Incidence Of Malaria Episodes Research Articles

Differential impact of malaria control interventions on P. falciparum and P. vivax infections in young Papua New Guinean children

IntroductionAs malaria transmission declines, understanding the differential impact of intensified control on Plasmodium falciparum relative to Plasmodium vivax and identifying key drivers of ongoing transmission is essential to guide future interventions.MethodsThree longitudinal child cohorts were conducted in Papua New Guinea before (2006/2007), during (2008) and after scale-up of control interventions (2013). In each cohort, children aged 1–5 years were actively monitored for infection and illness. Incidence of malaria episodes, molecular force of blood-stage infections (molFOB) and population-averaged prevalence of infections were compared across the cohorts to investigate the impact of intensified control in young children and the key risk factors for malaria infection and illness in 2013.ResultsBetween 2006 and 2008, P. falciparum infection prevalence, molFOB, and clinical malaria episodes reduced by 47%, 59% and 69%, respectively, and a further 49%, 29% and 75% from 2008 to 2013 (prevalence 41.6% to 22.1% to 11.2%; molFOB: 3.4 to 1.4 to 1.0 clones/child/year; clinical episodes incidence rate (IR) 2.6 to 0.8 to IR 0.2 episodes/child/year). P. vivax clinical episodes declined at rates comparable to P. falciparum between 2006, 2008 and 2013 (IR 2.5 to 1.1 to 0.2), while P. vivaxmolFOB (2006, 9.8; 2008, 12.1) and prevalence (2006, 59.6%; 2008, 65.0%) remained high in 2008. However, in 2013, P. vivaxmolFOB (1.2) and prevalence (19.7%) had also substantially declined. In 2013, 89% of P. falciparum and 93% of P. vivax infections were asymptomatic, 62% and 47%, respectively, were sub-microscopic. Area of residence was the major determinant of malaria infection and illness.ConclusionIntensified vector control and routine case management had a differential impact on rates of P. falciparum and P. vivax infections but not clinical malaria episodes in young children. This suggests comparable reductions in new mosquito-derived infections but a delayed impact on P. vivax relapsing infections due to a previously acquired reservoir of hypnozoites. This demonstrates the need to strengthen implementation of P. vivax radical cure to maximise impact of control in co-endemic areas. The high heterogeneity of malaria in 2013 highlights the importance of surveillance and targeted interventions to accelerate towards elimination.

Malaria Incidence Does Not Differ with Immediate Compared to 28-day Delayed Iron Treatment in Children with Severe Malaria and Iron Deficiency (OR10-04-19)

ObjectivesWe aimed to determine if delaying iron until 28 days after antimalarial treatment in children with severe malaria and iron deficiency leads to fewer subsequent clinical malaria episodes as compared to concurrent iron therapy. MethodsThe randomized controlled trial was conducted Ugandan children 18 mo-5 y with severe malaria [cerebral malaria (CM), n = 79; severe malarial anemia (SMA), n = 77] and healthy community children (CC, n = 83) at Mulago Hospital in Kampala, Uganda. All children with malaria received antimalarial treatment. Children with iron deficiency (defined by zinc protoporphyrin (ZPP) >= 80 μmol/mol heme) were randomized to start a 90-day course of ferrous sulfate (2 mg/kg/day) concurrently with antimalarial treatment on Day 0 (immediate group, I) or on Day 28 (delayed group, D). Incidence of malaria episodes over the 12-month follow-up period was assessed by sick-child visits to the study clinic. Malaria was defined as measured fever (T >37.5°C) plus Plasmodium falciparum on blood smear. Negative binomial regression was used to model counts of malaria episodes as a function of treatment group (I or D), controlling for age. Hazard ratios compared time to event between the I and D groups. ResultsAll children with CM and SMA and 35 CC had high ZPP and were randomized to I or D iron. There were no differences in malaria incidence (defined with either measured fever or history of fever) with I vs. D treatment in any study group. The incidence of inpatient malaria episodes defined with history of fever was marginally statistically significant lower with D iron in the SMA group [incidence rate ratio (IRR) D/I (95% CI) = 0.38 (0.14, 1.1), P = 0.07). In the SMA group, children who received D iron tended to have a longer time to first inpatient event than children in the I group [Hazard ratio (95% CI) D/I: 0.37 (0.13, 1.1), P = 0.07]. ConclusionsDelaying iron in children with severe malaria had no clear risk or benefit on subsequent malaria incidence or time-to-first episode as compared to immediate treatment. Given that previous analysis revealed that iron status was improved with delayed iron among children with SMA, the lack of difference in malaria incidence suggests that delaying iron therapy may be a safe way to improve iron status in this group. Funding SourcesNIH/NICHD.

