Associations between peripheral Plasmodium falciparum malaria parasitemia, human immunodeficiency virus, and concurrent helminthic infection among pregnant women in Malawi

Approximately 2 billion persons worldwide are infected with schistosomiasis and soil-transmitted helminths (STH), many in areas where endemic malaria transmission coexists. Few data exist on associations between these infections. Nested within a larger clinical trial, primigravid and secundigravid women provided blood samples for human immunodeficiency virus (HIV) testing and peripheral malaria films and stool and urine for evaluation of STH and Schistosoma spp. during their initial antenatal clinic visit. The most common parasitic infections were malaria (37.6%), S. haematobium (32.3%), and hookworm (14.4%); 14.2% of women were HIV-infected. S. haematobium infection was associated with lower malarial parasite densities (344 versus 557 parasites/μL blood; P < 0.05). In multivariate analysis, HIV and hookworm infection were independently associated with malaria infection (adjusted odds ratio = 1.9 and 95% confidence interval = 1.2-3.0 for HIV; adjusted odds ratio = 1.9 and 95% confidence interval = 1.03-3.5 for hookworm). Concurrent helminthic infection had both positive and negative effects on malaria parasitemia among pregnant women in Malawi.

Comparative population structure of Plasmodium malariae and Plasmodium falciparum under different transmission settings in Malawi

Background

Described here is the first population genetic study of Plasmodium malariae, the causative agent of quartan malaria. Although not as deadly as Plasmodium falciparum, P. malariae is more common than previously thought, and is frequently in sympatry and co-infection with P. falciparum, making its study increasingly important. This study compares the population parameters of the two species in two districts of Malawi with different malaria transmission patterns - one seasonal, one perennial - to explore the effects of transmission on population structures.

Methods

Six species-specific microsatellite markers were used to analyse 257 P. malariae samples and 257 P. falciparum samples matched for age, gender and village of residence. Allele sizes were scored to within 2 bp for each locus and haplotypes were constructed from dominant alleles in multiple infections. Analysis of multiplicity of infection (MOI), population differentiation, clustering of haplotypes and linkage disequilibrium was performed for both species. Regression analyses were used to determine association of MOI measurements with clinical malaria parameters.

Results

Multiple-genotype infections within each species were common in both districts, accounting for 86.0% of P. falciparum and 73.2% of P. malariae infections and did not differ significantly with transmission setting. Mean MOI of P. falciparum was increased under perennial transmission compared with seasonal (3.14 vs 2.59, p = 0.008) and was greater in children compared with adults. In contrast, P. malariae mean MOI was similar between transmission settings (2.12 vs 2.11) and there was no difference between children and adults. Population differentiation showed no significant differences between villages or districts for either species. There was no evidence of geographical clustering of haplotypes. Linkage disequilibrium amongst loci was found only for P. falciparum samples from the seasonal transmission setting.

Conclusions

The extent of similarity between P. falciparum and P. malariae population structure described by the high level of multiple infection, the lack of significant population differentiation or haplotype clustering and lack of linkage disequilibrium is surprising given the differences in the biological features of these species that suggest a reduced potential for out-crossing and transmission in P. malariae. The absence of a rise in P. malariae MOI with increased transmission or a reduction in MOI with age could be explained by differences in the duration of infection or degree of immunity compared to P. falciparum.

Effect of transmission setting and mixed species infections on clinical measures of malaria in Malawi

Background

In malaria endemic regions people are commonly infected with multiple species of malaria parasites but the clinical impact of these Plasmodium co-infections is unclear. Differences in transmission seasonality and transmission intensity between endemic regions have been suggested as important factors in determining the effect of multiple species co-infections.

