Between 2012 and 2016, two cross-sectional surveys per year in relation to the malaria transmission season were carried out: one just before start (June) and the other at the end (January) of the season (for the year 2016, start of season survey was not conducted due to logistical challenges). Only individuals enrolled into the study were sampled at every survey; demographic and clinical information which included history of fever and symptoms suggestive of clinical malaria in the previous 48 h and at time of survey was collected using a structured questionnaire. Axillary temperature was measured by a digital clinical thermometer. A malaria rapid diagnostic test (RDT) (SD Bioline®) was performed for participants with suspected clinical malaria based on clinical assessment and if positive were treated according to the national guidelines.
A blood sample was collected by fingerpick for microscopy and for measuring haemoglobin. Thick blood films were stained with 2.5% buffered Giemsa (PH 7.2) for 10–15 min, dried and read independently by two microscopists. If a slide was positive, parasites were counted against 500 white blood cells (WBCs) and parasite densities estimated assuming 8000 WBC per µl. Slides were considered negative after examining 200 high power fields. If the estimation of the parasite count between the two independent microscopists differed by ≥ 20% or if readings were discrepant for positivity, a third microscopist resolved the discrepancy. Asymptomatic P. falciparum carriage was defined as asexual parasitaemia of any density detected by microscopy without symptoms suggestive of clinical malaria within the previous 48 h or at time of assessment during survey. Haemoglobin was measured using a HemoCue® photometer (Ångelholm, Sweden) according to manufacturer’s instruction. A study clinic in the health centre of the study area was established where all study participants sought medical care for any illness during the study period. During each malaria transmission season (August to January), a passive case detection (PCD) system was established where suspected cases of clinical malaria were clinically assessed and systematically screened with malaria RDT (SD Bioline®). Positive cases were treated according to the national treatment guidelines. Usage of ITN was assessed by asking all participants attending the study clinic, regardless of their illness, if they had slept under an ITN the previous night.
A blood sample was collected by fingerpick for microscopy and for measuring haemoglobin. Thick blood films were stained with 2.5% buffered Giemsa (PH 7.2) for 10–15 min, dried and read independently by two microscopists. If a slide was positive, parasites were counted against 500 white blood cells (WBCs) and parasite densities estimated assuming 8000 WBC per µl. Slides were considered negative after examining 200 high power fields. If the estimation of the parasite count between the two independent microscopists differed by ≥ 20% or if readings were discrepant for positivity, a third microscopist resolved the discrepancy. Asymptomatic P. falciparum carriage was defined as asexual parasitaemia of any density detected by microscopy without symptoms suggestive of clinical malaria within the previous 48 h or at time of assessment during survey. Haemoglobin was measured using a HemoCue® photometer (Ångelholm, Sweden) according to manufacturer’s instruction. A study clinic in the health centre of the study area was established where all study participants sought medical care for any illness during the study period. During each malaria transmission season (August to January), a passive case detection (PCD) system was established where suspected cases of clinical malaria were clinically assessed and systematically screened with malaria RDT (SD Bioline®). Positive cases were treated according to the national treatment guidelines. Usage of ITN was assessed by asking all participants attending the study clinic, regardless of their illness, if they had slept under an ITN the previous night.
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