low- and high-transmission seasons were represented. Women who delivered at the six facilities were screened by examining their ANC card, which contains a designated space for recording doses of IPTp SP received. No additional questions were asked, because eligible clients were typically in active labor. Eligible women who agreed to participate were read an informed consent statement by trained maternity nurses or nurse midwives, and their verbal consent was obtained and recorded. No additional assent options were offered to minors. A brief form, including age of mother, gravidity, hemoglobin or hematocrit and week of gestation at which the measurement was taken, whether it was a singleton or multiple birth, outcome of the birth, and birth weight of the baby, was filled out by the health worker with information extracted from each consenting mother’s ANC card. The form was placed into the client’s file and transferred to the delivery room with the client. After management of the birth, a trained maternity nurse or nurse midwife at each facility obtained a placental dried blood spot (DBS) specimen from the maternal side of the placenta. A single deep incision was made, and five drops of blood were drawn up with a pipette and dotted onto Whatman 903 Protein Saver Card filter paper labeled only with the woman’s study identification (ID) number.19,20 DBS specimens were labeled, packed with desiccant, and transferred to the University of California, San Francisco for polymerase chain reaction (PCR) to detect infection with Plasmodium (all species). Although exact timing was not monitored, collection of each specimen generally occurred within 30 minutes of delivery. After collection of the specimen, the placenta was disposed of per the facility’s routine procedures. Multiple births were noted on the client’s study form. In the case of twins with one placenta, one ID was issued. In the case of twins with two placentas, each placenta was assigned a unique ID number and tested. Corresponding placental ID numbers were noted on the client form. DNA from each DBS was extracted using the QIAamp DNA Microkit following the manufacturer’s instructions (Qiagen, Germantown, MD). Plasmodium DNA was amplified by 18S ribosomal DNA PCR, with the species-specific nested round confirming falciparum species.21 The presence of PCR product was evaluated using agarose gel electrophoresis stained with ethidium bromide. Testing of control samples extracted from DBSs with known parasite densities confirmed a limit of detection of < 10 parasite/μL. The required sample size was calculated to be 1,825 assuming a parasitemia prevalence of 5% with a 95% confidence interval with precision of ±1% point. The sample size was calculated assuming independence of observations, because intracluster correlations could not be assessed, but the expected prevalence was liberally estimated to help account for unknown variables. Initial results indicated prevalence well under the liberal prevalence estimate used in the sample size assumptions, indicating that fewer samples were needed to attain the necessary power for the study, but data collection continued to allow for coverage throughout both the rainy and dry seasons. Client forms were entered into an Access database and date stamped, and hard copies were filed chronologically along with the consent forms. Data on PCR status were provided in an Excel spreadsheet, and the ID numbers were matched between the two files. Cleaned data were exported into SPSS, version 20 and Stata, version 11 for analysis. Although we attempted to enroll all eligible women, given the total number of deliveries and the expected proportion of women who did not receive IPTp (25%),14 it is likely that some of the eligible women were not enrolled. Given that the participants in this study were a non-probability sample of all eligible women, the 95% confidence interval given for the proportion of women with placental parasitemia who did not receive IPTp is considered a precision interval rather than a confidence interval. Ethical approval was provided by the Zanzibar Research Council, Johns Hopkins School of Public Health Institutional Review Board, and the US Centers for Disease Control and Prevention, Atlanta.
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