Principal Findings

In order to investigate the impact of multiple-species infections on clinical measures of malaria we carried out a cross-sectional community survey in Malawi, in 2002. We collected clinical and parasitological data from 2918 participants aged >6 months, and applied a questionnaire to measure malaria morbidity. We examined the effect of transmission seasonality and intensity on fever, history of fever, haemoglobin concentration ([Hb]) and parasite density, by comparing three regions: perennial transmission (PT), high intensity seasonal transmission (HIST) and low intensity seasonal transmission (LIST). These regions were defined using multi-level modelling of PCR prevalence data and spatial and geo-climatic measures. The three Plasmodium species (P. falciparum, P. malariae and P. ovale) were randomly distributed amongst all children but not adults in the LIST and PT regions. Mean parasite density in children was lower in the HIST compared with the other two regions. Mixed species infections had lower mean parasite density compared with single species infections in the PT region. Fever rates were similar between transmission regions and were unaffected by mixed species infections. A history of fever was associated with single species infections but only in the HIST region. Reduced mean [Hb] and increased anaemia was associated with perennial transmission compared to seasonal transmission. Children with mixed species infections had higher [Hb] in the HIST region.

Conclusions

Our study suggests that the interaction of Plasmodium co-infecting species can have protective effects against some clinical outcomes of malaria but that this is dependent on the seasonality and intensity of malaria transmission.

Characterization and application of multiple genetic markers for Plasmodium malariae

Plasmodium malariae, a protozoan parasite that causes malaria in humans, has a global distribution in tropical and subtropical regions and is commonly found in sympatry with other Plasmodium species of humans. Little is known about the genetics or population structure of P. malariae. In the present study, we describe polymorphic genetic markers for P. malariae and present the first molecular epidemiological data for this parasite. Six microsatellite or minisatellite markers were validated using 76 P. malariae samples from a diverse geographical range. The repeat unit length varied from 2 to 17 bp, and up to 10 different alleles per locus were detected. Multiple genotypes of P. malariae were detected in 33 of 70 samples from humans with naturally acquired infection. Heterozygosity was calculated to be between 0.236 and 0.811. Allelic diversity was reduced for samples from South America and, at some loci, in samples from Thailand compared with those from Malawi. The number of unique multilocus genotypes defined using the 6 markers was significantly greater in Malawi than in Thailand, even when data from single genotype infections were used. There was a significant reduction in the multiplicity of infection in symptomatic infections compared with asymptomatic ones, suggesting that clinical episodes are usually caused by the expansion of a single genotype.

Association between the pharmacokinetics and in vivo therapeutic efficacy of sulfadoxine-pyrimethamine in Malawian children

Sulfadoxine-pyrimethamine (SP) has been widely used in recent years to treat acute uncomplicated Plasmodium falciparum malaria. Risk factors for SP therapeutic failure include young age, subtherapeutic SP concentrations, and resistance-conferring genetic mutations in parasite target enzymes. A substantial proportion of patients are able to clear genetically highly resistant P. falciparum genotypes. To determine whether blood SP concentrations independently affect the patient's ability to clear resistant genotypes, we compared SP pharmacokinetics of cases of adequate clinical and parasitological response (ACPR) with cases of treatment failure (TF). When patients with ACPR and TF were compared, mean values were similar for the day 3 blood pyrimethamine (205 ng/ml versus 172 ng/ml; P = 0.25) and estimated maximum sulfadoxine (79 +/- 6.52 versus 69 +/- 6.27 mug/ml; P = 0.60) concentrations, for sulfadoxine terminal-phase elimination half-lives (7.15 versus 6.41 days; P = 0.42), and for the extents of sulfadoxine absorption (areas under the concentration-time curve of 932 +/- 100 versus 888 +/- 78.9 mug day ml(-1); P = 0.72). Among patients infected with the quintuple resistant parasites, day 3 blood pyrimethamine concentrations were higher in those who cleared the infection than in those who did not (305 +/- 35.4 versus 228 +/- 21.7 ng/ml; P = 0.037). Within this subgroup, this finding remained significant after adjusting for endogenous folate levels, age, site, and resistance-conferring mutations (odds ratio: 1.011 [1.003 to 1.024]; P = 0.018). However, as a subgroup analysis, our biologically plausible observation that higher blood pyrimethamine concentrations enhance the ability of patients to clear resistant P. falciparum should be interpreted with caution and needs further validation.