Impact of combining intermittent preventive treatment with home management of malaria in children less than 10 years in a rural area of Senegal: a cluster randomized trial

BackgroundCurrent malaria control strategies recommend (i) early case detection using rapid diagnostic tests (RDT) and treatment with artemisinin combination therapy (ACT), (ii) pre-referral rectal artesunate, (iii) intermittent preventive treatment and (iv) impregnated bed nets. However, these individual malaria control interventions provide only partial protection in most epidemiological situations. Therefore, there is a need to investigate the potential benefits of integrating several malaria interventions to reduce malaria prevalence and morbidity.MethodsA randomized controlled trial was carried out to assess the impact of combining seasonal intermittent preventive treatment in children (IPTc) with home-based management of malaria (HMM) by community health workers (CHWs) in Senegal. Eight CHWs in eight villages covered by the Bonconto health post, (South Eastern part of Senegal) were trained to diagnose malaria using RDT, provide prompt treatment with artemether-lumefantrine for uncomplicated malaria cases and pre-referral rectal artesunate for complicated malaria occurring in children under 10 years. Four CHWs were randomized to also administer monthly IPTc as single dose of sulphadoxine-pyrimethamine (SP) plus three doses of amodiaquine (AQ) in the malaria transmission season, October and November 2010. Primary end point was incidence of single episode of malaria attacks over 8 weeks of follow up. Secondary end points included prevalence of malaria parasitaemia, and prevalence of anaemia at the end of the transmission season. Primary analysis was by intention to treat. The study protocol was approved by the Senegalese National Ethical Committee (approval 0027/MSP/DS/CNRS, 18/03/2010).ResultsA total of 1,000 children were enrolled. The incidence of malaria episodes was 7.1/100 child months at risk [95% CI (3.7-13.7)] in communities with IPTc + HMM compared to 35.6/100 child months at risk [95% CI (26.7-47.4)] in communities with only HMM (aOR = 0.20; 95% CI 0.09-0.41; p = 0.04). At the end of the transmission season, malaria parasitaemia prevalence was lower in communities with IPTc + HMM (2.05% versus 4.6% p = 0.03). Adjusted for age groups, sex, Plasmodium falciparum carriage and prevalence of malnutrition, IPTc + HMM showed a significant protective effect against anaemia (aOR = 0.59; 95% CI 0.42-0.82; p = 0.02).ConclusionCombining IPTc and HMM can provide significant additional benefit in preventing clinical episodes of malaria as well as anaemia among children in Senegal.

Malaria morbidity in children in the year after they had received intermittent preventive treatment of malaria in Mali: a randomized control trial.

