Submicroscopic Plasmodium falciparum infections in pregnancy in Ghana

Abstract

SummaryMalarial parasitaemia below the threshold of microscopy but detectable by polymerase chain reaction (PCR) assays is common in endemic regions. This study was conducted to examine prevalence, predictors, and effects of submicroscopic Plasmodium falciparum infections in pregnancy. In a cross-sectional study among 530 pregnant women in Ghana, plasmodial infections were assessed by microscopy and PCR assays. Concentrations of haemoglobin and C-reactive protein (CRP) were measured and antimalarial drugs (chloroquine, pyrimethamine) in urine were demonstrated by ELISA dipsticks. By microscopy, 32% of the women were found to harbour malaria parasites. This rate increased to 63% adding the results of the parasite-specific PCR. P. falciparum was present in all but one infection. With increasing gravidity, infection rates and parasite densities decreased and the proportions of submicroscopic parasitaemia among infected women grew. Correspondingly, anaemia, fever and evidence of inflammation (CRP Ͼ 0.6 mg/dl) were more frequent in primigravidae than in multigravidae. Antimalarial drugs were detected in 65% of the women and were associated with a reduced prevalence of P. falciparum infections and a raised proportion of submicroscopic parasitaemia. Both gravidity and antimalarial drug use were independent predictors of submicroscopic P. falciparum infections. These infections caused a slight reduction of Hb levels and considerably increased serum concentrations of CRP. Conventional microscopy underestimates the actual extent of malarial infections in pregnancy in endemic regions. Submicroscopic P. falciparum infections are frequent and may contribute to mild anaemia and inflammation in seemingly aparasitaemic pregnant women.

Multiplicity of Plasmodium falciparum infection in pregnancy.

“…We cannot entirely rule out the possibility that the decreasing sensitivity of the PCR in detecting multiple infections at very low levels of parasitemia, which are common in women with a high number of pregnancies, 22 may have biased our results. Thus, the MOI may have been underestimated, particularly in multigravidae.…”

“…22 This region is holoendemic for malaria. 23 Ethical approval was given by the Ghanaian Ministry of Health and informed consent was obtained from the study participants.…”

Plasmodium falciparum dihydrofolate reductase alleles and pyrimethamine use in pregnant Ghanaian women.

“…[10][11][12][13] In a recent cross-sectional study on malaria in pregnancy in rural Ghana, intake of pyrimethamine as assessed by its detection in urine was associated with an only slightly lower rate of P. falciparum infection. 14 Here, we assessed P. falciparum DHFR gene alleles of isolates obtained from the study participants and analyzed the association between DHFR gene mutations and history and proof of pyrimethamine use. Moreover, we examined whether the clinical manifestation of resistant and sensitive parasites differed in women with and without pyrimethamine intake.…”

Challenges of malaria diagnosis in clinical settings and disease surveillance under reduced malaria burden in Tanzania

“…The contribution of submicroscopic infections to malaria transmission and febrile illness is likely to increase with declining malaria burden as a result of lowered naturally acquired immunity to malaria [45]. The role of submicroscopic infections in lowering hemoglobin levels has also been documented [46,47]. Cases of malarial illnesses due to submicroscopic parasitaemia are likely to be few, but they may be missed by routine microscopy and may be considered to be non-malarial, therefore receiving inappropriate treatment is likely to prolong the illness.…”