Blood folate concentrations and in vivo sulfadoxine-pyrimethamine failure in Malawian children with uncomplicated Plasmodium falciparum malaria

Folate antagonizes the antimalarial action of sulfadoxine-pyrimethamine (SP) in vitro, but its role in vivo is not well understood. We measured blood folate concentrations and SP therapeutic outcomes in Malawian children. Children with late treatment failure and those with adequate clinical and parasitologic responses had similar demographic characteristics, prevalence of parasite mutations conferring resistance to SP, and blood concentrations of anti-malarial drugs following treatment. However, a higher folate concentration was associated with late treatment failure. Patients from a low malaria transmission site had higher blood folate concentrations than those in a higher transmission site (mean +/- SEM = 39 +/- 9.3 ng/mL versus 29 +/- 10 ng/mL; P < 0.0001), and there was a higher rate of late treatment failure in the low transmission area (54.4% versus 40.2%; P = 0.010). This study also provides the first evidence of the independent role of physiologic folate concentrations in in vivo SP therapeutic efficacy, and the critical role of pyrimethamine concentrations in the therapeutic efficacy of SP when one controls physiologic folate levels and the frequency of critical dihydrofolate reductase/dihydropteroate synthase mutations.

Care seeking behaviour and treatment of febrile illness in children aged less than five years: a household survey in Blantyre District, Malawi

Malaria is a leading cause of death in children aged < 5 years in Malawi. As part of the Roll Back Malaria initiative, African heads of state have pledged that by 2005, 60% of children will receive an effective antimalarial drug within 24 h of developing fever. In 1993, Malawi switched from chloroquine to sulfadoxine-pyrimethamine (SP) in its recommendations of home treatment of febrile illness in children. To study care seeking behaviour and home treatment in Blantyre District, and provide valuable follow-up to the chloroquine to SP transition, we performed a 2-stage cluster-sample survey in February 2000. Our sample of 1080 households included 672 households with children aged < 5 years; 292 (32.2%, 95% CI 28.7-35.8%) of the 912 children in these households had completed a febrile episode within the past 14 d. Among recently febrile children, 210 (72.0%, 95% CI 67.0-77.1%) received medication at home during their illness, but only 36 (12.2%, 95% CI 8.4-16.0%) received an appropriate antimalarial drug. Overall, 111 (37.4%, 95% CI 30.9-43.9%) received prompt, appropriate treatment. Only rural location was statistically associated with failure to receive prompt appropriate treatment (risk ratio estimate 1.2, 95% CI 1.01-1.5). A greater effort to improve the quality of malaria home treatment or to expand health facility utilization will be necessary to achieve Roll Back Malaria goals before 2005 in Blantyre District. Current care seeking practices suggest interventions should stress promptness of health facility visits, improved access to appropriate drugs, and accurate dosing for home-based treatments.

Use of antenatal care services and intermittent preventive treatment for malaria among pregnant women in Blantyre District, Malawi

Malaria in pregnancy contributes to low birth weight and increased infant mortality. As part of WHO's Roll Back Malaria initiative, African heads of state pledged that by 2005, 60% of pregnant women will receive malaria chemoprophylaxis or intermittent preventive treatment (IPT). We performed a cluster sample survey to study the use of sulfadoxine-pyrimethamine (SP) for IPT among recently pregnant women in February 2000 in Blantyre District, Malawi. Among 391 women in the sample, 98.6% had attended antenatal clinic at least once and 90.2% knew that SP/IPT was recommended during pregnancy. Overall, only 36.8% received the full recommended two-dose regimen of SP/IPT. Using data from 187 women with antenatal clinic cards, we found that residence location, housing type and gender/age/education of the head of household were not associated with failure to receive SP/IPT. Adjusting for education, multigravid women were more likely not to receive the recommended SP/IPT regimen (RR 1.2, 95% CI 1.02-1.5, P=0.03). A substantial effort to improve the delivery and use of SP/IPT in Malawi will be necessary, but the Roll Back Malaria 2005 goal appears achievable.

Insecticide-treated bednet use, anaemia, and malaria parasitaemia in Blantyre District, Malawi

OBJECTIVE

To evaluate the use of insecticide-treated bednets and the effectiveness of social marketing for their distribution.

METHODS

Systematic cluster sample survey of 1080 households in 36 census enumeration areas across Blantyre district, Malawi, in February 2000.