BackgroundIntermittent preventive treatment of malaria in children (IPTc) is a promising strategy for malaria control. A study conducted in Mali in 2008 showed that administration of three courses of IPTc with sulphadoxine-pyrimethamine (SP) and amodiaquine (AQ) at monthly intervals reduced clinical malaria, severe malaria and malaria infection by >80% in children under 5 years of age. Here we report the results of a follow-on study undertaken to establish whether children who had received IPTc would be at increased risk of malaria during the subsequent malaria transmission season.MethodsMorbidity from malaria and the prevalence of malaria parasitaemia and anaemia were measured in children who had previously received IPTc with SP and AQ using similar surveillance methods to those employed during the previous intervention period.Results1396 of 1508 children (93%) who had previously received IPTc and 1406 of 1508 children (93%) who had previously received placebos were followed up during the high malaria transmission season of the year following the intervention. Incidence rates of clinical malaria during the post-intervention transmission season (July –November 2009) were 1.87 (95% CI 1.76 –1.99) and 1.73 (95% CI; 1.62–1.85) episodes per child year in the previous intervention and placebo groups respectively; incidence rate ratio (IRR) 1.09 (95% CI 0.99 –1.21) (P = 0.08). The prevalence of malaria infection was similar in the two groups, 7.4% versus 7.5%, prevalence ratio (PR) of 0.99 (95% CI 0.73–1.33) (P = 0.95). At the end of post-intervention malaria transmission season, the prevalence of anaemia, defined as a haemoglobin concentration<11g/dL, was similar in the two groups (56.2% versus 55.6%; PR = 1.01 [95% CI 0.91 – 1.12]) (P = 0.84).ConclusionIPTc with SP+AQ was not associated with an increase in incidence of malaria episodes, prevalence of malaria infection or anaemia in the subsequent malaria transmission season.Trial RegistrationClinicalTrials.gov NCT00738946

The effects of a pre-season treatment with effective antimalarials on subsequent malaria morbidity in under five-year-old children living in high and seasonal malaria transmission area of Burkina Faso

To evaluate the effects of pre-season treatment with single dose of sulfadoxine-pyrimethamine (SP) or artemether-lumefantrine (AL) on subsequent malaria morbidity in under-fives. A cohort of 156 children was enrolled for longitudinal follow-up. Children received curative therapy with SP or AL, and a third group received no treatment. Participants were home-visited twice a week with blood smears taken from children with fever (axillary T° ≥ 37.5 °C) or history of fever. To assess the time to re-infection, a blood film was also systematically obtained from pre-treated children every 2 weeks. The mean time to the first malaria infection was 36 days in the SP arm and 26 days in the AL arm (P=0.006). The incidence density of malaria infection was similar in both groups (86.5%vs. 92.3%, P=0.52). The mean time to the first malaria episode was 47 days in the SP arm and 32 days in the AL arm (P<0.001). The incidence of malaria episodes was significantly higher in the group pre-treated with AL (45.7 per 1000 child days-at-risk CI 95% [35-56]) than in the control group (10.7 per 1000 child days-at-risk CI 95% [7-15]); P<0.001). Our findings suggest that the radical clearance of parasitemia with AL may increase susceptibility to malaria infection and clinical malaria episodes.

Indoor residual spraying for preventing malaria.

BACKGROUND: Primary malaria prevention on a large scale depends on two vector control interventions: indoor residual spraying (IRS) and insecticide-treated mosquito nets (ITNs). Historically, IRS has reduced malaria transmission in many settings in the world, but the health effects of IRS have never been properly quantified. This is important, and will help compare IRS with other vector control interventions. OBJECTIVES: To quantify the impact of IRS alone, and to compare the relative impacts of IRS and ITNs, on key malariological parameters. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group Specialized Register (September 2009), CENTRAL (The Cochrane Library 2009, Issue 3), MEDLINE (1966 to September 2009), EMBASE (1974 to September 2009), LILACS (1982 to September 2009), mRCT (September 2009), reference lists, and conference abstracts. We also contacted researchers in the field, organizations, and manufacturers of insecticides (June 2007). SELECTION CRITERIA: Cluster randomized controlled trials (RCTs), controlled before-and-after studies (CBA) and interrupted time series (ITS) of IRS compared to no IRS or ITNs. Studies examining the impact of IRS on special groups not representative of the general population, or using insecticides and dosages not recommended by the World Health Organization (WHO) were excluded. DATA COLLECTION AND ANALYSIS: Two authors independently reviewed trials for inclusion. Two authors extracted data, assessed risk of bias and analysed the data. Where possible, we adjusted confidence intervals (CIs) for clustering. Studies were grouped into those comparing IRS with no IRS, and IRS compared with ITNs, and then stratified by malaria endemicity. MAIN RESULTS: IRS versus no IRSStable malaria (entomological inoculation rate (EIR) 1): Two studies; for incidence and prevalence, the malaria rates were higher in the IRS group compared to the ITN group in one study. Malaria incidence was higher in the IRS arm in India (risk ratio IRS:ITN = 1.48) and in South Africa (risk ratio 1.34 but the cluster unadjusted CIs included 1). For malaria prevalence, ITNs appeared to give better protection against any infection compared to IRS in India (risk ratio IRS:ITN = 1.70) and also for both P. falciparum (risk ratio IRS:ITN = 1.78) and P. vivax (risk ratio IRS:ITN = 1.37). AUTHORS' CONCLUSIONS: Historical and programme documentation has clearly established the impact of IRS. However, the number of high-quality trials are too few to quantify the size of effect in different transmission settings. The evidence from randomized comparisons of IRS versus no IRS confirms that IRS reduces malaria incidence in unstable malaria settings, but randomized trial data from stable malaria settings is very limited. Some limited data suggest that ITN give better protection than IRS in unstable areas, but more trials are needed to compare the effects of ITNs with IRS, as well as to quantify their combined effects