RESULTS

A total of 672 households had one or more children under 5. Bednet ownership was low (20.5% of households) overall, and significantly lower in rural areas than urban areas (6.4 vs. 29.8%, P=0.001). Only 3.3% of rural children under 5 had slept under a net the previous night, compared with 24.0% of urban children (P < 0.001). When asked why they did not own a net, nearly all (94.9%) caretakers in households without nets stated they had no money to buy them. In multivariate statistical models that controlled for the influence of house structure, urban vs. rural location, gender of the head of household, and the primary caretaker's education, rural children under 5 in households without nets experienced a statistically significant higher prevalence of malaria parasitaemia [RR (risk ratio) 4.9, 95% CI (confidence interval) 2.3-10.5] than children in households with at least one bednet. This was also true for urban children under 5 (RR 2.1, 95% CI 1.0-4.2, P=0.04).

CONCLUSION

Social marketing approaches to promoting insecticide-treated nets in Blantyre District may have produced measurable health benefits for children in those households in which residents bought and used the products. Market-based approaches may take years to achieve high levels of coverage and may exaggerate inequities between urban and rural populations.

Efficacy of mefloquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated Plasmodium falciparum infection in Machinga District, Malawi, 1998

In response to the spread of chloroquine-resistant Plasmodium falciparum, Malaŵi changed its first-line antimalarial drug in 1993 from chloroquine to sulfadoxine-pyrimethamine (SP). Surveillance data has suggested that resistance to SP may be increasing. We compared the efficacy of SP with a potential successor, mefloquine (MQ). By use of a modified World Health Organization in vivo protocol, children infected with P. falciparum were randomized to receive SP (sulfadoxine 25 mg/kg) or MQ (15 mg/kg). We observed combined RII and RIII parasitologic failures of 20.0 and 22.0% in the SP and MQ arms, respectively. Among those in the MQ arm, the relative hazard of failing with a Day 2 drug level < 500 ng/mL was 10.6 times higher than those with levels > or = 500 ng/mL. Given the decreased efficacy of the first-line antimalarial drug and the high failure rates of MQ at this lower dosage, Malaŵi should consider assessing the efficacy and feasibility of alternative drugs to treat uncomplicated falciparum malaria.

Malaria infection in infancy in rural Malawi

Malaria infection is thought to be relatively infrequent in infants less than 90 days of age in sub-Saharan Africa. In a rural area of Malawi with intense malaria transmission, we examined the occurrence of malaria infection during infancy and risk factors for parasitemia in the first three months of life in the cohort of infants delivered to women in the Mangochi Malaria Research Project. Among 3,915 liveborn singleton infants, 3,432 (87.7%) were seen at least once during infancy (first 12 months of life); of these, malaria blood smear results were available on 2,649 (77.2%). Overall, in a cross-sectional analysis, 23.3% of infants at three months of age were infected with Plasmodium falciparum; this proportion increased to more than 30% during the high transmission season. By the age of 10 months, 60-80% of the infants were infected, depending on the season. Geometric mean parasite density increased each month after two months of age and plateaued at seven months of age. In a life-table analysis, the median time to acquisition of a positive smear was 199 days. Factors independently associated with smear positivity at < 4 months of age included visit during high transmission season (adjusted odds ratio [AOR] = 4.1), maternal smear positivity at the same visit (AOR = 3.5), history of infant fever in the previous two weeks (AOR = 2.8), birth during the rainy season (AOR = 1.7), low socioeconomic status (AOR = 1.6), and low maternal education (AOR = 1.5). The specificity of a recent fever history for malaria infection in early infancy was high (> 70%). Intervention strategies to reduce the risk of early infant infection need to be targeted toward mothers of infants at high risk.

Evaluation of maternal practices, efficacy, and cost-effectiveness of alternative antimalarial regimens for use in pregnancy: chloroquine and sulfadoxine-pyrimethamine