Does treatment of intestinal helminth infections influence malaria? Background and methodology of a longitudinal study of clinical, parasitological and immunological parameters in Nangapanda, Flores, Indonesia (ImmunoSPIN Study)

BackgroundGiven that helminth infections are thought to have strong immunomodulatory activity, the question whether helminth infections might affect responses to malaria antigens needs to be addressed. Different cross-sectional studies using diverse methodologies have reported that helminth infections might either exacerbate or reduce the severity of malaria attacks. The same discrepancies have been reported for parasitemia.Methods/DesignTo determine the effect of geohelminth infections and their treatment on malaria infection and disease outcome, as well as on immunological parameters, the area of Nangapanda on Flores Island, Indonesia, where malaria and helminth parasites are co-endemic was selected for a longitudinal study. Here a Double-blind randomized trial will be performed, incorporating repeated treatment with albendazole (400 mg) or placebo at three monthly intervals. Household characteristic data, anthropometry, the presence of intestinal helminth and Plasmodium spp infections, and the incidence of malaria episodes are recorded. In vitro cultures of whole blood, stimulated with a number of antigens, mitogens and toll like receptor ligands provide relevant immunological parameters at baseline and following 1 and 2 years of treatment rounds. The primary outcome of the study is the prevalence of Plasmodium falciparum and P. vivax infection. The secondary outcome will be incidence and severity of malaria episodes detected via both passive and active follow-up. The tertiary outcome is the inflammatory cytokine profile in response to parasite antigens. The project also facilitates the transfer of state of the art methodologies and technologies, molecular diagnosis of parasitic diseases, immunology and epidemiology from Europe to Indonesia.DiscussionThe study will provide data on the effect of helminth infections on malaria. It will also give information on anthelminthic treatment efficacy and effectiveness and could help develop evidence-based policymaking.Trial registrationThis study was approved by The Ethical Committee of Faculty of Medicine, University of Indonesia, ref:194/PT02.FK/Etik/2006 and has been filed by ethics committee of the Leiden University Medical Center. Clinical trial number:ISRCTN83830814. The study is reported in accordance with the CONSORT guidelines for cluster-randomized studies.

Malaria preventive measures, health care seeking behaviour and malaria burden in different epidemiological settings in Sudan

To provide information about preventive measures and treatment seeking behaviour as well as an estimate of the malaria burden in different epidemiological settings for effective monitoring and evaluation of the ongoing efforts. Cross-sectional survey carried out in four areas representing different levels of transmission to explore the use of preventive measures, care-seeking behaviour and accessibility in addition to point prevalence was followed by a follow-up phase in which the health workers registered and reported all fever cases including malaria. The relation between the reported malaria incidence, the product of symptomatic/asymptomatic ratio and the prevalence of confirmed malaria cases was used to develop the equation that could predict the true malaria incidence. Thousand households and 3628 individuals were surveyed. The presence of any net varied between 6.6% and 40%; the percentage of people who reportedly slept under mosquito nets in the previous night varied between 35 and 80. Prompt use of medications ranged between 14 and 48% with a delay of more than 24 h noticed in different areas. The mean number of individuals per household who reported use of anti-malarial drugs in the last 2 weeks ranged between 0.6 (SD = 0.92) and 1.2 (SD = 1.1), with variable cost per treatment and affordability. The prevalence of asymptomatic parasitaemia, fever and confirmed malaria at time of the survey differed by area. The incidence of malaria during the follow-up period was estimated to be 8.5, 178.6, 23.7 and 10.3 episodes per 1000 population in Malakal, Elrank, Elhosh and El Matama, respectively. Based on this, a prediction equation was developed. We found suboptimal health care seeking behaviour, coverage and use of preventive measures with a high malaria burden. We developed a model for future estimation of malaria episodes.

ASSOCIATION OF SCHISTOSOMA HAEMATOBIUM INFECTION WITH PROTECTION AGAINST ACUTE PLASMODIUM FALCIPARUM MALARIA IN MALIAN CHILDREN

Plasmodium falciparum and Schistosoma haematobium are co-endemic parasitic diseases with worldwide distribution. Evidence suggests interactions occur between helminthic and malaria infections, although it is unclear whether this effect is beneficial or harmful to the host. Malian children 4-14 years of age with asymptomatic S. haematobium infection (SP) (n = 338) were prospectively matched by age, sex, and residence to children without schistosomiasis (SN) (n = 338) who were cleared of occult intestinal parasites, and followed-up for one malaria transmission season (25 weeks). The time to the first clinical malaria infection, incidence of malaria episodes, and parasitemia were recorded. Age associated protection from malaria in children with schistosomiasis was observed. SP children (4-8 years of age) compared with SN children demonstrated delayed time to first clinical malaria infection (74 versus 59 days; P = 0.04), fewer numbers of malaria episodes (1.55 versus 1.81 infections; P = 0.03) and lower geometric mean parasite densities (6,359 versus 9,874 asexual forms/mm(3); P = 0.07) at first infection. No association between schistosomiasis and P. falciparum malaria was observed in children 9-14 years of age. We conclude that underlying schistosomiasis is associated with protection against clinical falciparum malaria in an age-dependent manner.

The contribution of repellent soap to malaria control.

A study about the acceptability, protective efficacy, effectiveness, and cost of a repellent soap containing 20% diethyltoluamide and 0.5% permethrin was carried out on the Pacific coast of Ecuador and Peru, where malaria is endemic and the transmission is seasonal. The malaria vectors were Anopheles albimanus, An. punctimacula, and An. pseudopunctipennis in Ecuador and An. albimanus in Peru. Comparing the hourly mosquito bites on human subjects with and without the protection of the repellent soap, it showed that inactive, protected subjects were bitten 94.2% less than unprotected controls 2 hr after application of the soap. This protective efficacy was reduced to 81% after 6 hr. In persons physically active for 3 hr after application, the efficacy of the soap was 67% in the fourth hour after application and 52% in the sixth hour after application. Sweating decreased the protective efficacy of the soap even more. In a community-based malaria control program, the soap was introduced by community health promoters. Acceptance was good when it was given free of charge but reduced dramatically when it was sold. People used the soap mainly because of the nuisance of mosquitoes. The application was generally done correctly. However, no significant impact on the incidence of malaria episodes could be shown when comparing intervention communities with control communities, either in Ecuador, where the proportion of Plasmodium falciparum cases was high, or in Peru, where P. vivax was the only species of Plasmodium seen. This can probably be explained by the limited use of soap and the shift of mosquito bites from users to nonusers of the repellent soap. The cost of a soap program would be $4.60 (USA) per person per year, which seems to be quite high in terms of cost of soap and its distribution related to people's low cash income. The implications of the introduction of repellent soap into a control program are discussed.