With the knowledge that an efficacious antimalarial administered to pregnant women would markedly reduce placental malaria and its associated risk of low birth weight (LBW), investigations were conducted to identify an antimalarial regimen practical for nationwide implementation through the antenatal clinic (ANC) system. Maternal practices, including ANC utilization and malaria treatment and prevention during pregnancy were evaluated as part of a national malaria knowledge, attitudes, and practices survey. A second study was conducted to evaluate the efficacy and cost of selected alternative antimalarial regimens. Women in their first or second pregnancy were placed on chloroquine (CQ) treatment (25 mg/kg) followed by weekly CQ (300 mg) (CQ/CQ); sulfadoxine-pyrimethamine (SP) treatment followed by CQ (300 mg weekly) (SP/CQ); or SP treatment during the second trimester and repeated at the beginning of the third trimester (SP/SP). With 87% of women attending ANC two or more times during pregnancy, most pregnant women in Malawi could be reached with an antimalarial intervention. Among 159 women in their first or second pregnancy receiving CQ/CQ, SP/CQ, and SP/SP, placental malaria parasitemia rates were 32%, 26%, and 9%, respectively (P = 0.006, by chi-square test). The SP/SP regimen was also markedly more cost-effective in preventing infant deaths, costing $75 per infant death prevented, compared with $481 for SP/CQ and $542 for CQ/CQ. These investigations suggest that a regimen consisting of two treatment doses of SP during pregnancy is an efficacious and cost-effective intervention to prevent placental malaria, and LBW-associated mortality, that can be delivered to pregnant women through ANCs in settings similar to those found in rural Malawi.

Testing strategies to increase use of chloroquine chemoprophylaxis during pregnancy in Malaŵi

The widespread problem of low and non-compliance to antimalarial chemoprophylaxis during pregnancy demands that attention be focused on alternative approaches to programming, product acceptability and demand for preventive services. This study describes the testing of three interventions to determine their effect on use of chloroquine (currently the most widely used drug for chemoprophylaxis) during pregnancy. The strategies evolved from community-based formative research undertaken to learn about the local concept of malaria and issues surrounding malaria prevention and treatment during pregnancy. The resulting interventions were tested in four clinics, and included a change in the health education message given during antenatal sessions, distribution of a sugar-coated chloroquine tablet, and an intervention combining the two strategies. The results showed a 45% increase in chloroquine use when the health education message was changed, and a 64% increase when the product was changed. High use levels were maintained with the combined intervention; an additive effect was seen. The study shows that improving the product was the most important factor in increasing the use of the program, and that changing the health education message can also make an impact on use.

The efficacy of antimalarial regimens containing sulfadoxine-pyrimethamine and/or chloroquine in preventing peripheral and placental Plasmodium falciparum infection among pregnant women in Malawi

To define an effective and deliverable antimalarial regimen for use during pregnancy, pregnant women at highest risk of malaria (those in their first or second pregnancy) in an area of Malawi with high transmission of chloroquine (CQ)-resistant Plasmodium falciparum were placed on CQ and/or sulfadoxine-pyrimethamine (SP). Of 38 pregnant women who received CQ treatment followed by weekly CQ prophylaxis (CQ/CQ) for at least 45 days prior to delivery, 32% had placental malaria infection, compared with 26% of 50 pregnant women who received a treatment dose of SP followed by weekly CQ prophylaxis (SP/CQ), and only 9% of 71 pregnant women who received a two-dose SP regimen (SP/SP; given once during the second trimester and repeated at the beginning of the third trimester) (P = 0.006, by chi-square test). During the peak transmission season from April to July, 47% of the women who received CQ/CQ had placental malaria infection at delivery, as compared with 37% of the women who received SP/CQ, and 10% of women who received SP/SP (P = 0.004, by chi-square test). Among women in their first or second pregnancy, two treatment doses of SP were highly effective in decreasing the proportion of women with placental malaria infection at delivery.

Malaria knowledge, attitudes and practices in Malawi: survey population characteristics

A national knowledge, attitudes and practices (KAP) survey was conducted in March-April 1992 to examine malaria illness and the people's response to illness and malaria prevention. Fifty-one households in each of 30 randomly selected communities were sampled and information was recorded from 1,531 households and 7,025 individuals. The population is characterized by low income (average household and per capita income were US $490 and $122, respectively) and low education levels (among adult women, 45% had no formal education and only 3.9% completed more than 8 years of schooling). Characteristics of the population were similar to those found in the 1987 national census, suggesting that the survey population was representative of the larger population of Malawi. Children under 5 years of age made up 15.8% of the population and had the highest rates of fever illness; these children experienced an estimated 9.7 cases/year of fever illness consistent with malaria. Although adults reported fever less frequently, women of reproductive age experienced an estimated 6.9 episodes of fever annually. The burden of malaria morbidity in this population is extremely high and occurs in all age groups.

A nation-wide malaria knowledge, attitudes and practices survey in Malawi: objectives and methodology

A malaria knowledge, attitudes and practices survey was conducted in Malawi during April and May, 1992, to provide policy makers and program managers with information needed to design or improve malaria control programs, to establish epidemiologic and behavioral baselines, and to identify indicators for monitoring program effectiveness. Using cluster-sample survey methodology, 1531 households, in 30 clusters of 51-52 households each, were identified and members interviewed. Interviews were conducted by trained survey teams composed of young Malawian women with secondary level education. Heads of households were asked about malaria prevention methods used and about household economics; caretakers of children were asked about treatment and health seeking behavior in a recent malaria episode in a child; and women who had been pregnant in the past 5 years were asked about their antenatal clinic utilization and malaria during pregnancy. Survey results will be used to make programmatic decisions, including developing health education messages and establishing monitoring and evaluation of malaria control activities and outcomes in Malawi.

Malaria and childbearing women in Malawi: knowledge, attitudes and practices

Information on women's use of antenatal clinic (ANC) service, including malaria prevention and treatment during pregnancy, was collected during a national malaria knowledge, attitudes, and practices survey in Malawi. Among 1531 households, 809 (53%) included a woman who had carried a pregnancy past the second trimester within the past 5 years. Of these, 756 (93%) women reported at least one ANC visit during pregnancy (median = 4); 336 (42%) attended 5 or more times. Approximately half (51%) reported delivering in a hospital; 5% delivered in a clinic; 13% delivered at home with a trained birth attendant; and 28% delivered at home with only family attending. Women at increased risk for delivery complications (e.g. primigravidas and grand multigravidas) were no more likely to attend ANC or deliver in hospital than women without increased risk. The woman's level of education was the only significant predictor of initiating ANC care, continued ANC attendance, and delivery in hospital. In a setting where 43% of women pregnant within the past 5 years had received no formal education and 70% had completed less than 5 years, this survey identified a critical need for targeting health messages towards poorly educated women to ensure proper utilization of antenatal care services, including coverage with malaria prevention throughout pregnancy.

Treatment of malaria fever episodes among children in Malawi: results of a KAP survey

Caretakers of children (< 10 years of age) were questioned about management of pediatric malarial fever episodes in a nation-wide knowledge, attitudes, and practices survey conducted in Malawi. A total of 1,531 households in 30 randomly selected clusters of 51 households each were sampled and interviewed. Overall 557 caretakers reported a fever in their child in the previous 2 weeks; 43%-judged the illness as severe. Fifty-two percent of caretakers brought their febrile children to clinic. Clinic attendance was positively correlated with young age of the child (< 4 years), severe illness, and higher socioeconomic status. Seventy-four percent of clinic attenders gave their child an antimalarial; in contrast, only 42% of those not attending clinic gave an antimalarial. Optimal therapy (administration of an antimalarial promptly and at the proper dosage) was received by only 7% of febrile children. Children taken to clinic were twice as likely to receive optimal therapy as were non-attenders. Identification of critical points in the optimal therapy algorithm and characteristics of caretakers linked with sub-optimal therapy may help malaria control programs target specific groups and health education messages to improve treatment of malaria fever episodes.

Oral rehydration therapy in Malawi: impact on the severity of disease and on hospital admissions, treatment practices, and recurrent costs

In the first 2 years following refresher training of paediatric staff in oral rehydration therapy (ORT) and the establishment of an oral rehydration unit at the Kamuzu Central Hospital, Lilongwe, Malawi, there was a 50% decrease in the number of children admitted to the paediatric ward with the diagnosis of diarrhoeal diseases, a 56% decrease in the use of intravenous fluid to rehydrate such children, a threefold increase in the use of oral rehydration salts (ORS) exclusively to rehydrate children with mild or moderate dehydration, and a 39% decrease in the number of paediatric deaths associated with diarrhoeal diseases. Over the same period, there was a 32% decrease in recurrent hospital costs attributable to paediatric diarrhoeal diseases. As use of ORT continues to increase in Malawi, where diarrhoeal diseases account for 9% of paediatric hospital admissions, there should be considerable decreases in mortality from such diseases and concomitant increases in cost savings attributable to them.